PCA Forums

PLEASE HELP!! '92 Safari 4.3L TBI running bad in "closed loop"

My Safari runs SO bad once it warms up and goes into "Closed Loop." It set codes for the O2 sensor, so I replaced it. It's slightly better, but still runs bad in "closed loop." It's getting too much gas into the system at a "light" pedal, but if you hammer down the pedal it's not so bad, but of course one can't drive with the pedal to metal. I'm stumped on this, so if you can help out here, it would be a Godsend.

Thanks in advance!!!

sounds like the throttle position sensor might be screwing up or it could have a bad MAF if it even has one. Also there should be a coolant temp sensor for the ECU. Not the one for the temp guage. Those are known to fail as well and cause rich or lean conditions. Best bet is to buy a manual for it with testing procedures.

yeah everything has been mentioned that i can think of.

As stated above, coolant temp sensor (or air in your cooling system)., bad MAP sensor, a loose vacuum line, perhaps a leaky injector.

Unlikely from your description, but possible, - clogged cat.

yeah forgot about that one.. that will also eat O2 sensors up.

Does it have the large solinoid type egr valve on the front of the intake manifold around the thermostat housing? If so, it is a common problem for a large chunk of carbon to get wedged between the plunger and the seat. Usually causes serious runnability issues when warm, excessively rough idle is the most common fault if it will idle at all. If it doesnt have this type of egr valve it will still run pretty rough if the diaphram is ruptured. Most the ones you get from you local autopart store will not cure it and they usually require some sort of shim to make them work at all. I am a firm believer in dealership parts even though they are high as a giraffe's pu$$y. Also mentioned above the coolant temp sensor. There is usually more than one so you have to make sure you know which one is the culprit if it is bad. Reading the data stream from a snap on or otc scanner will tell you more than codes will. An oxygen sensor code is usually generated from another fault unless the heating element has shorted or burnt up. On the older model gm motors like that troubleshooting can be a real nightmare. Surprising enough, a leaky throttle body gasket will cause an oxygen sensor code.

vacuum, map sensor, coolant sensor for ecm likley causes. Do you have access to a scanner to read data stream? Defenatly invest in good manual (not one at autozone or oreilys - waist of money and you will not get the information your looking foor)