Weird Problem

Ok, this one has got me and my mechanic totally stumped. First, it's a 95 Formula LT-1 with a year-old engine rebuild that I have had no trouble with. For the past month though it has been having a problem with rough idle and poor acceleration. This only happens when it heats up to normal operating temperature. There are no computer error codes being generated by the problem, but it seems to be getting worse. I have replaced the coil, ignition module, and MAF sensor. Fuel pressure checks ok at all times, and rises as RPM's do. Since there are no codes, I assume that the engine sensors are all reading OK. It has to be something affected by engine heat. Could an injector be getting sticky as it gets hot? They all seem to be clicking at the same rate at idle. I'll pull the fuel rail off and check them out if I have to, but would appreciate advice first.

PS: GTP Dad, I still remember your advice on the fuel regulator from a previous post. It doesn't seem to be the fuel pump, thats for sure. If I pull the fuel rail, I'll try to test and/or replace the regulator. Thanks again.

How many miles are on your injectors? I had a problem years ago that the engine ran fine until the engine heated up. Once that happened the injector resistance would go so high that they would not work properly and I would lose power. Once I replaced all the injectors the engine ran great. Of course that cost me a chunk of money for new injectors but I really didn't have any problems after that. You may want to do a resistance check to see what is going on with your injectors. Of course if they are bad the only way to fix the problem is to replace them.

The injectors are the originals, to my knowledge, and have about 164K miles on them. That makes sense, after all heat produces electrical resistance. I think I read somewhere that the normal injector resistance for an LT-1 is about 12-14 ohms or so, right? I'll heat up the car and check 'em.
Thanks, I'll let you know what I find.

Could be the EGR too...that might not affect anything until the car warms up as well and I don't think it would trip a code either.

Turns out it was just the damn spark plug wires. My mechanic took off the opti-spark distributor to check it, and noticed the wires were kind of burned on one side. When the car heated up, they just stopped conducting right. Runs like a champ now. Anyway, thanks for the advice guys.