I guess I should give a little background first. I finished rebuilding my engine a few months ago and got it running fine. I'm running a 3200 stall with a stock trans. The motor has been running for almost a month now with no problems, until now. here's what I'm running into. I installed a set of long tubes about 3 weeks ago and replaced the O2 sensors while I was at it. I drove it around for 2 days with open headers. I then installed a y-pipe and took it to the track. I made 4-5 passes at the track again with no problems. I then drove around for a while and about an hour after making my last pass, I started to get a hesitation. In any gear, it would accelerate normally till about 2500 rpm and then bog down really badly. (I don't mean like "oh it doesn't feel so powerful", I mean it has a very hard time accelerating) If I hold the throttle constant the rpms won't increase unless I really lean into the throttle. At about 3000rpm it suddenly catches and drives like normal again.

I've done a little bit of testing and have figured that this problem only occurs after the car has warmed up and even then it is intermittent. Also if I brake stall the car it will bog immediately too.


I've done alot of reading and so far I can't find anyone else that has had the same peoblem. I've thought about a slipping tranny or bad opti, but it lacks symptoms like a rough idle or constant slipping to really make those theories solid. Please help me out and offer any advice.

 

First off, has the car been tuned? Second, do you have a laptop and an aldl cable that you could log the car with? If you could do this, and post up the log, it would be much more helpful.

 

yes the car is currently running a tuned PCM from MadZ28.com.

I have just ordered a cable and it should be here tuesday or wedsenday. As soon as it arrives I'll log a few runs.

 

I also just discovered the problem goes away if the car is left in open loop mode. I replaced the o2 sensors to see if that corrects it. It seemed to fix the problem after about 20 minutes of test driving, then it bogged once more after I stopped for gas, then it went another 20 minutes with no problems before I parked it......so I'm not sure what any of that means, but I'm sure it will help in someway.

 

I would have suggested unplugging the O2's to check for good operation in open loop, but I would say that it is a sensor or something that is causing it to do this. That's why I suggested logging the car so we can check it out for you. That probably is your best bet.

 

Check for a broken wire to the O2 or a loose pin in the connector.