[Caemgen]

1991 Toyota Celica GT, 2.2L DOHC, 5spd Standard, CA

Was off the road for a long time, just putting it back:
Replaced the engine
Replaced fuel pump
Replaced fuel filter
Replaced injector
Replaced plugs and air filter
Replaced radiator
Replaced various hoses/lines as necessary

Ran fine.

Filled fuel tank.

Start is extremely rough (most of the time) in the morning. Pedal to the floor gets me around 2500 rpm and choppy.

Pumping the pedal gets SLOW response to increased fuel and extra chop.

No lights or codes of any kind.

After 2-4 minutes, the engine responds perfectly as though nothing is wrong, and there will not be another problem until the car sits at least 5 hours.

Two days ago had a 4 minute wait for the engine to catch when leaving work. Went immediately to smog test the car on a dyno 5 blocks from work. Passed near perfectly. 15% CO2, 0% O2, 16ppm HC, 02% CO, 10ppm NO.

Friend put spray in looking for vacuum leaks, but it was running fine and there were no leaks in the vacuum system.

He also took out and cleaned the fuel regulator, it was fine, but he cleaned it anyway.

He couldn't get the car to fail.

Today after work, car sitting a full 8 1/2 hours, started perfectly.

When at its worst, sounds as though it is firing out the exhaust valves. Otherwise just hollow and choppy. Smells off when this is happening. When it is making the back-fire sound, there is also a cloud of crap out the tail pipe.

All the while, no code, no lights.

I have a guess from reading other posts and stuff on the internet, but don't want to lead anyone astray with any and all ideas.

Thank you

[TxGreaseMonkey]

. Replace the Ignition Control Module (ICM).

. Replace the ignition coil.

. Check/replace the Engine Coolant Temperature (ECT) Sensor.

My bet is the ICM is intermittently failing, which sometimes allows unburned gas to build-up and it is then detonated. Be careful it doesn't blow the exhaust system off the car. Plus, this can easily destroy the catalytic converter, if it's not fixed soon.