This is the third installment in my 1990 740GL wagon with Rex/Regina ignition. Here's what I've done thus far:

Intake cleaning (throttle body et al.)
Checked for vacuum leaks (none found)
Cleaned battery posts and all contacts, including main ground
Cleaned grounding trees near front edges of car
Compression test = 150psi give or take 2psi in each cylinder
Catalytic converter and exhaust system is good with no blockage
New engine temp sensor (OBD I said it was bad)
Air intake temp sensor tested good
New plugs and plug wires
New distributor cap and rotor
New fuel filter
New air filter
Fuel suppression relay good
Fuel injection relay re-soldered
Taken fuel pressure regulator hose off--no smell of gas or any visible gas
Cleaned grounds at fuel rail
Had a new CPS installed about three years ago
When I replaced the spark plugs, the old ones looked good, without indicators of running lean or rich.

Currently there are no codes in the OBD system.

I've probably done other things as well, but that's what I can remember right now.

The history: Car was running wonderfully for the past few years, minus a short time when the O2 sensor needed replaced a year back. This summer, the car suddenly began having the issues that still remain. Nothing I have done has seemed to help the general running condition of the car.

Current symptoms: Car does not like to start in cold. When a bit warmer (pushed into garage), it will start. Idle is alright for a few seconds. Then idle becomes erratic, mostly dropping down to around 400rmp then jumping up to 800. It doesn't stall.

When driving, the car lacks power and REALLY surges on initial acceleration. The surge has little power associated--it goes from not really moving to a slight crawl. The engine has immense problems right off of idle. It will sometimes rev alright and have good power for a few seconds when accelerating while driving, then I can feel the power drop.

I'm getting frustrated with the beast. There is fuel and spark, and it DOES run, but it seems there's some specific issue that I'm missing. Could this be an ECU issue?

Any help is GREATLY appreciated!

thanks,

Nate
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1997 850, 1979 242GT, 1990 740GL