Ok, now my IROC is starting to really **** me off! I've driven my '86 Iroc 305 TPI probably less than 300 miles since I bought it a couple of months ago, and everything is going out on it. Computer, starter, radiator, MAF relay, exhaust broke, etc. Anyway, I get all this fixed and every time I fix something, something else goes out. Enough of my ranting and raving. Today I was driving around town and the thing just stars idling about 250 RPM at a light and then dies on me. Damn thing won't start for about 10 minutes and when it finally does, it limps about a half mile to where I get off the road. There it dies and when I start it, it will sometimes run for a minute or two and then RPMs just fall and fall while the engine sputters and pops (maybe backfiring) which leads me to believe an ignition or distributor problem. After letting it sit for an hour, it ran fine for about 5 minutes and then the same crap. After putting it on a trailer and getting it home, I hook up a fuel pressure gauge and start it up, fearing a fuel pump failure. Then it runs fine for about an hour or so and I can't see any falling fuel pressure. When I turn the key on and it primes, it is in the 40 psi range. After starting, it stays at a constant 32.5 psi for the whole hour I let it run. When I throttle up, it will pop up to 40 or so for a sec. If it was the fuel pump, wouldn't I see some sort of fluctuation or dropping pressure during that time, I even drove it and it shows no sign of falling. Previous owner said he replaced the fuel pump about a year ago, so hopefully that's not it. If it would do that again, then maybe I could troubleshoot, but it will probably only do it when I don't want it to. I don't know if I'm barking up the wrong tree or what, but now I'm scared to drive the thing anywhere. Any help?

P.S. I checked for codes and none come up.

 

Iceman,

I know it sounds strange, but I had the same type prob with my 78 T/A (carb)

It turns out that the fuel RETURN line was clogged. As long as it was idling/putting around low speed it was fine, but when I got on the road, shortly after being at speed, it would start acting like it was out of fuel. (sound familiar?)

If you pull both ends of the return line and blow it out with compressed air, the problem may go away.

Evidently, the fuel system relied on pressurizing the fuel tank to ensure good flow back up to the engine. I'm not sure how the TPI systems are, but it could be this or a clogged filter at the electric fuel pump (in the tank) Could have gotten gunked up if it sat around for awhile too.

Hope this helps,
P.

 

Have you checked anything else??? inspect the ignition system as well... any history on the car??? did it sit for a long time??? any history for general tune-up stuff??? fuel filter??? start with the basic stuff...

zroc

 

Haven't had time to check anything else yet. Car did not sit for more than 2 months. Next up is the ignition system check and I did replace the fuel filter a couple of weeks ago. Before this it did idle crappy and had codes, but me and my mechanic friend solved those probs with the new ecm, new MAT sensor, and MAF sensor power relay, but even before all that, it would run fine except idle was rough and NOTHING like this. Just trying to get some leads right now 'cause I haven't been able to reproduce the problem yet, it only happened a couple of hours ago.

 

what were the previous codes??? and what all did you do to address them???

zroc

 

We did all this about a week before this problem came up.....The car had a bad idle, check engine light. Gave code 34 (MAF sensor). When we hooked up the Snap-On Scanner, the computer wouldn't communicate with it, so a new ECM solved that. Replaced the MAF sensor, but that did nothing so we took it off and traced the problem to the MAF power relay (power was going into it, but not coming out). A new power relay solved that code, then it gave a code 32 or 33 or something, whatever the MAF Burnoff code is. That was just a problem with the relay plug being loose. Then we had a code 23 for the Manifold Air Temp. sensor and replaced that and the plug because the plug plastic had deteriorated in the sensor receptacle and wasn't making contact. That solved that code and I haven't had any since and car has been running fine. This current problem gave no codes, however and I have driven it for about 2 hours since I got it home and nothing is acting up, but I know it will when I least expect it.

 

Fuel Pump..... it only acted up when I was low on fuel and had been driving for a while. I was told that the fuel in the tank helps to cool the pump, so when you are low on gas, it doesn't cool as good. Which explains why after I let it sit for an hour or so, it runs fine. It did start acting up on me again, so I let it sit for two hours and it ran fine on the way home where I replaced the fuel pump.