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Old 03-09-2008, 08:00 PM   #1
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Why does my engine knock?? (video inside now)

I have always wondered why my engine knocks so much. I have new plugs, whole new distributor with all the stuff it needs new too, fuel filter, the injectors make a perfect cone. Basically, the motor runs almost perfect - except this.

It never has knocked when I am going WOT. It always happens right when I am letting the clucth out, and giving it gas to keep the motor running. Usually, right as I go to take off from a stop sign. It also does it anytime I start out in 2nd gear.

The only other times I have noticed it, is if I am cruising in like 4th gear, at a low speed like 35mph. If I really jab the gas to accelerate, in 4th still, it knocks for a split second, stops, and looses some power. I guess this must be the KR kicking in. Also it did it in 3rd today, I went to go WOT and it made just 2 little pings right before you could hear PE mode kick in.

Thanks
----------
oh, and I have the timing set at 0* advance, just like the sticker says. I have tried up to 6* advance, but that just makes it wayyy worse. Also, higher octain gas helps it, but I can still **make** it knock with high octain. That is irrelevant because I cant afford to fill up on premium, even 89 octain starts at way more than the price of regular. And 93 is even more than that.
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Old 03-10-2008, 09:31 AM   #2
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Re: Why does my engine knock??

Nobody knows??

Today I realized that I cant make it knock, unless its completely warmed up. I have a 180* stat in there too - so it keeps a little cooler.

However, last night, when I was idling for a while, it got up to 220.* When I was driving, I noticed that it was knocking the whole time I was cruising, under very little throttle. Then the temp got back down to 180, it stopped doing it. Does this mean I need a 170* maybe?

What temperature does the ECM get to closed loop? Because I thought 180 was the lowest possible.
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Old 03-10-2008, 03:07 PM   #3
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Re: Why does my engine knock??

Well, here is a video I took.

http://www.youtube.com/watch?v=XiBzxxvy3FQ
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Old 03-10-2008, 03:44 PM   #4
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Re: Why does my engine knock??

did you check your timing? have you fiddled with it?
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Old 03-10-2008, 03:52 PM   #5
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Re: Why does my engine knock??

He says it's at zero, worse at six. Slipped ring/verify TDC?

EST should throw a code for the later TBI's if the KS fails. Supposed to run a self test at start up. Even if you showed the code (43?) the ecm is supposed to seriously retard timing when it fails.
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Old 03-10-2008, 03:56 PM   #6
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Re: Why does my engine knock??

ive seen this many times in the past....its labor knocking......try bumping the timing back or a higher grade of gas...good luck...
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Old 03-10-2008, 04:20 PM   #7
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Re: Why does my engine knock??

Well I was outside just now, playing with the timing. When I took that video, it was indeed at 0* TDC. I then retarded the timing even more too 3* ATDC. It got slightly better, but still made the nosie pretty bad. Also lost alot of power, expecially in higher RPMs. Then, I unplugged the ESC wire, and drove around with it unplugged. That alone should eliminate ANY timing advance, right?

Well, with the ESC unplugged, it was definately a dog. Made alot of sucking nosie when I opened the throttle, like a huge fan, but didnt go anywhere. When I was driving with the wire unplugged, it knocked worse than ever. It made that same noise from the video, except it did it the whole way up a hill, at less than 1/2 throttle.

Now that is where I am confused. Why would it do that with no timing advance? When I got home, I reset it to 0*, then changed my mind, and advanced it to 3* BTDC. Went for another ride, and its only as bad as it was in the video again, except I can still pick up faint pinging noises during cruise and acceleration, but I really have to listen for it.
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Old 03-10-2008, 04:37 PM   #8
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Re: Why does my engine knock??

you could also have a very worn timing chain or a distributor....its a process of
elimination one of these or a combonation of the two will throw your timing off and it to labor knock.
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Old 03-10-2008, 04:44 PM   #9
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Re: Why does my engine knock??

Well, the motor has 57k miles. Timing chain should be fine.

I put in a new stock replacment distributor last fall. Used the old one as a core charge, because the cap screws sheared off in the base. It was the origional cap and rotor at over 50k miles, so I just said f**k it, and bought a whole new one.

Maybe the gas is just getting really bad lately. When I was filling up in NH, I used regular up there, and even though it occasionally did it, it was few and far between, and the motor had more power on NH gas.

I think tonight I might go to one of the *non-value brand* gas stations, and try some 93 octain.
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Old 03-10-2008, 06:24 PM   #10
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Re: Why does my engine knock??

With the EST/BYPASS connector open there is still some spark advance. As part of the limp mode in the ignition module there is a built in 12 to 16 degrees of advance. This comes in someplace around 1400 - 1800 RPM.

Can see this with a light as the RPMs are increased.

It may be there is carbon build up in the chambers. Plug wires on the incorrect cylinders, or as mentioned above the damper slipped.

At WOT/PE mode the ECM will add timing to force the engine to knock. This is part of the diagnostic routines. If knock occures the test is not run again until the next key-on.

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Old 03-10-2008, 07:12 PM   #11
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Re: Why does my engine knock??

i dont believe a slipped ring. i would seafoam and then pull plugs for a reading.. when you retarded the timing and the engine lost power but still knocked probably means that you might have low fuel preassue or the beginnigs of clogged egr passages. also could be a clogged cat. might need to pull the intake to really get the egr clean if thats what it is. its worth doing because a properly working egr helps with fuel economy. if you have the ability to datalog then post it up.
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Old 03-10-2008, 07:12 PM   #12
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Re: Why does my engine knock??

Thanks, Rbob. I dont think the damper has slipped. Personally, I have never touched it. Also, as I am shooting the gun at it, and turning the dist, I can hear the engine react to the timing change. I can hear it get a smoother, cleaner sounding idle towards 6* advance, at 0* TDC it gets a little rougher, and surges up and down a little in the RPMs (only with the wire unplugged). As I start to retard it past 0*, towards the lower end of the indicator, it starts smelling of rich exhaust in the garage, and the idle starts surging more dramatically like it wants to stall.

I am 99.99% sure that the plug wires are on the right cylinders, because I am still running the origional "Packard" wires that have a cyl.# on each wire. I thought about replacing them once, but these ones are pretty mint, and I love the #'s on each wire, makes it easy to keep track of.

So, you are saying that the first time you go WOT after key-on, it will always force knock?

Also, theoretically, what if I were to retard the timing to where I estimate 16* ATDC would be, because its not on the tab? Would that eliminate the knock?

I just cleaned the motor using water and carb cleaner yesterday. Maybe I will try a can of sea-foam, I havent done that since about October. I dont think I have deposits.

Finally, I was reading a site I found on google, about detonation, vs. pre-ignition. I have come to the conclusion that I am suffering from Detonation, not pre-ignition. That said, he noted that on some older motors, with "slow-burning" chambers, it is necessary to actually advance the timing a certain amount, in order to have the mixture be completley burned by 14* ATDC. He said, sometimes without enough advance, the fuel wont have time to all burn before the detonation can occur. Does this make sense to anyone????

I just dont understand how this can be happening. It's a low milage motor, I am under the hood at least every other day, if not every day, I change oil every 2,000 miles. I run carb cleaner, water, seafoam, or both, through it at least once every month or two, to clean the deposits. If my stock LO3 is pinging, I would hate to imagine what will happen if I try to build it with heads, LT1 cam, intake, exhaust, and an EBL.

I think this week, I need to pull a few spark plugs, and check their condition. Do you guys know how much damage an LO3 is gonna see from detonation, like in my video, a few times a day? And intermitten while cruising?

The last resort I can think of doing, is running a constant source of vacuum to the EGR valve. I read that the exhaust gasses to a great job of reducing tendancy to ping.
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Old 03-10-2008, 07:18 PM   #13
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Re: Why does my engine knock??

Quote:
Originally Posted by rocko350 View Post
i dont believe a slipped ring. i would seafoam and then pull plugs for a reading.. when you retarded the timing and the engine lost power but still knocked probably means that you might have low fuel preassue or the beginnigs of clogged egr passages. also could be a clogged cat. might need to pull the intake to really get the egr clean if thats what it is. its worth doing because a properly working egr helps with fuel economy. if you have the ability to datalog then post it up.
Doesent the EGR only open up, to help out lean cruise? I thought it wasnt used around town, like stopsign to stopsign. I put out the idea of trying to keep it open using constant vacuum tho.

Clogged cat? Could that cause this ping and knock? I thought it just basically stopped up the motor from accelerating.

As for datalogging, I have no way to do that. I have no money for software, or cables now. I was planning on ordering an EBL as a good first or second mod, but I have not been able to find work yet, so no cashola.
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Old 03-10-2008, 07:21 PM   #14
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Re: Why does my engine knock??

If you put a vacuum gauge on the motor what does it tell you?
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Old 03-10-2008, 07:32 PM   #15
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Re: Why does my engine knock??

IDK i dont got one. I can tell you it pulls vacuum, its got plenty to all the hoses little and big. Not like a radical cam, where there isnt enough vacuum for the brake booster.

Hey, I forgot to ask, where do you guys put the seafoam in? I have always poured it down the throttle bores. Should I be using the brake booster, or PCV hose?
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Old 03-10-2008, 09:06 PM   #16
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Re: Why does my engine knock??

Quote:
Originally Posted by slow_90firebird View Post
Thanks, Rbob. I dont think the damper has slipped. Personally, I have never touched it. Also, as I am shooting the gun at it, and turning the dist, I can hear the engine react to the timing change. I can hear it get a smoother, cleaner sounding idle towards 6* advance, at 0* TDC it gets a little rougher, and surges up and down a little in the RPMs (only with the wire unplugged). As I start to retard it past 0*, towards the lower end of the indicator, it starts smelling of rich exhaust in the garage, and the idle starts surging more dramatically like it wants to stall.

. . .

So, you are saying that the first time you go WOT after key-on, it will always force knock?

. . .
Once you re-connect the EST/BYPASS and restart the engine the timing advances to about 16 deg BTDC. The base setting is just to get the distributor base timing and ECM initial timing in sync.

For the WOT forced knock test the engine also needs to be up to temperature. If the 1st attempt to force knock fails the ECM will try at the next WOT. If that one also fails code 43 is tossed. If either passes then it is not run again until the next key-on.


Rocko's suggestion of EGR may be right on the money. When EGR is active the ECM pulls fuel & adds timing. If the EGR doesn't open it will ping like crazy. Can check this under the hood. Reach under the EGR 'dome' with your fingers until you can feel the diaphragm. Then open the thottle to 1200 - 1400 RPM. You should be able to feel the EGR opening.

It can also be clogged EGR passages. For this will need to remove the valve and look into the manifold.

The EGR is used a lot of the time. Actually, once the engine is up to temperature, except for idle, WOT, and decel it is active.

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Old 03-10-2008, 10:08 PM   #17
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Re: Why does my engine knock??

Well, I found a band-aid fix. It was getting so bad that it would ping while I was cruising, while I was accelerating, and I even think I heard one or 2 at idle. I needed to do something.

I went to the shell, which I normally wont buy gas at because its $.05 more for regular. I decided to try 93 octain, because 89 was $.25 cents more than 87, but 93 was only $.10 more than 89. I put in $20 of premium.

It was like instant fix. No more ping while driving, no more ping even starting off in 2nd gear. Well, it will ping a little if I let the clutch out too fast, and the RPM's get down to 200 or 300 rpm. But 300RPM + plenty of throttle = a bad combo anyway.

I cant afford to buy premium anymore. Plus, I want to find the real problem. I just dont see why a low compression, low performance, LO3, should need premium to run right. Doesent make sense.

I will check the EGR valve tomorrow with my finger. I am sure it works, I would probably be getting a code if it didnt, right? Also, do you guys know if they make a Rapidfire plug that is 1 step colder than stock?

Oh and thanks for all the help. It is much appreciated. I just hope I didnt permanently damage the engine, because I planned to keep the origional LO3 shortblock for the basis for future mods.
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Old 03-11-2008, 08:25 PM   #18
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Re: Why does my engine knock??

pushing the egr diaphram in with your finger at idle, if the engine stumbles when the egr is pushed, its moving exhaust into the intake and the egr valve is sealing when shut. if nothing happens then the egr passages are clogged and youll have a weekends work to do.

a fuel pressure check at this point will rule out a lot of stuff so if no guage , buy the adapter and permanent gague. 9-12 psi, but realistically these engines love 13 pounds. need to reiterate that a fuel ressure check needs to be done to rule out the fuel system.

you put the Seafoam in the brake booster line. run the engine til warm first(at idle is fine), hold your thumb over the tube and regulate the "leak" while pouring in the seafoam. pour in enough to let the engine stumble a little. just before the can runs out let it all go in and them shut the engine off and let it sit for 15-20 minutes. when it restarts it WILL smoke like hell. ive had the fire dept. show up at my shop because a neighbor thought the building was on fire. this was a 350,000 mile engine and an extreme case.

a fuel pressure check is still in order

you can get Seafoam in aerosol form with a really long straw to reach into the egr ports. but youll have to ask for it specifically
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Old 03-12-2008, 08:57 AM   #19
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Re: Why does my engine knock??

Yeah, I used to have a can of the "Deep Creep" before. It makes a good penetrating oil, and a decent carb cleaner, but its nothing like regular sea foam.

What is involved in cleaning the EGR passages? Just take off the valve, and get a toothbrush in there or something??

I did check to see if the EGR was working. I stuck my finger under there, and I could feel the diaphram moving when I slowly rolled on the throttle. However, I watched it and the little piston never moved in or out more than 1/8 of an inch or so... i dont know how much it really is supposed to move.

I still dont understand why putting premium in would make the problem all better. I am still running on that same $20 of it I put in, and it is getting crazy good gas milage around town compared to before. The motor makes som much power down low, that I dont have to put my leg in it around town any more.

But this motor was designed to run 87 octane, right? It should therefore perform just as good on 87 as it is doing now on 93!! Unless gas has changed "formulas" since the late 80's.

In case I didnt already say it - I have absoutely no codes or SES lights, so that must mean something.
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Old 03-12-2008, 10:20 AM   #20
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Re: Why does my engine knock??

Premium fuel is masking the problem. Higher octane is more resistant to knock and detonation. Since it's not knocking with the premium (at least not as much) the ecm is not retarding timing like it was with the 87. More timing = more power, better economy and a cooler running engine. Your engine is designed to run that way with 87 though so fix the problem and you'll save a butt load at the pump.

Do the EGR check outlined above. With it idling pull the diaphragm up and it should stumble.
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Old 03-12-2008, 01:53 PM   #21
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Re: Why does my engine knock??

Well I did the EGR test you mentioned. I pulled the diaphragm up, and it stumbled. Actually, jerked it up pretty hard, and the motor stalled.

However, I also preformed a test of my own. First I took full manifold vacuum, from idle, and applied it to the EGR valve. It caused the diaphragm to wobble back and forth, maybe 1/32" either way. But it never really opened it up at all, or anything. Even if I revved the motor, with full vacuum attached to the EGR valve, it didnt open up any more or less, just wobbled faster.

Then, I applied regular, computer controlled vacuum to the EGR valve (stock vacuum hose routing, vac to the electric thingy, then that has a hose to teh egr. With it hooked up like stock, if I revv the motor, it will open the EGR valve slightly, but not alot. Maybe 1/16" or a tiny bit more.

Does this mean that my EGR valve needs replacing? Because, if vacuum pressure is supposed to open it, but full idle vacuum doesent open it, then there might be a problem.

Here is the video of my EGR testing:

http://www.youtube.com/watch?v=x1MyOODy9W0


thanks for the continued help guys.
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Old 03-12-2008, 07:25 PM   #22
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Re: Why does my engine knock??

in you vid the engine didnt change in sound or rpm as far as i can tell. pushing on the egr diaphram had the desired effect. a change in idle charachteristics then return to staedy idle when released. i would renew the egr and fill up with 87 for "round 2". as a side note it doesnt sound like you need to "deep clean" the passages yet. maybe just some carb cleaner. dont forget to seafoam the engine. can only costs about 6 bucks. keep us posted.
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Old 03-12-2008, 08:14 PM   #23
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Re: Why does my engine knock??

There's a few different types of EGR valves used on these vehicles. Some valves require a change in exhaust backpressure to open completely. Applying vacuum to the valve isn't a definitive test. Manually operating the EGR valve and having the engine stumble does indicate that the passages are likely NOT clogged, but doesn't really tell us that the EGR valve is fully functional.

I've seen at least one manual that described comparing the force needed to manually open it to the force needed to open a new one as a test. Someone else may chime in with a more definitive test as I'd hate for you to spend around $60 or so on a new one and not need it.

If you do need a new one make sure to bring your old one in to make sure you get the correct replacement.
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Old 03-12-2008, 08:43 PM   #24
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Re: Why does my engine knock??

Well, first thing I would do is check fuel pressure like a few guys have said. From your description it sounds like its stumbling when AE should be invoked by the ECM, this is usually the point where the fuel demands are highest, so if you have a weak fuel pump it may not be able to supply the needed extra fuel in the AE/PE threshold when stepping into WOT.

Also, in the video, my car used to make that exact sound when I simply came off the clutch too early. It was hard to see the tach, but it looked like it could have been around 500RPM when you were coming off the clutch into gear. My vision may be deceiving me, but if that's correct just get the RPMs up higher before you come out of the clutch, like above 1k RPM. Low RPMs like that are very taxing on the engine when put into load.
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Old 03-12-2008, 10:39 PM   #25
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Re: Why does my engine knock??

I am pretty sure the fuel pressure is fine. Its such a PITA to check it, I would need to rent a guage, and get all the fittings to thread into where the filter goes. Changing the filter alone was like a 1 hr. job for me, trying to get the old one off, then thread the new one on when the lines each want to go their own way, the whole time I am loosing fuel to the floor, and getting it on my face. I dont feel like doing it, yet at least, when the car shows no signs of fuel starvation. It is running 100% perfect now that I ran that premium through it - tomorrow I will probably use more premium. I have been getting 16mpg around town, these last 3 days with premium. I can really granny the car now, not trying to keep the RPM's up. That is a decent improovment over 87 recently, but when I first got the car, I got like 18-20 around town, on 87, if I was easy on the throttle. Maybe a bad EGR, even without knock, would be detrimental to gas milage around town?

As for letting the clutch out too fast, well that might be it. Every time I start from a stop, I let the clutch out at about 600-700 RPM, and then it goes down to 500, then locks up and starts to climb again. In 2nd gear, I let it slip just a little longer, and it goes down to 400RPM. My buddie taught me about driving stick, to slip the clutch out at as low RPM as possible, and for a little time is necessary, and I wont waste clutch material. Kinda like how hitting the brakes at 100 is way worse than 65 or 70. Its all in RPMs and waste of material.

I cant afford an EGR valve just yet. The job I want, the boss wont call me back for the second interview, and he is never in when I call. So I have $200 in my account, and the Delphi replacement valve I want at NAPA is $90. And my brake pads are shot now too, the other one just started squealing today. I was surprised I got 10,000 miles out of the last 1/8" inch on them since I bought the car. I hardly ever use the brakes either, I just rev-match the motor, and down a gear to slow. I try not to use brakes above 15mph unless a crash is imminent.

I was at walmart today, where they have the $5 sea foam. It was out of stock. So I guess I gotta pay $7 at autozone now.
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Old 03-13-2008, 12:55 AM   #26
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Re: Why does my engine knock??

I have the SAME issue with my '92 Camaro with 115,000 miles. The only difference is I have an auto. I can't think of a SINGLE thing different. I've done the same tests, but just decided to keep premium in it, until about a month ago. I know, it's a band aid fix, but here, 93 is $0.20 more than 87.

I did notice that after every station plastered that they were selling E-10, that the issue did go away. Now, I can get away with 87 most of the time. I know the stated octane is the same, but the pinging isn't as bad.

One thing I have thought of is a lazy oxygen sensor. Not dead, but lazy.

And man, I feel your situation. Only here recently have I had the money to do anything more than pay my bills.

Ugh, now I want to go get some parts for my car and work on that issue since it wouldn't only help myself.
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Old 03-13-2008, 01:09 AM   #27
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Re: Why does my engine knock??

is E-10 10% ethanol? If so, thats all they sell in CT.

Im not too worried about it yet. It getting warmer soon, and I will get a job eventually, because I cant be needy. Even if I have to apply to autozone, or even worse, McDonalds.

It could be an O2 sensor, but I imagine it would throw a code for rich or lean exhaust. I have had that happen when my dizzy went bad - I got all kinds of codes.
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Old 03-13-2008, 10:04 AM   #28
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Re: Why does my engine knock??

Go to Autozone and get the cheapest brake pads they have. Should be $15. Put them on this weekend. If you absolutely can't do that right now, PM me and I'll send you a slightly used set, I've got several laying around.
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Old 03-13-2008, 01:32 PM   #29
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Re: Why does my engine knock??

When I said check fuel pressure I didn't mean the method you described, I've actually never heard of doing it that way. Install a fuel pressure gauge permanently using a T between the fuel lines in the engine compartment. I hit the point near the charcoal canister where the rubber line meets the hard line on the feed side. Put a T between the lines and put something like This in there
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Old 03-13-2008, 02:01 PM   #30
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Re: Why does my engine knock??

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Go to Autozone and get the cheapest brake pads they have. Should be $15. Put them on this weekend. If you absolutely can't do that right now, PM me and I'll send you a slightly used set, I've got several laying around.
Yeah, I will probably end up doing that. They will work fine untill I can afford nice rotors and metallic pads.


As for the fuel guage - I plan on upgrading the fuel pump to a better one eventually, and then install the aeromotive VAFPR with a guage right in my engine bay.
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Old 03-13-2008, 08:08 PM   #31
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Re: Why does my engine knock??

My LO3 (auto tranny) did the knock bad at 35-40mph--ran some seafoam through the gas tank, crankcase (oil), and the PCV vaccuum line as well as cleaned out my throttle body and it almost cleared up the really bad knock. It still knocks but you have to really pay attention to hear it.

This probably won't help you but it seemed to work for me. Then again I have 242,405 miles on my 305.
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Old 03-13-2008, 10:35 PM   #32
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Re: Why does my engine knock??

well I have already seafoamed the car twice in summer, and just before winter. Also have flooded the motor with carb cleaner and then started and steam cleaned with water a few times over winter (usually right before and oil change).
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Old 03-16-2008, 07:52 PM   #33
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Re: Why does my engine knock??

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well I have already seafoamed the car twice in summer, and just before winter. Also have flooded the motor with carb cleaner and then started and steam cleaned with water a few times over winter (usually right before and oil change).
Today I noticed with a full gas tank of 87 octane and 1pt (16oz) of Seafoam my knock has seemingly disappeared. You can BARELY hear it. I wonder if this in conjunction with using Seafoam in the vaccuum lines, crankcase (oil), and a tiny bit in the TB has somehow also helped in some way? Thoughts?

And is it possible to change your shift points on a automatoc + carb'd motor since you won't have an ECU? I'm new to carb so I need to learn some things.
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Old 03-16-2008, 08:31 PM   #34
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Re: Why does my engine knock??

Chances are, your seafoam treatment took out alot of the carbon deposits that cause detonation and increase compression.

I usually just suck almost the whole can in the vacuum line, and then dribble the last little bit down the TB now to clean the manifold after I shut it off.

I was thinking, does the fact that my car has bad valve seals, and smokes on startup, mean that I could be getting carbon deposits alot faster than most cars? If so, maybe I just need to make seafoam a more regualr thing.
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Old 03-16-2008, 08:40 PM   #35
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Re: Why does my engine knock??

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Chances are, your seafoam treatment took out alot of the carbon deposits that cause detonation and increase compression.

I usually just suck almost the whole can in the vacuum line, and then dribble the last little bit down the TB now to clean the manifold after I shut it off.

I was thinking, does the fact that my car has bad valve seals, and smokes on startup, mean that I could be getting carbon deposits alot faster than most cars? If so, maybe I just need to make seafoam a more regualr thing.
That's exactly what I thought since my valve seals are worn and I get the ultra-common oil runoff into the exhaust manifold--which = smoke on startup. I know its expensive, but, I usually buy 2 cans of Seafoam and use like you said almost all of the first one in the vaccuum lines and the little bit left into the throttle body. And I always use a can in the gas tank...this time was different as I also put it into my oil--with surprisingly awsome results. I wonder just how much compression I may have gained? The very first time I used Seafoam @ 230k miles it smoked ALOT which meant alot of carbon was built up. This time a fraction of the smoke came out--which means it was running fairly clean the last 12k miles.
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Old 03-16-2008, 09:08 PM   #36
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Re: Why does my engine knock??

i had the same issue when i still had TBI . but when ever the converter would lock up at low rpms

it seems to be one of the cylinders not getting the correct amount of fuel my guess as some older carb cars do the same
when i did my Tpi swap the "Knock" when away and hasnt come back my guess because it has injectors for every cylinder
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Old 03-17-2008, 10:10 PM   #37
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Re: Why does my engine knock??

if you had mentioned the smoking on startup i would have pointed out that the engine "see's" bad valve guides/seals as a vacuum leak and a point at which engine oil is introduced into the intake stream, much like an internally leaking intake gasket. this causes spark knock and carbon buildup. this is probably the fastest way to carbon up an engine except for running with a hole in a piston, or a broken ring. as a side note it is a real common failure. you might get way with another year with these heads if you put new valve guide seals in. not to mention power and economy will go up. also try removing each intake manifold t head bolt, put some rtv on the threads, and tighten them in the correct pattern.
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Old 04-05-2009, 05:22 PM   #38
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Re: Why does my engine knock??

i too had this same problem

i dont know if your car has the sme setup as my lg4 but if u have vaccuum lines running into the waterneck, try reversing them it worked for me
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Old 05-15-2009, 09:11 AM   #39
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Re: Why does my engine knock??

Amazing. Everything matches up.

I see the exact same symptoms on my engine. I have a little bit blue smoke on startup (comes out for 1 second at most), maybe a little more on hot days. I need to change the valve stem seals, that I know. I watched the video on youtube. On an easy startup, i hear the exact same sound in that video, but just for an instant. Also in WOT, after 4000 rpms I keep hearing the same knock, but this time continuously. Although the ones on start up and WOT have different immediate reasons, they're related. The little amount of oil in the chamber after sitting is causing the startup knock and the fast buildup of carbon on chamber surface because of the burning oil is causing the hard load knock after warming up.

I'm using 95 octane premium by the way. The company supports my fuel expenses, and the stations they have agreements with have 95 octane minimum. It is hard to find lower than 93 octane here anyway.

So I need to flush the engine with carb/fuel injector cleaner after changing the seals as I understand. Let's see what happens after that.
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Old 05-16-2009, 12:17 AM   #40
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Re: Why does my engine knock??

I would suggest datalogging your car. You'll be able to tell where the spark knock occurs (engine load vs. RPMs) and you'll also be able to see the BLM and the INT so you can tell what the computer is doing with the fuel. I went through some headache with my car trying to figure all this out and it took quite a bit of datalogging and learning what all the numbers meant to figure out what the problem was. Replacing parts and guessing at the problem didn't help much. Good luck.
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Old 05-18-2009, 09:38 PM   #41
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Re: Why does my engine knock??

Not sure if you've got it fixed already or not, but have you checked the Ignition Module? I had detonation that would only happen when the engine was at N.O.T. and under heavy load. Turned out to be the module. Not sure if it had got to hot a few to many times, but it's an easy test at the parts store. I had to run about -3* just to get the detonation to go away. So I guess you could say that the module decided to kick in extra timing for S&G.
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