Hi guys...

Here's my problem... About a month ago, I was on my way home (about a 20 minute drive). I was at a stop light and when it turned green, I nailed it and went thru the gears. At the next light (which was about 5 miles down the road) as I'm slowing up, the engine dies. No problem, I started it right back up but it died again. It would not idle if the RPMs where under 900. If I kept the R's up, no problem... she ran smooth as ice. But as soon as the RPM's hit or dropped below 900, the it was spit, spudder and then die.

The computer was trying to keep the engine running as I could hear the IAC opening and trying to keep it idling. Usually, it would last for about 15 seconds (engine ALMOST dying and trying to stay running) then it would just die. Each time, however, I was about to restart the enigne as if nothing was wrong but as soon as it fired and come to the normal idle point, it would start it crap again.

I got it home, checked ALL the connections I could think of but still unable to stop it from acting up.

Then about 30 minutes later, the problem went away and all was fine.

For the next few days I drove it like a normal person, I never put the pedal to the floor or anything like that. Then one day I did, and the problem came back. for about an hour and then went away.

For a month this has been happening off and on so one time I decided to disconnect the ESC plug (you know the one we disconnect to check the base timing). The problem instantly went away!!! If I plugged it back in, the problem returned (when there was a problem).

I was thinking there must be an issue with the ESC module. Got a new, waited until it problem returned, pulled off the road and plugged in the new ESC module. But the problem was still there! I was in such think traffifc, that I had to disconnect the ESC plug just so I could drive it home.

So what is EXACTLY happening when we disconnect the ESC plug. I know it by-passes the ESC module for timing advance, but there's has to be something else causing this.

This is really starting to annoy me and I never know when it's gonna act up. Being an automatic and trying to keep the RPMs up at a stop light or in heavy traffic is not fun.

Help?!?!?

Thanks,
-Mike

ps: Sorry so long but wanted to give you guys as much detail as possible.

 

Anybody???

 

Somebody help this newbie!!

 

Hi
The symptoms you describe occur when the engine knocks, and it will most likely only do that when you nail the throttle. There is nothing actually faulty, that is how it works.

The fact that it was OK when you disconnected the ESC plug more or less proves the timing is too retarded at base, so when the ESC retards it further, it is too retarded to run the engine. When you rev you advance the engine and it will run.

The problem goes away after a while when the ESC releases teh timing back to normal.

However for it to knock and to falter after knocking it sounds as if the ingition timing might be retarded.

When the engine is under load the pressures in the cylinders go up and the gas can pre detonate instead of burning smoothly. That is a knock. If you have high compression or poor gas the knoc starts sooner.

High octane gas is only to stop knocking, it does nothing else and in fact provides less power per gallon than low octane in an engine that does not need high octane. You get more power from high compression engines, and that's when you have to have high octane gas for them to work without knocking.

Reset the timing and try again. If it happens again try higher octane gas. If that doesn't work then check the sensor and ESC module.

If it was a sensor fault, you would most likely get a fault light with it. My bet is the base timing is about 5 deg retarded.

 

Hmm, speaking for Nitroburn, his timing is fine. Although that was my first reaction too. I figgered it was timing.
Without the ESC connected, it's at 4*.

And I think you've got your retarded and advanced mixed up in a few places there.

Maybe Mike will chime in with a few more details or theories.

 

double post

 

NT... newbie? You're gonna get it for that remark.

As far as the timming, NT is right, the base it at 4* which is always has been since I rebuilt the engine. As I stated, I replace the ESC module but that didn't fix the problem.

As far as fuel, I ONLY run 92 or 93 octane. Period. I did try 89 once about 2 months ago and it ran like $#@^ and got a lot of knock counts from it. I'd rather run the 92 or higher octane and keep the timing at 4* rather then set it at 0* and run the cheeper gas.

Do you think it could be the ignition module or the knock sensor?

Thanks,
-Mike

 

I don't think it would be the knock sensor, only because the system shouldn't retard the ignition to to point where the engine wont run. I did have an engine retard on me once when the distributer bearing were seizing up, so it would be worth a check. Also if you trigger the symptoms by nailing the engine again you will be able to check the timing and see if it is OK. You have to nail it under load.

That isn't to say the sensor is OK. Also check it is tight and the wires are good.

As timing when the engine is faultering is an easy check, I'd do that first, also pull the ESC connector and see what happens to the timing. That would take away the guess work from that part of it.

It could be the state of tune, if it is really good at getting air at high RPM, and it looks like you have the high compression pistons the engine will probably knock at high rpm under load. But even then it shouldn't falter like are getting.

Which bit did I screw up on in the first shot, I can't see it.

 

When the ESC is connected, timing is advanced (at idle) somewhere around 20-24* (maybe more, it's off the scale and I don't have an Advanced Timing Light). When the ESC is disconnected, it's at 4*, right where I set it from the get-go.

There are times when it will act up where I do NOT do any WOT actions.

There was a time, when it was acting up and I had enough time to get the timing light hooked up. Everytime the RPM's dropped to where the enigne would die and the IAC opened up to try to keep it running (or myself operating the thottle by hand), the timing light would just die (meaning no spark what-so-ever).

So it seems that when it does this (won't idle crap), the spark is just cutting out unless the RPMs are above 900+, which at those revs, it's smooth as ice.

Wha thte heck would make the ignition just cut out like that at an idle?

 

Now that is interesting.

There are a number of possibilities here. Not all computers should have the line disconnected to set the base timing, some just need the shunt in the diagnostic connector. You have to check by model, so that needs checking. Thats a cheap check. You might be disconnecting the line when it needs to stay connected.

For an engine to advance 20 deg it is almost like the computer thinks the engine is reving at 2000 rpm, if it thinks that, it will also supply all the gas needed for 2000 rpm, and that will flood the engine. That would explain some of the symptoms.

If the module was faulty it might send too many pulses to the computer and cause the computer to advance and flood the engine.

Worn distributer bearings and a slow speed whirling of the shaft, can trigger multiple firing, but you don't seem to be seeing multiple flashes from the timing light.

It sounds though like you need to connect up to an oscilloscope to really find out whats going on.

 

Well, it's been like that (the timing advanced) from the beginning of myself owning the car. I have hooked up WinALDL a number of times (idle, normal driving, a few hard runs) and at idle it is not running rich. (Of course the RICH FLAG will flash now and then, but that's it).

Everything is showing normal (no flags, no codes being thrown) and now I can not get it to duplicate the problem (at least not at will). It will happen every once in a while, but I can't do hard or WOT run and then expect it to start it's crap again.

It's like trying to find a needle in a BIG haystack!!!

And from my understanding, the computer will advance the timing (at idle) a good fair amount and when then adjust it as the RPMs rise or fall accordingly.

As far as removing the ESC connector to set base timing, this was verified at the time I bought the car and rebuilt the engine.

 

It definately sounds like the timing is getting messed up, and also triggering too much fuel. I had this on an engine once before, in that case the distributer was worn out.

There should be almost no difference between the base timing with the wire disconnected, and with it connected at the lowest RPM.

The only reason it is disconnected when setting the timing is to make the timing completely independant of engine RPM and vacuum.

This is done to make it unnecessary to hold the RPM totally constant as the distributer is rotated to find the timing. The revs wander up and down as the timing is adjusted at that would be anoying waiting for teh revs to keep resetting.

With the old mechanical advance you had to keep the revs steady manually, also disconnect teh vacuum advance pipe.

So if you have set the base timing at 4 deg, with the wire disconnected, the base timing is likely correct. But if it advances 20+ degress, you have a definate problem there to sort out.

If it just happened, it sounds like either the ignition module, a worn distributer, maybe the MAF or any of the interconnecting wires. But it doesn't sound from the new info so much like the knock sensor, or the esc, but of course it could be anyof those or even the computer.

Are the vacuum hoses to teh MAF ok?

 

Yup... checked all the vacuum hoses, no leaks anywhere. The TBI's don't MAF, we have a MAP sensor and it seems to be functioning properly as well.

Are you sure about the timing not supposed to advanced more than the base setting at ilde with the ESC connected? I was under the impression that this action was normal.

Well, maybe I'll break down and get a new distributor (damn... there's goes part of the header $$$ )

-Mike

 

The timing will move a bit when you reconnect, but not 20 degs maybe a couple of degrees or so, then you should be able to watch it advance as the revs increase.

I wouldn't buy anything just yet, it could be as simple as a loose wire. You could spend a fortune and still not fix the problem.

It seems like the computer thinks the engine is reving way higher than it is. The only way to check what is happening is with a osciloscope. You need to check the signal to the computer and the signal from the computer which tells teh module to advance the ignition.

The scope can also check the condition of the distributer, but the cheap way is to watch how steady the timing stays when you have the strobe on. If the distributer is worn the timing will wander around a few degrees.

It sounds like you need to bite the bullet on the analysis machine. It souldn't be more than about $50. which is way cheaper than damaging the engine.

As the engine is modified you might want to put it on a rolling road and get the PROM mapped to the engine.