Cadillac Repair: 1990 Cad.Seville Possible ECM problem, throttle position sensor, diagnostic time

Question
Driver info. center showed sevice car soon, plus system failure. Car stalled, or sputtered until stalling. Manuel said computer problem. Took it in changed body computer, engine chip in engine computer. Problem still occuring. it is intermitent, does not happen all the time, but sooner or later it occurs. Suddenly car will sputter not run. Will not then suddenly everything is normal, then it happens again. After failure of local mechanic took it toCad. They would not work on it because i took it to a private party first. Help, i need my car

Answer
Hi David, What code(s) did you get that you determined that you had to change the BCM and the ECM prom? Caddy had a problem with the engine battery ground cable that is located near the starter. Taking the cable off and cleaning the cable end and block with sandpaper or wire brush and then doing the same to the L shaped starter bracket so you get rid of the black paint at the bolt and cable end at the starter end might be all that is needed. The fact that the caddy dealer doesn't want to touch it after an independant worked on it first is sure a cop-out. Maybe they might charge more diagnostic time but certainly not turn down the job. Also there was a problem with the throttle position sensor on the '90 model 4.5 liter engines. If yours has a flat surface instead of a chamfered endge on the half circle end then replaceing it might get you going. The system is rather complex as you are finding out and there are several other things that can be bad and show the same symptoms. Checking fuel pressure, injectors for shorting and fuel flow and reading the data that the ecm is seeing are all things that can isolate the problem area but without the tools and knowhow it gets very expensive replaceing parts. Too bad you weren't near Rockford, Il. I could take a look at it. Try the neg. battery cable cleaning, look at the tps and if you are unsure how to read the codes or want more help then repost and I'll do my best to help. Bill