89 century runs rich after warmed up(no response on century forum)

hello,i know this is the lesabre forum but i couldnt get a response after several days on the century forum, any help would be apreciated. i own a 1989 century with the 3.3 liter, heres the problem. the car started running eratic , so i brought it in they replaced the computer, it ran great for about 2 months then after warming up one morning started stumbling and acting as if were running rich, engine light came up, and codes were o2 sensor and m.a.f, so i replaced both, while i was at it i replaced the fuel preasure regulator and tps, all new parts. i still get the maf code, even after swapping it out once again with another new part. runs great until warm, then stumbles and smells of fuel. plugs are black as well. anyone? thanks in advance.

You could have a bad cam sensor. They control the injector pulse timing. It could also be a bad CTS (Coolant temp sensor.) It has to sense the engine temp to control fuel delivery during cold start and warm operating conditions.

ty i'l check that as well. today i started the car, again it ran fine until warm then started running terrible, there is black smoke, and gas dripping from the tail pipe. running rich obviously, but cant figure out why.

ty i'l check that as well. today i started the car, again it ran fine until warm then started running terrible, there is black smoke, and gas dripping from the tail pipe. running rich obviously, but cant figure out why.

Do you have a data scanner? I would take another look at your MAF circuit and verify that everything looks okay there.

Do you have a data scanner? I would take another look at your MAF circuit and verify that everything looks okay there.


hello stuzman, no i do not have a scanner, just checking codes the ole fashion way reading the flashes. the only code that comes up is "34" . the engine light comes on about 5 seconds after i strt the car, runs geat until it reaches normal operating temperature then acts as if it is getting the wrong mixture. is it possible i have a bad maf sensor wire or connection?

hello stuzman, no i do not have a scanner, just checking codes the ole fashion way reading the flashes. the only code that comes up is "34" . the engine light comes on about 5 seconds after i strt the car, runs geat until it reaches normal operating temperature then acts as if it is getting the wrong mixture. is it possible i have a bad maf sensor wire or connection?

Yes, it's possible and I would take a look at the signal being fed back to the PCM to ensure that it's working correctly. I would assume that the MAF sensor on your vehicle is using a variable frequency to be measured by the PCM. The PCM is looking at the frequency of the MAF and from that determines the air flow. The code is coming up because the PCM says the air flow is too low based on the TPS and RPM of the engine. If you have a DMM which can measure frequency, take a look at the signal back to the PCM from the MAF. At idle, it should be around 30Hz and the frequency increases as the engine speed is increased; somewhere around 150Hz. You should see the frequency going up as the engine is accelerated. If this looks good, you still can't be sure the PCM is seeing the same signal (maybe a bad connection to the PCM for this signal, or even the PCM could be bad). If the signal comes up good, take a look at the PCM for the same signal. If this looks good, take a look at your TPS to ensure that it is working okay.

I see that you've changed the PCM and TPS, so hopefully those items are okay. Good luck with your repairs and keep us posted of your findings!