Just like the title! Last summer I put the my headers on and never got it tuned and I still haven't removed the EGR either. Well 1 day I drove down a dirt road and hit a few big pot holes, it ran fine till I got home. The car sat for a couple of days and when I started it up it idled rough. Now it idles smooth and soon as I hit the gas it hesitates really bad, and if I try to give it half throttle it shakes the whole front end of the car. It threw about 5 codes before, it was map sensor, o2's, EGR, TPS, and after I changed the o2's all of them went away. And lately after alot of start attempts i threw a code 26 QUAD DRIVER MODULE 1 error, I scanned it for a couple of minutes and then it went away and has not came back!!

So far I have changed the plugs, wires, o2's, ICM and the opti was changed last summer. All the wires are ran right also. The car is running extremely RICH. I am really frustrated. SORRY ABOUT THE HUGE STORY! Any help would be GREAT. Thanks in Advance.

 

I have similar problems. Here is what I have done, maybe you can see if something here makes sense to you to check:

-plugs
-wires
-opti
-ICM
-coil
-o2 sensors
-PCV valve
-fuel pressure check OK
-vacuum check OK
-unplugged MAF ran car, still the same


Also, when my car stumbles it is pulling alot of retard, around 6 degrees or so. I think this is related, I tried disabling the knock sensor no luck.


What i'm doing tomorrow is putting in a new computer with knock retard disabled and I blocked off the EGR system, see if that helps.

What else I have to do is check all the sensors, I have an OBDII there are no codes thrown however, kinda stumpin me to. If i get my problem fixed I'll let u know what it turns out to be. Also maybe I would have to check for a clogged cat, but i doubt it becuase it runs great at WOT.

My problem is mostly part throttle stumblin.

Maybe someone else can chime in here, what are the list of sensors that can cause part throttle stumblin?? Can it be TPS, IAT, etc..... Just a list to check

Brian

 

I remember someone told me that if I did not get my car tuned after my mods that it would start acting the way that it is. I don't know if that is the truth or not. My car also blows back out the TB when I try to start it, but that only happens after a few tries! So I don't know if the MAP sensor has anything to do with it.

 

I wouldn't rule out the opti, even though it's new. You have a '93, so with the vent holes in the bottom it is conceivable that going through those pot hole (were they filled with water?) splashed water right up in there. And I put a cam and heads on my 94 without a tune and it ran just fine. I just put headers on and it's been running awful since then, running as if the opti is bad even though everything was fine before the header install. But I was convinced by some knowledgable people that the problem was that I didn't have a tune. So I got a tune from PCM4less and it runs the same. I am betting it's the opti.

 

i am having the same problem. i did new plugs and put my headers in and it has been running relly rough and much slower than usual. the code i threw was a multiple misfire code. i think i need some new wires and that should fix the problem, correct my if im wrong. also if i get a dyno tune or any tune will it help it run more efficient. any help would be great

 

As far as the pot holes go it was a little damp outside but no big puddles or anything. I was about an 1/2 hour away from home when it happened and it ran fine till I got home. Ever since I put the headers on it didn't run all that good and didn't make me any faster. I am really having problems with the 6 cylinder, it will throw spark while it idles and then sometimes it will cut out and not throw any. And then other times it will be fine till I give it about 1/4 throttle then the spark will be erratic. That's while I was using a timing light.

 

Are your headers coated because if they are you might want to change them. The coating melts off and coats the o2's and causes misfires. (That might help you out)

 

Change your O2s as mentioned...

And check, recheck, and TRIPLE check to make sure you aren't burning any plug wires. From what you describe, I'd put my money on burned plug wires.

 

Still confused!

I just replaced my MAP sensor cause the old one was nasty and had alot of crud on the vacuum port. After doing so the car the car started up fine and seem to be running fine but the motor was cold. I drove it around for a few minutes and it seemed to be running better than it was but still hesitating and after it got hot it started doing it real bad again. I was wondering if I should change the plugs again cause they were covered in carbon deposits all over the whole tip of the plug? And if they are like that would the o2's be the same way? I am getting spark on all 8 cylinders now but the #6 still has an erratic spark in the mid RPM range. I have not changed the coil yet! thanks in advance.

 

It seems to be a definite fact that coated headers will ruin the O2's. But I wouldn't expect this to happen until after 100 or so miles of driving. There was a GM bulletin that clear RTV silicone will ruin O2's and I don't doubt it, but I put a ton of that stuff on to seal my intake and it didn't ruin the O2's after 1000 plus miles, at least not so I could tell. I've read that after 200 miles or so, what's going to burn off the headers and foul the O2's is off and it's safe to put new ones on. As for the tune, I personally don't think a dyno tune is worth the $500 or so that I hear they cost. You can get an unlimited e-mail tune from PCM4less or Ion for $200 (like 90 for the tune order and 90 for the cable you need to hook up to your laptop and the car.)

DARKNIGHT93, this sounds exactly like what an opti will do when the cap and/or rotor start to go bad. Some of the other things you said though, such as indicate that the problem is something else. I can't see an opti working fine when the engine is cold but then acting up when it gets hot. But still, I would NOT rule out that freiking optipieceofcrapspark. I would literally bet $1000 that the problem with my car is the cap and rotor on the opti and I'm replacing them as soon as I can, but once or twice in the past month since it's been driving poorly, it will run smooth and will really pull when I hit it, no misses. But then within half an hour it'll run just as poorly as before. I can't explain this, but I would still bet $1000 that my problem is the cap and rotor, and I would bet maybe $50 that that's your problem.

 

I have this same problem. I threw a multiple misfire code as well, could I take the O2's out and see if they are fouled? I dont' want to buy new O2 sensors if I don't need them.