My ignition timing is bouncing around at idle. The idle is erratic and has been for some time. I remember some time ago that it got so rough the engine quit and set the ESC code. It has since smoothed out a bit but is still too rough. The cap, rotor, wires, and plugs have been recently changed, as well as the ESC module (that was done some time ago.) I've pretty much ruled out vacuum leaks, as it seems that every symptom points to something electrical. Could a "burned" knock sensor wire (the blue one) be the culprit? Here's the big one: Has anyone ever experienced an electrical problem that has caused a hesitation on "tip in?" Has anyone ever experienced these problems before? If so, any pointers would be greatly appreciated. Thanks to all who respond.

 

Guy, I have had the same problem for a while, I changed all sorts of sensors, egr valve, pcv, you name it I changed it. The car wasn't throwing any codes and I ran it on my buddies scanner and everything looked perfect. I just took it to GM and they told me that I have 5 out of 8 bad injectors. Of course they said that may not be the only problem. I'm going to replace them and I'll let you know what happens.

 

I experienced a similar problem. I chased the slight miss at idle for almost two seasons. I finally determined that the injectors that had been "cleaned" by one of those on-car services needed to be cleaned for real. They got pulled, sent off to cruzinperformance, and my problem was solved.

Your timing can vary at idle with the ECS enabled. If the timing varies with the ESC in bypass mode, the distributor may be worn.

 

By the way I put a 5.7 out of a 90 camaro, so we have the same crappy injectors. Read up on them in the search, you'll see.
As someone said, it's not if they'll go, its when.

 

Ive had this happen with a lean condition or a miss. The timing is probably a byproduct of some other problem. On mine everything was new and tight but the engine speed was so erratic from a lean condition that it was causing the timing to scatter even though a constant 20 degrees was specified.

 

Also, some of the computers have derivative idle SA control. if yours has it, the timing will fly all over the place as the computer tries to control the engine speed.

 

this is a problem that can also happen when a cam is walking.

after you check out the other things try pulling of the timing chain cover and inspect how far the cam button is walking, is should walk a little, like a couple thousands, but nothing much, if its moving like a 1/8 inch or so, you will need to aplly pressure on the front of the cam, or at least a stop so it doesnt walk so far. i dont remember if the stock water pump has the ability to do that, but the edelbrock water pumps have a provision that allows you to run a bolt to press on the timing cover and reduce the abount of walk the cam has.

check the inside of the timing cover and see if you have scrapes on the inside of the cover.

Might help...

~Nick~

 

First, I'd like to thank all of you who threw in your opinions and experiences. It really does help. I didn't want to bore everyone with the details of my recent build up, so as usual, I didn't include all of the things that I did to the car. I should have and I apologize.

I just finished a cam (Crane .429/.452, 116 L/S, 204/214), heads (World S/R Torquer 305), Timing set (Cloyes true roller), Injectors (Ford Motorsports 24#), and chip (to tie everything together) swap (whew!!). I'm in the "tuning" stage, and needless to say, some old gremlins have reared their ugly heads again.

Fuel pressure appears to be steady at 44psi/idle. That may be too low as Crane recommends an AFPR (I have one) for this swap, and I'm running the same pressure as I was running with the 19 pounders. The flow constants in the chip must be correct, because there's no black smoke, even outside of closed loop. The timing appears to be steady with the ESC bypassed, it just idles like crap in that mode. The car has its original roller cam block, and there didn't appear to be any weird cam or distributor wear when I yanked the stock cam.

It's just so strange....when I put the timing gun on the balancer (with the mark high-lighted with white out) and goose the throttle by hand, it's as if the timing "light" disappears for a split second after tip in and then it revs as normal. This can be frustrating as when I was watching fuel pressure under the exact same conditions, it dipped briefly at the same time (tip in) and then went back to normal. Putting two and two together, it becomes next to impossible to figure out what is the "cause" and what is the "effect." I guess I'll just have to inspect the four wires that go into the ESC control module, and see if any are damaged. Years of fighting with this problem intermittently have convinced me that this problem is electrical in nature so I'll just have to keep on fighting. With all of these items on the car, along with my Vortech, this puppy should be flyin', but it's not and I'm going nuts. The only thing keeping me sane the willingness of all of you to share your thoughts and experiences. It is appreciated and I thank you all for any ideas you may have.

 

try using a different timing light as well, i have found that older timing lights can skip around when used with certain ignition systems.

just a thought

~Nick~

 

Actually, it is a relatively new timing light, but I have to admit, that is an idea I haven't heard before. I may just try another light to see if that clears anything up. I also once heard that in order for the engine management system to function at its "peak," the battery must be in excellent condition. I think that a load test may be in order as the battery is nearly four years old. Thanks for your insight.

 

Check your pickup coil wires inside the distributor. Check whole wire, not just what you see. I am betting 80% that might be your problem. If not than replace your cables and make sure you get some good cables. These problemd usually come up after cap and rotor replacement.

 

Is that the item that surrounds the distributor shaft? I believe that it has 2 wires that plug into the module if I'm not mistaken. By the way, do I have to pull out the distributor to change it? It appears that I'd have to punchout the roll pin that holds in the gear and slide out the shaft from the bottom, but that's just a guess. Thanks

 

check it before you replace it. The wires tend to get really brittle under there causing many weird problems.

For replacement the whole distributor need to be taken apart. But make sure you check you wires first. Don't just go replacing yet. Cuz the coil is a dealer item, and they don't return electrical stuff. They are full of ****t.

 

[B]

Replaced my stock distributor with a new MSD, and my timing is dead on now. No more bouncing.

 

If it threw a code 42 then you may also want to check the connections and the ground path through the dist. base to make sure theyre good. The timing light momentarily cutting out points to the dist. dropping spark. A faulty coil will also cause missfiring.

 

My timing is bouncing with the computer (ECS) enabled. When it is bypassed, it stays at 6 or 7 degrees (steady), so as per Vader's comment, I don't think my distributor is worn. Dimented24x7's comment about a worn coil is well taken. I have a new one, but haven't replaced it yet. That's next. I've had it lying around too long not to use it. The pickup coil, according to CSKAuto (Kragen here in California) is a regular stock item. I hope it isn't a dealer item. That would be a royal pain. These are basically the last items left in the "chain" of ignition pieces that have not been replaced relatively recently, so I'll probably get around to these things soon. An MSD distributor would be really great, but there's simply no room in the budget for it right now. Hopefully, that won't be necessary. As always, thanks for all the input.

 

If it is rock-steady with the EST bypassed, try to dummy out the KS with a resistor and see if it remains steady with the EST active.

 

Thanks, Vader. Please forgive my ignorance, but I'm not sure what you're referring to with the term "KS." From what I gather, there is a place in the "chain" of ignition components where a resistor can be placed to mock up some condition within the system. This is something new to me. Please elaborate. Also, I have a kilovolt meter that I got on sale years ago. I may just test the plug wires (new) and the coil wire in run to see exactly where the spark is "dropping" if indeed it is.

 

KS = Knock Sensor

 

I had the same problem on mine. I had a horrible idle with the esc plugged in and once I would unplug it everything would get better for a while. After chasing everything I could think of I took it to a friend for a fresh look. He found a worn dist gear, replaced that, found a grounded wire to the O2, replaced that (as the car never went into closed loop) with a heated O2 and bam, the car just purrs now. I would check some of those just to be sure the dist gear is only about 30 bucks and easy to change.

 

Tony,

That sounds exactly like my problem. Would be really erratic with the est plugged in but in bypass it would be rock steady. The cause was an improperly calibrated maf that read low at low airflows. In bypass, the IAC would open and the engine would move enough air to get maf readings that where more in line with what the airflow actually was. This would inprove teh AFRs and steady the idle. MAF/injectors are probably not your problem but its another possibility to keep in mind.

As for the KS, its usually ignored at idle because on startup the starter can cause teh knock counter to roll over several times. And also you wouldnt want to have timing pulled at idle if theres a KS failure. None the less, though, its probably not a bad idea to try and bypass it, just to eliminate that possibility.

 

I actually disconnected the knock sensor wire completely from the sensor itself just to see if it made any difference at all, this last weekend. I was thinking exactly the same thing. As it turned out, it really didn't do anything, but it was definitely worth a try.

I recently checked out my distributor gear, another good idea, but as it turns out, it's fine too. It has a very conservative wear pattern: nothing out of the ordinary for the car's 83,000 miles. I know that the module grounds through the base of the distributor, however, and that definitely needs to be cleaned at least. It may not help, but it couldn't hurt.

The mass airflow sensor.....where to begin. I recently replaced mine when it went bad. It is brand new, not a reman. unit. That's one mistake I won't make again. My last refurbished one went out in a week. That really sucked.

I was recently told by one of the techs at TPIS that my bog and screwy timing could be caused by a "slow" oxygen sensor. The car throws no codes, but that could just mean that the computer isn't seeing any voltage numbers that are out of the "normal range." It's no guarantee that the number is correct, of course. The wire to it has "split loom" that is melted. It's possible that the wire itself is melted, damaged, or worse. I'm thinking about Bosch 13077, and fixing the wiring. The real answer here lies in doing some datalogging. I don't have a cable yet. That is coming next. I'd really like to see what the heck is going on in the ECM in real time. I bet it's a real eye opener.

My kilovolt indicator might provide additional clues. If the distributor is indeed dropping spark, the way I see it, that is happening because something upstream of it is telling it to (duh). The list of components between the ignition coil and the ignition switch isn't very long, so hopefully with some determination, I'll finally make some headway.

Another point worth mentioning is the health of the battery. Mine is four years old, and if memory serves, the last time this problem was this bad, a new battery helped quite a bit. Thanks again, everyone. As always, it helps.

 

It could be the clearance on the distributor shaft (between shim and gear). Every .010" gives you a degree variation in timing. I got mine down to .0025", after I jury-rigged it with a re-finished washer. I had .095" before.

 

I wouldn't go any less than .010" clearance, the aluminum housing and steel shaft expand at different rates.

 

I ahve a single wire o2 with headers and for the first 10 minutes or so its sluggish. I havnt experienced any erratic idles, but it does cause a rolling surge as the computer tried to get the desired output out of the O2. To be sure, you can just disconnect the O2 sensor and the computer will be forced out of closed loop when the O2 volts remains at .450 (also will set an SES and a code 13). If its markedly better, then youve found your problem. Id disregard TPIS' comments, though, if this also happens at all times and not just when the engine is warm.

 

After troubleshooting an earlier idle problem and making it better for about a month (replaced TPS, IAC, cap, rotor, plugs) it seems my problem has come back. I decided to again make sure my timing was right so I disconnected the EST connector by the blower motor and checked the timing. The timing was dead on (6BTDC for L98) solid and with the EST connector disconnected the car ran perfect. Plugged the EST connector back together and it runs like crap, idles bad. I've done a few searches and looked over a wiring schematic but I'm still kind of confused as to what components are related to this type of problem. I see athe EST as a connection between the distributor and the ECM. Is the EST built into the distributor or is it a seperate component? This post has given me some new things to test. Had no idea the Knock Sensor or the MAF could cause this. I know Vader had an earlier post on how to dummy out the knock sensor (I'll do a search) but to dimented24x7, what should the MAF readings be at idle?

 

You should see around 8 grams/sec at idle.

https://www.thirdgen.org/techbb2/sho...ight=MAF+table

Theres some info on how to test the MAF. Also be sure to visually inspect the MAF wires and make sure they are clean and free of deposits. Deposits insulate the wires, and cause the computer to underestimate the flow. If the wires are dirty and you can access them, a q-tip soaked in naphtha or some other residue free solvent cleans them well. If theyre unaccessable, then replacing it is the only other option.

The EST is made up of the ECM, and the ignition module. The ecm contructs a voltage based signal that is based of off the needed advance, and the required dwell for firing the spark coil. This voltage is fed to the module, and is what controls the timing. If there is an intermittent open circuit or noise on the line, it could cause erratic timing when the bypass connector is connected and the ecm is controlling the timing. You can check the output with a volt meter. It should be a smooth varying 0-5 volt signal. Testing for noise could be more difficult.

The other thing to be sure of is that there is a good ground path. The dist. base and engine block are the only paths to ground that the dist. and coil have. If the dist. base, hold down camp and intake are dirty or there is a faulty ground at the block, itll cause problems.

 

Thanks for the tip. I'll have to check that out.

 

Yes thank you for the information and tips. I need to check my scantool again to see what the MAF is reading. Thanks.