runs badly

[89sub]

Help! My 1989 Suburban's check engine light came on recently. Before it did, the idle RPM started creeping up to about 1700 RPM. Once the check engine light came on, the idle came back down, but now it runs like crap. I had a mechanic look at it; code 45 rich O2 sensor was pulled from ECM. We checked: O2 sensor, EGR valve, new temp sensor, MAP sensor, EVAP system, TPS, and a few other things I might be forgetting. The next thing he wanted to replace was the distributer (new 22,000 miles ago, as was the engine from a Chevy dealer) and the ECM. Didn't replace either due to time constraints. What it is now doing is laying down,running like a dog, running rich (code 45) and no power. We ended up (at my request) changing the two fuel injectors (throttle-body injected) because both were dripping inside of the spray cone at idle. It didn't help I should also mention we replaced the fuel pump and checked the fuel pressure at the TBI and it spec'd okay (16 PSI at idle/deadhead, 13 PSI when running) The exhaust backpressure was checked at O2 sensor location--it was within specs. The truck idles good, just showing a rich O2 via an engine monitor the tech had, but lays down when loaded. Mileage took a dump--about 5 miles a gallon due to the rich condition

Any ideas? This occurred on our family trip to Reno and, needless to say, ruined our weekend. I ended up leaving the vehicle in Klamath Falls and renting a minivan to get family home. Will retrieve vehicle home this weekend and take a look at it. Thanks for your response.

[2000CAYukon]

Make sure the MAP sensor is holding a vacuum, as well as, the vacuum hose to the MAP sensor. I had one of the rubber ends come loose at the MAP sensor causing the MAP sensor to report that the engine was under load and the ECM increased fuel delivery to the engine.

A bad engine coolant temp sensor can also cause too much fuel delivery. A cold engine needs more fuel than a warm engine.

A scan tool readout will help you diagnose both the temp sensor and MAP sensor.

//2000CAYukon

[89sub]

Thanks for your response! The tech had one of those expensive (OTC?) scanning tools hooked up to the diagnostic port while we were driving it. He monitored the ECM and said the MAP sensor showed okay. I believe he mityvac'd it, but I will put my mityvac on it when we get her home this weekend. Thanks again.

[89sub]

I forgot to mention: I did change out the temp sensor on top of the intake manifold (one with two wires) I am having trouble keeping coolant in the dumb thing (leak at cap for some reason), but it still does this when I have coolant level at normal. I also need to check/change thermostat, as my temp gauge seemed to be stuck at 150 degrees (obviously not working) instead of normal 200 degrees. Maybe problem?