ignition problem...?

[1984grandnat]

Well, I've been pondering this for months now...just thought I'd see what you guys (and gals) think.

Here's the situation:
I can't run the car at WOT at this point...anything over 5 psi will result in really bad sputtering (maybe just one cylinder--hard to tell), and then it knocks and falls on it's face. I have replaced the coil pack, plugs and wires. The car has new injectors, and plenty of fuel pressure (Walbro pump, hotwire, etc, etc...set at about 40 psi static). When I add race gas, the knock disappears, but the sputtering is still there (starts at about 5 psi). The TPS seems to have a good smooth sweep, and is set as close as I can get it. I have tried several chips, and they all do the same thing. It seems to me like there is not enough spark energy to fire the plugs under boost. That was my theory when I replaced the coil pack. My next question is: does the ignition module have anything to do with spark energy? ...or is the module simply providing proper "timing"? I also question the ECM...I have had several intermittent codes being set such as "wastegate pulses not detected" (even though the solenoid is new and the connection is good), and "TPS voltage too low" or "TPS voltage too high". If I go through the trouble to set the TPS, it will be fine for a short time (couple hours), and then when it sets a code and I check it again, it will be resting at like .08 volts, instead of .42 like I set it at. Then like magic, it will go back to normal again. Obviously, this is frustrating to say the least! I have checked and double-checked all the grounds and see nothing bad here. I should also mention that I had a bad voltage regulator in my alternator over the summer (which caused my lighting to flicker, and some voltage spikes), so this is another reason that I am questioning the ECM and module.

Maybe it's time to make a few purchases from Red Regal T...?

Well, sorry about the book...maybe I need to post more often and not let all this build up so much, huh?

Thanks for any input, ...I appreciate it all!

 

[6SENSE]

Sounds like youve got it narrowed down fairly well. Process of elimination is sometimes the only method to go with, and seems to be pointing towards the ECM. Ive seen bad TPS sensors that will act like you mentioned, but under the circumstances, with the other problems popping up and the fact that you had the voltage problem I think you probably fried the ECM. You might even be able to smell it inside. Go to the junkyard and find you a spare (or two). Not a bad idea for everyone to have a spare, especially if you can still find them in the yard for cheap. I think this would be the easiest thing to try first. Ive swapped the ECM before on mine to correct a problem similar to what your describing.
As far as the sputtering the module would be my 2nd guess after hearing what youve already replaced. Make sure plugs are gapped properly also. I worked on a TR where everything was pointing towards the coil or module, until I found out he had his plugs gapped at somewhere around .065 or .070 when he swore that he gapped them at .035.

 

[1984grandnat]

Since you mentioned it...I HAVE smelled the scent of burning electronics from inside the cab...funny that the car seems to still run okay...when not under pressure!!!

I will check into a new ECM soon...do you think that the ECM has anything to do with the sputtering under boost...or is that most likely an ignition module problem?

 

[SLOW_85]

Didn't see it mentioned,how's your 02 sensor? bad 02 will cause the same sputtering under load.

 

[Turtle TR]

Maybe your Cam Sensor is out of whack. I changed out my CS and that cured my stuttering misfires and backfires that I was having. or even try readjusting your CS.

 

[1984grandnat]

I haven't changed the O2 in awhile, just kinda going on the assumption that it is okay, since my car usually sets a code when it goes bad (I know, I know...probably should change that $20 part).

I thought about the cam sensor, so I went checking on gnttype, but from the way it is described there, if the cam sensor is misadjusted, the car simply won't run...they make it sound like it will either run (if it's right), or it won't (if it's not). After reading that, I kind of gave up on the cam sensor idea (since the car starts pretty easily and runs, for the most part).

Another thing to note is that this problem has been getting progressively worse over the course of the last six months or so. When I put the new coil pack, plugs and wires on it, it seemed to get slightly better, and I thought the problem was fixed...but no.

If I adjust the FP lower, the problem gets worse. If I adjust the FP higher, the problem is still there, and I go through about a tank of gas in a couple of days. I am still stuck on this being ignition related. The more pressure that you apply to a cylinder, the more energy it takes for the plug to spark. If I have even one cylinder that isn't sparking with enough energy, the fuel in that cylinder is not going to be burned, causing the O2 sensor to read a rich condition, and then the ECM will reduce fuel to all the injectors, thereby causing a lean condition, which results in more sputtering and knock (this car is knocking at 6 psi on 93 octane!!!!).

This takes me back to my original question: Does the ignition module (or ECM for that matter) have anything to do with spark ENERGY? ...or is that all in the coil pack. We all know that the ECM doesn't know the difference between 3 psi and 23 psi boost, so I don't think the ECM cares about spark energy at all (just timing the spark and fuel so that they align properly). I would hook up the laptop and try to pull some numbers, but obviously that will do me no good in this case (if I can't get it to fire on all 6, O2s will be all over the place, and I already mentioned my TPS issues).

Thanks again for all the replies. If I am missing anything please let me know.

 

[redhotrod]

I thought about the cam sensor, so I went checking on gnttype, but from the way it is described there, if the cam sensor is misadjusted, the car simply won't run...they make it sound like it will either run (if it's right), or it won't (if it's not). After reading that, I kind of gave up on the cam sensor idea (since the car starts pretty easily and runs, for the most part).

On contrar, it does play with fueling though, you can actually adjust your cam timing from the sensor, make sure you set it at the 1.45" mark