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1981 Cadillac DFI engine runs much too rich

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Hi to all!


I am frustrated. I have worked and changed a lot of parts at my 1981 Cadillac Fleetwood with DFI. But now : The engine will not start.


I have already a long topic here (


The main problem was : Too rich running engine! It was not possible to read the error codes. ISC not working.


I did this in the past :


Put in new injectors

Rebuild the fuel pressure regulator

Adjusted the TPS

Changed the MAP Sensor

Checked the TPS

Checked the engine coolant sensor


Since the ISC was not working I disconnected it finally and set the engine idle speed around 800 rpm. So the engine run not bad but on the street, it had some power “holes”. It seemed that some ignitions were not there.


OK, so I decided to order a new ECM and ISC. Today I built in the ECM and ISC. At first, I wanted to check the error codes. I switched the ignition on and then the heater fan started to run. I switched it off, pressed down the “OFF” and “Warmer” button. After a short while, these two dots were shown. And that’s it… no 88 to check display or codes. After a short while, the fan started again…


I decided to start the engine and it started right up. It seemed that the mixture was not too rich but one or two cylinders worked not. I thought, that this was a problem from the last drive and started to check the spark plugs and some were wet.  I seemed that somewhat was working in the ISC as the engine was running.


After cleaning the plugs, I wanted to start the engine, warm it up to adjust the ISC as described in the shop manual.


But now, I have the problem, that the engine will not start. Here and there is an ignition but will not run. I checked again the plugs and some were wet. And I can clearly smell the fuel of the throttle body but there is no leak.


I hoped, with these new parts I have the solution but at the moment I am more far away from the solution as before.


Today I had the chance to start again with cold weather but after a short while the engine run slower and slower because one cylinder after the other was flooded by gas and several spark plugs were wet. Mostly the ones in the middle of the cylinder heads.  With just one injector, the engine is running but with two, in warm condition it goes off. This is a new situation since I have the new ECM and ISC.


The ISC is not moving but it is ok, I have checked the motor and the switch of it.


Has someone an idea?


Kind regards



Edited by ThomasBorchers (see edit history)

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