Cadillac Repair: Engine swap gone bad, ability area, catalytic converters

Question
Hello,

This may not be you ability area. I have a 1990 caddy seville that had a 4.5l engine go out on it.After checking around I was told by a few people I could place a 1990 4.9l engine in as a replacement which was fine as there were more to get around here in Elgin, IL.I had the engines swaped but it never came out right. The catalytic converters which I replaced at engine swap time went cherry red and burnt up.The engine idles rough at about 1250 rpm on the computer monitor in the car but will settle down to 650 after running for awhile. The engine is dogged and eats fuel like it was being pumped out. My question is should I switch computers in the car also as they weren't swaped and I was curious if the original 4.5 computer was sending wrong info to the 4.9l engine causeing all the issues or if there is another solution.Only light I get on the dash is low refrigerant as I never refilled ac after swap?Thanks

Answer
You most likely destroyed the 4.5L computer because the 4.9L engine was running to lean and fried your cats.

You can TRY but I do not hold much success by installing the 4.9L computers, ECM and the BCM into the vehicle to match the engine.

The wiring is different between the 4.5L and the 4.9L computer systems and you would have to check each and every wire from both vehicles to make sure that they match exactly. Your talking about days of work.

If you have an OFF and WARMER buttons on your A/C-Heater display get your self a paper and pencil and:

1. Ignition ON, Engine OFF.

2. Simultaneously push and hold the OFF and WARMER buttons for 2 seconds and then release.

3. Write down all the letters and numbers that display on the screen and let me know what they are.

4. Turn ignition OFF.


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