Car is a 1986 Iroc 305 tpi.

For around a month, I've noticed that my car runs great when cold, but after it gets hot, it tends to idle rough and cut out on acceleration. After it gets moving, it was running fine. Early on, the problem would almost disappear on a cold night, but be prevalent if it was a hot day. Now, not only does it cut out and idle rough, but it surges upon heavy acceleration or WOT. It use to just be occasional, but now it happens all the time. It still seems to run pretty good when the engine or outside air is cold enough. Does anyone have any ideas? I was at first thinking fuel pump (sucks), but because of the temperature, maybe not? Could it be a MAF issue, due to the fact that warm air (less dense) effects it so bad? I'm just guessing. Any help is appreciated. I'm going to aldl cable it soon and see what I find. Also, what should I look for in particular on winaldl?

Thanks,
Dan

 

Dan, did you figure this out? I was driving the IROC-Z this week on the Hot Rod Power Tour and temps were over 100* every day. Add in some traffic and the car was running hot (230*) for extended periods. I noticed the idle sounded rough and acceleration would stumble. I also noticed that I could smell gas a lot when it was hot. Let me know if you resolved your issue. Thanks.

 

I would check your fuel tank pressure relief valve (I think that's what it was called). I think it was on the driver's side, above the rear axle. Mine was shot and I found a replacement at the junk yard for a couple dollars. I think that really helped my issue. I sold the car in January and I don't quite remember all the details.

Basically, it sounds like vapor lock, to me. The valve helps relieve pressure that builds up in the tank. Do you still have the heat shield above the muffler? 230 degrees seems pretty normal for 100 degree ambient temps, at least.

Dan