What causes a 1990 Cadillac deville to loose power?

Answer 1

i have a 1990 casillac sedan deville with a 4.5L V8 that I bought 8 months ago with only 98xxx origional miles on it. Shortly thereafter the service evgine soon light comes on and dsince I am a service tech I take it by work on my day off and ron the OBD1 on it and it came back with a code for the map sensor, that took all of 5 min and I thought all was well. Then about 4.5 months ago the light came back on. I checked it out again and it came back as an O2 sensor downstream. Then one day out of the blue it starts stalling out when you are sitting at a red light, then about 3.5 weeks ago it went totally crazy and would stall out while still going down the road at 30-40 miles an hour. You just shift over to N and it would fire back up, then shift back into drive and continue on your way. Finally I just couldnt take it anymore and took it to this real good drivability guy that I know. We talked and agreed that it wasnt breathing right from one end or the other so he sent me to this exaust shop to pressure test the cat. They said it should be between 2.5 and 3.5 and it was at 6lbs. of backpressure, enough to need to deal with it down the road but not my major problem at the moment. I take it back to the drivability guy and after 3.75 hours he comes bach and tells me that its my fule injectors on it, that my #2 cylender injector is shorted out electrically and wont fire at all ant that the #1,3,6 were shorting out intermittantly and missfireing and that that was what my problem was. I found some good rebuilt injectors and changed them out and cleaned the fule rails and was sure all of my problems would be gone. That was sunday, and here it is Tuesday and I am still having significant problems. Here are the current symptoms: It has a slightly high idle in Park, a OK idle in Neutral and a very high pulling idle in OD. To come to a stop at a light you have to use way more brakes now than before, and while stopped at the light it is as if the idle is so high that you have to fight to keep the car stationary and you can be going down a straightaway that is flat or slightly inclined and the car will accelerate without your foot on the gas. Yet with all of that it seems to be significantly lacking power. When at 50-60 going down the highway it doesnt have much in the way of passing power and when you do put your foot all of the way into it it shifts back and forth very roughly between what I think is 2 and 3. Then today I stoped in to get gas and when backing up to the pump it stalled out again 3 times. I kind of accredited it to low fuel and went in and put 10 gallons into it and left the gas station. The road that I was on was a decient hill but only maybe a 4%grade and there was no power at all it was struggling to do 2mph and kept stalling out at that. After taking 25min to cover 130 yards I finally got to a sidestreet and turned off and costed to a stop on a flat spot in the road. I checked to make sure that my fuel lines into the fuel rails were tight and that the injectors and rails were well seated and secure themselves. Eveerything looked good there was no fuel smell, I got in and it started right up and drove fine the rest of the day. I tried checking it for codes again and nothing. When the guy did the diagnostic on it he checked the spark and the compression and said that everything looked good. I dont know if it could be a TPS or the whole throttle body or the fuel control moduel. What do I need to check into next?