Hello everyone,

I'm hoping that someone on here may be able to help me with this problem, as I'm just about out of options and do not have access to the factory corvette manuals. I have a 1994 lt1 corvette. It has an ignition problem that is driving me off the wall. When the vehicle sits outside for an extended period in the heat (and by hot--I mean 100 degrees heat or thereabout), sometimes (and that's the most frustrating part!) the vehicle power bogs down, especially around 1500-2000 rpms. Additionally, when it is running like this, when you take off quickly from an idle, the car will just barely move forward and then get a big surge of power. Finally, the car gets hot after all these driveability problems start, going north of 240, whereas it normally stays below 210 before it starts running poorly. I've monitored the problem with a scan tool, the computer is retarding the timing around 9% when it starts to bog down, though I have not yet heard any spark knock.

As I mentioned above, this problem only occurs sometimes in the heat. At other times, it runs very well. What most often happens is that I drive it for around 30 miles with no problems at all... the temperature is good (i.e., below 215) and the motor runs wonderfully. However, after I turn the key off and leave the car sitting for a couple minutes, it will run badly (though the idle is still generally ok and higher rpms are ok, a loss of power is evident from 1500 rpms up).

Initially, I suspected a problem with the knock sensor circuit, so I replaced the knock sensors in the block and the knock sensor control module w/ a lt4 ks control module. No luck. The car had had the optispark taken off in the past and replaced with a delteq coil pack ignition system. So, I figured that the delteq setup may be the problem. I replaced that with new plugs, wires, ignition coil, and a new optispark distributor--first a rebuilt unit from a local parts house, then a new ac delco unit from ecklers. The same problem persisted. Next, I figured it had to be a problem with the computer. So, since I could not find a new computer to buy, I sent my computer away to a place that was supposed to rebuild it or junk it if it was beyond saving. They sent the computer back and said it was rebuilt, but, of course, I cannot be absolutely certain what exactly they did to it. I've replaced a number of other things in an attempt to solve this problem (e.g., a throttle position sensor), but to no avail; I've listed the major services performed.

The onboard diagnostics system has not given me much help. At one point, there was a code in the computer for an oxygen sensor. I replaced the sensor and the check engine light went away, but not the driveability problem. Just recently when the car was acting up, I noticed a "sys" light flash on the dash. After doing a little research, I realized that there was a code in the computer for this light, which I could access through "central control" diagnostics on the scan tool. The code was "041". I guess that this may be the best lead that I've got on fixing this problem. Does anyone have a factory service manual with the diagnostics procedure for a code 041? Has anyone else had a similar problem to mine? Help me corvette forum; I'm running out of ideas!

Thanks for reading! Any help is greatly appreciated!

 

I would try to get it to act up with a fuel pressure gauge taped to the windshield, make sure you have good connections! good luck!

 

Is code 41 the only one you've stored in the ECM? Could be a faulty ignition coil or bad Ignition Control Module (ICM). Both or either can make LT1's act squirrely under heat soak conditions.

But, I agree with Red 91. See if you can see what the fuel pressure conditions are before you start throwing money at parts and by all means, BUY the Factory Service Manual (FSM).

Check on ebay. I purchased both books in very gently used condition for my '92 this past Spring for $50 bones (plus shipping).

 

I'm thinking coil or ignition module. If not that then the opti is bad/ breaking down. Good luck.

 

If you haven't changed the coil and ICM try that first.

Otherwise welcome to my world! I still haven't found the cause of the issue afte 5 ICM's and two coils. It still acts up in the heat, runs fine when its cool out.