I've been having this problem for last few months. I only get pinging when my engine has warmed up, and this has been getting worse now that it's summertime. I ping almost constantly when I am trying to accelerate slowly, (say to save gas mileage) and once I reach second gear (almost never pings in first no matter how fast I accelerate), I can get some pinging. I get the most pinging when I am crusing along in 2nd or 3rd, and then I give it some gas, but not quite enough for it to downshift, then I can get crazy pinging... I'm talking like 2000-3000rpms here. If I floor it I get no problems, unless I've been idling for a while.

This engine was rebuilt one year ago, and has about 10k on it. Sparkplugs are one year old as well. I pulled several of them, and they have a slightly red look, with dry-looking powdery white look to them.

Checked the timing, and it is exactly 10* with the EST turned off. With it on, I read something like 27* while the car is NOT warmed up, and it slowly lowers. I figure this is because the timing is not readible when this is plugged in.

I also smell a great deal of unburnt fuel from the engine compartment, and when the fan comes on you get a face-load of delicious fuel fumes. This confuses me, because I thought if you smelled unburnt fuel, that your plugs were fouled and had carbon/oil etc on them.

I wonder if this could be a computer problem? I am pretty sure that the distributer was replaced, and I know the wires were replaced for sure in the rebuild. The other reasons I think it could be a computer problem is because sometimes when I floor it, my speedometer stays at zero for a couple of seconds, then jumps back up to the correct reading (well correct is 15% slow because of some gearing problem)... it did this before then I replaced the TPS... that fixed that, so now I think its something else. Also my a/c no longer turns on the electric fan, and I am aware that the computer controls this as well.

Things I've replaced in the last two years. TPS, both oxygen sensors, fuel filter, many air filters, 3.1 longblock, plugs, wires, EGR, and probably a few others.

The ping I speak of is basically an octane knock, because it gets a lot better with higher octane fuel. Right now I am using 89, because at 87 the car is almost undrivable... But it will still ping about 15% less with 93, which seems absurd with a stock buildup capable of running without detonation on 89 regular unleaded.

My wallet is hurting here guys, I fill up 3 times a week, and I get 15.5 mpg in the city. I delivery on the weekend, and I idle around quite a bit, but do do millions of other drivers who don't have pinging problems.

The first thought on my mind was to replace the plugs, but should I go hotter or colder? I don't think I should have to go non-stock if the ignition is working correctly..

Sorry for the long post, but I've been trying to fix this for a while.
Thanks,
Steven (1990 3.1 Firebird MPFI)

 

I'd make sure the ring on your harmonic balancer hasn't slipped. Bring #1 (front PASSENGER side cylinder) up to TDC of compression stroke (check w/phillips head screwdriver). Then look at the mark on your balancer. It should be lined up with the 0 degree mark of the timing tab. I'm wondering if your timing is super-advanced, but you "think" it's at 10 degrees b/c of the slipped balancer.

You might also have a fuel leak somewhere, or an exhaust leak. Have you put a fuel pressure gauge on it? If there's a leak somewhere, fuel pressure will drop instead of hold. An exhaust leak would do two things- it'd confuse your oxygen sensor (oxy sensor would see fresh air, and think you were running rich, so it'd lean you out), and it'd also push any gas fumes into the passenger compartment. Remember that if you run too lean, the a/f mix won't ignite properly.

 

very interesting... because I think I am developing an exhaust leak. Sounds like it's the donut at the ypipe connection again... I wonder if that's something that the rebuilder should have covered under the warranty?

Also, it's been doing this for a while, even before I seemed to have this exhaust leak...

Is there something that could have been built wrong internally that could cause the engine to ping? To my knowledge, it seems that the only thing that can cause detonation are the sparkplugs igniting the fuel early because they are too hot... or they are too cold, and carbon deposits have built up, which ignite the fuel early too... other than that, all I can think of is that the computer is broken, or getting the wrong signal.

Do you know if you can hook up a mechanic's computer reader to my car, and read the o2 sensor and all that? I can make my car ping while its in gear and I push on the brake---powerbraking...

so the leak would have to be before the o2 sensors... hrm, I guess I'll have the muffler place take a look see and see what they see... its funny, ever since I had the engine rebuilt, I could always hear what sounded like a bottom-end noise... but if it had been, the engine would have been destroyed by now. The mechanic (which I have taken it back about a dozen times to for problems from leaking rear mains, to leaking exhaust manifold gasket, to destroyed tranny mount...along with engine mounts--all things he should have seen when he did the rebuild...) assured me that it was not a bottom end noise... also another shop has told me it was an exhaust noise... but when I go to the exhaust shop, they tell me its a bottom end noise.

I wonder why the shop can never find the leak there, what method do they use?

Also, what are the chances the computer itself is bunk? Or is it a really good chance a sensor is reading wrong?

 

Interesting... when I pull off the EST connector, I NEVER ping... I have determined it is not possible on my car with that disconnected. I lose a lot of low-end speed because the timing is not advanced enough, but when I reach about 2500-3000rpm, it picks up just the same as before, but get this... with out pinging...! It's weird that I can accelerate much faster without pining with the EST off, than if I just baby the accelerator with it plugged in... It's like its SUPER-adancing the timing automatically... bah computers! I should have just taken my brothers 350 carbbed that he was gonna give me for free... but damnit I wanted a computer for some reason... stupid! stupid! stupid!


Also on the point of the o2 sensor causing it to ping because the mixture is too lean... shouldn't the knock sensor stop pinging no matter what before you can even audibly hear it?

Thanks,
Steven

 

Well first....it might be possible but not exactly practical. Factory O2s are...well...crappy. Theyre not designed to give a specific reading. They basically operate under 3 positions: Rich, lean, or stoich. They don't know HOW rich, or HOW lean you are...just that you ARE rich or lean. To really get a good readout from an O2, it has to be wideband, which is pricey. Factory O2's act very peculiar when hooked up to a gauge. At idle, they won't really read at all. Most I've seen will zip from lean, to rich, and back again.

So basically....your motor pings under normal electronic advance. Base advance, no ping. 93 octane does no good. Plugs are good. Sounds like you're running lean to me as was suggested earlier. Powdery white plugs, if you're talking about the insulator, that sounds towards the lean side. But there are other explanations too, like incorrect heat range..or I believe there's even a type of carbon buildup that's white instead of the normal black. They should be a medium-tan color though...and I don't see why factory replacement plugs wouldnt be the proper range for your rebuilt motor.

I'd throw a fuel gauge on it and look into your fuel system, see if the pressure is good. I believe you're shooting for around 40 psi with vacuum, roughly. Maybe a liiiitle bit less...but I'd say no less than 35 is acceptable. Then pull the vacuum line to the regulator off, plug it with your finger, and see what the pressure does. Pressure should shoot up another 5 psi or so as soon as you remove the vacuum from the regulator. Is your O2 sensor old? For $20, it might be worth a shot.

How's it idle? Smooth? Last thing I can think of.....have you checked for vacuum leaks? A vacuum leak will create a lean condition because the engine is getting unmetered air that leans the mixture out.

As far as knock sensor goes....I'm in the dark there.

 

huh tomP I'm confused

if the o2 sees fresh air and pushes the exhuast out before it hits the o2 it would think it is running rich?

thought the o2 would think lean if it saw more air thereby making it run richer


eh I'm confused tomp

 

Yeah, Tom... I think you got that backwards.. O2 sensor sees fresh air and thinks you're lean

 

02 sensor isn't much more than a year and a half old...

so if the fuel pressure is low, how does that cause pinging? is the engine trying to burn more fuel than it actually has, and it doesn't realize it?

I'll check for vacuum leaks tomorrow... is the best way still to spray starter fluid and see if the engine speeds up? I haven't had to do this on a computer-controlled car ever.

 

Well, the engine is going to always want the same amount of fuel as long as other things aren't modified...so if you're not getting that amount of fuel, it IS going to run lean. There's nothing you can do about that...you can't tell the ignition system to spark just a little bit weaker, or tell the engine not to pull in quite so much air. If the fuel pressure is low, that means with each injector firing, it's not firing at the normal pressure, so less fuel gets delivered. Imagine turning on two faucets, at full flow, and then at a trickle. If they're both on for, let's say, half a second, which one do you think will let out more water? So when the motor goes lean......it's going to start damaging things, and also knocking. Not sure exactly *why* it will knock, but I'm pretty sure it will.

As far as vacuum leaks, I'd do a visual inspection first... And if you can't nail it with that, then try the starter fluid or TB cleaner.

 

yeah, I looked it over a while ago, couldn't see any visual leaks, so I'm gonna get out the starting fluid tomorrow. If the sparkplugs are dry white-and partially red looking, does that mean that they can be causing this pinging too, or are they just a result of the pinging?

 

Uhhhm....I'd kinda say it could be either. For how cheap spark plugs are....I'd say buy a tester set. Just get some cheap-***, standard issue copper plugs from Autozone or whereever, slap them in, and see if anything changes. For MAYBE $2 a plug....it might just be worth the chance. If not...well....save em for your next tuneup.

 

good idea

 

haven't had much time to do anything, is because my damned brakes went out while I was driving.... that sucked...

 

I am still having pinging problems, even though I have changed my spark plugs.... does anyone know if the fuel filter can cause the car to ping? before all it did was hesitate when the filter was old...

I'm wondering if there is any connection between these problems:
1. Excessive pinging under even light acceleration (which goes away entirely with the EST connector removed)
2. Speedometer sometimes sits at zero for a minute then bounces back up to the "right" speed.. (right is still wrong, because I think a gear in the tranny is wrong)
3. RPM's drop VERY low when I stop fast, and sometimes the car dies... normally it just drops to like 300, then bounces back up to 1000... wonder if that's an air leak or something.... it happens when I'm going like 30, then I stop kinda quick.. not emergency braking or anything super harsh....

can the speedometer problem indicate that the speed sensor is bad, and is causing the timing to change enough to cause pinging?

Thanks,

Steven

 

As Tom hinted above in his first post, you have a timing problem. The car is timed way too advanced. You are either,1) timing it wrong yourself, or 2) have a faulty timing mark. I would not drive the car anymore with it like that! predetonation is ruining your motor. I would strongly suggest you take it to a professional if you can't get it right by now.

If you wnat to try it again yourself, just simply back down the advance about 5* from what its at then try again and see what you have. Are you also playing with the idle adjustment screw to raise or lower your idle? If you have, you shouldn't need to ever touch this unless the TB is aged and worn- then it would adjust very very slightly.

 

Of course a plugged fuel filter can cause pinging. When you have a lean condition, the cylinder temperature shoots up and causes pre-ignition.

Also, is your EGR valve working?

Also, you said you smell fuel under the hood.....you might have to pull the upper plenum and check for leaks from the injector o-rings. If you're leaking fuel, this will easily cause a lean condition and possible pinging.

Quote:

3. RPM's drop VERY low when I stop fast, and sometimes the car dies... normally it just drops to like 300, then bounces back up to 1000... wonder if that's an air leak or something.... it happens when I'm going like 30, then I stop kinda quick.. not emergency braking or anything super harsh....

Sounds lean. Fuel pressure is lowest on deceleration due to engine vacuum being at its highest. Put a fuel pressure gauge on it and check for a rest pressure drop.

 

Sounds to me like you're running too lean, with too much timing.

Do this -

Change your fuel filter. FF504 - $5-6 from Autozone.

Check your fuel pressure. You should have about 40psi.

If those check out good, then turn around, and VERIFY your balancer. Bring your #1 cylinder (front PASSANGER side) to TDC, (just rotate it slightly, using a screwdriver to 'feel' when the piston is all the way up) then take a look at where the mark is. It should be at 0. If it's significantly off, then you need a new balancer.

Also, do you have vacuum going to the fuel pressure regulator?

 

A couple of thing will cause pinging all have been mentioned above. I'd say it more of a timing issue. Just for the heck of it set your timing to 6* and see what happens, if it still pings set it to 0* and see what happens. Be the ballancer has slipped like Tom mentioned and your getting an false readings. BTW with the EST disconnected timing is locked at 0*- 3*

 

I would set base to 12-13*

And see.

 

VERIFY the balancer, first, BEFORE trying to do ANYTHING with the timing.

Timing's not locked to 0-3 with EST disconnected... it's set at whatever you have the base timing at (10, 12, 37, etc)

 

Are you running the correct plugs in the car? I went for a set at Autozone and put them in when the car detonated real bad and destroyed 3 of the plugs. I went to the NAPA and got another set and their number was different than the ones that Autozone gave me, the ones that Autozone gave me was a hotter plug than the NAPA ones (which turned out to be the right ones). Also I would suggest in checking the balancer as well. And are you sure that the base timing is supposed to be at 10*? I know my 2.8 is supposed to be at 9* but one degree shouldn't make that much of a difference.

 

I believe I have autolite 24's in there... or the delco version... the plugs aren't the issue because I changed them and I noticed no difference, they were a different brand before...

Does anyone know what the timing should look like with the est connected? the timing is dead on when I have it pulled off... but if I remember correctly, it goes off the scale when I rev the motor at all... I think it went beyond 25.... didn't ping though because the car was in neutral.... that's why I thought that you can't tell what's going on when it's connected.

I just got a new filter and I'll have to put that in, I hope that's the problem, but does anyone know if there is any correlation to the speedometer flaking out like that and pinging? I remember a long time ago, my speedometer fell to zero for like 5 minutes while I was going like 60, and all the sudden my car started running like crap... no power, then it jumped back up to 60, and I got it all back... just wondering what all happens with the speedometer and timing... also how do our cars get speedometer readings? is it a sensor inside the tranny, or is there a sensor outside that reads a magnet or whatnot on the tailshaft?

It's weird though my car doesn't really ping until I start delivering chinese food on the weekends, I assume since its running quite a bit and never has a chance to cool down... but the water temp doesn't seem to be the best way to tell if its gonna ping. Sometimes it will ping at 230f or 220, or sometimes not even at 230....

The thing is my fuel filter is only 1 year old, and when it was bad before I never had a problem with pinging... this is a relatively new problem, started about 4-6 month after getting my engine rebuilt... I wonder if any of the sensors could be causing this problem and just aren't throwing codes?

One last thing... are you supposed to hear a hissing sound from the driver's side front fender? I can't remember if the vacumm canister is located there, and/or if it makes noise when you turn off the car, but maybe I have a leak right there... one more fun thing to check into

 

There ain't no way I could do this.... I'd be like the drug deal who did his entire supply himself without any profit.

Did You try retarding the timing 5* from the current reading you have? If not, then no one ccan help you any further. Don't try and reset it to the balancer marks, Just move it down 5* from where you are and drive it to see how it reacts.

 

everything you keep describing sounds like spark knock. one thing that is possible is carbon build up. since your car does a lot of idling, it can build up fast. after working at a dodge dealership w/ the magnum engines and spark knock, ive learned a bit here and there, lol. also make sure your spark plug wires arent all twisted around eachother and crossing a whole lot.

 

all i know about this situation is from my own experience. I dropped in a rebuilt 2.8 from recon and got in running in about a week. Drove it for a week and had a pinging tried everything to my knowledge to fix it but i have to admit my knowledge is limited, so i took it to the shop and they went over all the usualls but finally told me the valves needed to be adjusted. they were saying that if the valves were too tight they would stick open? dumping more fuel into the engine than normal causing it to run rough and ping untill higher into the RPM band. just thought id share my

 

that is interesting... I wonder how much that shops ended up charging you when you got through their usual "screw the customer in the ***" procedure....?

I will try retarding the timing 5 degrees anyhow, because like you guys said maybe the timing mark slipped... even though I would assume this would have been part of a complete longblock... I guess it's possible whoever rebuilt it just screwed something up in that regard... but as it is now.. when it DOESN'T ping, I still don't have all that great of performance... not even as good as when I got the car with its 110,000 mile motor in it... very suspicious...

does a longblock not come with an intake, or lifters or any of that good stuff? I wonder how screwed I got by this shop... haha who by the way told me that he couldn't hear a ping or knock at all, he said he heard some transmission noise and not to worry about it.. he said it was because I was "trying to keep up with the big boys"... I said... look man, this thing pings WORSE when I accelerate slowly... so what the hell are you talking about...? He denid pinging as I let him drive my car (he drove it as slow as humanly possible, so that it wouldn't ping... but it did!)... I hate people like him, but I still don't know that something he did engine-wise could have any affect, since he didn't really rebuild anything apparently.

 

a longblock comes USUALLY with block, crank, pistons, rods, cam, heads. usually oil pan, some have lifters, rockers and pushrods, some do not. ive seen them both ways.

there is no intake, valve covers, timing chain cover, or any accessories.

 

You must burn your EPROM changing the Tº for fan ON near to your thermostat temperature.

My thermostat open @ 88ºC (190 ºF) and my fan 1 start running @ 93ºC (ON) and finish @ 89ºC (OFF). This condition controls a lot the engine temperature and knocks/pinging (coolant Tº range is 91ºC +- 2º C).

Since you use your car as a "delivery vehicle or Taxi" the air into the engine compartment is high the most time and it contribute to pinging.


(You can try other commercial use for that poor car. For instance, if you deliver sea foods from the harbor to the city, you'll use the car at the highway and pinging will go away).


Regards,

Denis V.

 

some interesting information...

My battery is not the exact fit for this car, and apparently the battery lock, or that piece of metal you bolt against the battery did not hold it right, and it moved around a little bit when I drove... this screwed up some hoses around there going to the cruise control and some other stuff...

another thing... the punks over at Travis Motors... (don't EVER go there... in austin, texas)... lied and said that they changed my water pump (because they "might as well do it while we have the engine out... and its cheap!")... well they didn't do jack crap... apparently.. cuz I got out of my car on a delivery last saturday night, and smelled antifreeze! oh crap that always means something bad happened... hrm weird my temps are okay... crap I could have a leak and already the sensor was reading bad temps...

well the fan came on and the temps came back down... and I couldn't stay where I was at, so I drove it back home with the heater on... I found what I thought was a magical hole in my water pump, but later figured out its called a "weap hole"... something that happens when the bearings go out on your water pump to keep pressure from screwing up things...

bah, so I went out and got a lifetime warranty pump for $35 at advanced auto parts (no core charge,) and started looking at all the wrenches and bits and sockets and all that fun stuff... well after about... oh 6 different trips... and 6 different stores... I finally found all the little torx bits and metric tools I needed... then I broke my 3/8" -> 1/4" adapter... that was fun, I guess I don't know my own strength.

Anyways, this sure wasn't a straight-forward removal... I was thinking more like a 20 minute job here... I sure as hell didn't expect all this... it turns out you have to take off, not only the bolts that hold the power steering pump bracket to the waterpump/engine... you also have to undo the lower/upper A/C brackets... because somehow, (it almost seemed impossible...,) they share some bolts I guess... dunno... well that took forever to figure out... then that was that... this could have taken... hrm, like 20 minutes if I had only known that... damn that haynes manual for not having the friggin removal instructions for the water pump! it was more vague than if I had written it myself...

oh well... lesson learned...

someone should make a tech article about this, and if there is... I sure don't know how to find it...

hopefully I can find all these vacuum leaks... I will probably go buy a billion feet of hose and take a week off work... maybe buy a back brace while I'm at it cuz it sure starts to hurt after you're leaning over that far! I like working on my f-100 cuz I can stand inside the engine bay and work on the little 3.8 in there...