running rich

[89sub]

I posted this question before but I still need help. My 89 Suburban is still running rich. I pulled the codes (12 and 45--if memory serves) and only code indicated rich condition at O2 sensor. My spray pattern at TBI injectors is good--except there still is a drip at center of cones. They are NAPA injectors--brand new. Tech ran diagnostic on engine and found everything to be okay. He checked for vacuum leaks with pressurized smoke and found nothing. ETS (temp sensor for ECM) is new, as is the fuel pump. Fuel pressure is okay. EGR is okay. All other sensors checked out okay.

My question is this: could the fuel pressure regulator cause this? Does the engine run rich and cause the injectors to drip because of something else? My coolant system has a leak; won't stay pressurized--would this cause the ETS to see lack of coolant and open injector pulse? I am at a loss. Engine is a 22,000 mile old GM Mr. Goodwrench installed at a dealer 18 months ago, with a new distributor and (I believe) all new sensors, according to invoice.

Thanks in advance for your comments

[maxwedge]

Has it been scanned to look at the cts readings, the map sensor input, has the fuel pressure been tested? Does the engine have good vacuum?

[taillight]

Check for 5 volts at the sensors. No less. Check for grounds at the computer. Either low voltage or bad grounds could cause a rich condition.

[twistedtech]

I got bit in the butt a few years back on this. I had a customers tbi apart 3 times. I never seen a thing that was not right. I also dont rebuild tbi's. I took the tbi off my submarine that worked great, well so did his truck. Tossed on a used tbi and all was good. Just had a truck in last fall that did the oppisite ( was lean ) tossed on the tbi from the SUB and it ran strong. Again put on a used tbi and he is more than happy. This truck had been to 3 shop's and nobody got it. I hate used but it seemed to have worked out for now.

[92K2500]

The tech looked at the engine computer with the truck running with an expensive computer that allowed us to see "realtime" what the ECM was seeing (all sensor inputs) We tried everything; he checked for vacuum at the EGR valve with a mightyvac, the spark, the voltage inputs/outputs at the CTS (ETS)/MAP/O2 sensor. The fuel pressure was checked; I am just not sure it was done in a manner that looks at the pressure regulator. The fittings at the back of the TBI aren't easy to get to to check this. This all happened on our family trip to Reno where we found a good tech. I may have to run to a dealer shop to sort this out. Thanks for the comments!

[89sub]

Well, I just heard from the local GMC dealer: the main computer and chip took a dump. $687.00 for both. Oh, well, it's just money and we can't take it with us (although I think I will be buried in the dumb thing!) Thanks to all for your responses.