88'Comanche Posted March 14, 2015 Share Posted March 14, 2015 Hey everybody, new guy with a couple questions.. I bought my 88 2.5L SporTruck about 2 years ago and the last 5 months it has been sitting. When I fire her up it idle's fine until it warms up then will chug itself to death. If I try to get on it, it falls on it's face and will occasionally backfire. Seems like it's flooding itself out when it comes to temp, what could cause this problem? Any help is appreciated! Link to comment Share on other sites More sharing options...
dasbulliwagen Posted March 14, 2015 Share Posted March 14, 2015 Mine did something like that till I replaced the o2 sensor. Mine had sat for 4 years and nothing fixed its running issue till I put the o2 sensor in it. Link to comment Share on other sites More sharing options...
88'Comanche Posted March 15, 2015 Author Share Posted March 15, 2015 I replaced my o2 sensor about 9-10 months before this started happening, are they notorious for going out? How long is an o2 sensor good for? Link to comment Share on other sites More sharing options...
Eagle Posted March 15, 2015 Share Posted March 15, 2015 The O2 sensor is supposed to be good for approximately 80,000 miles. Being an '88, your truck has a Renix ignition and injection system. If it's set up similar to the 4.0L, in addition to the temperature sensor on the head that sends data to the temp gauge, there should be another temperature sensor down on the left (driver's) side of the block. That's the one that sends temperature data to the ECU, and that's what determines when the ECU switches out of open loop (warm-up) mode into closed lop (normal run) mode. In warm-up mode, the system runs in a rich condition. After the engine gets to normal operating temperature (actually, a bit before -- around 165 degrees) the ECU kicks in and starts controlling the injection. First possibility is that someone put in a cold thermostat, and the engine isn't getting warm enough to switch to closed loop mode. That'll cause a rich condition. Saw it on a trail ride some years ago. Guy had a 4.0L. He hit a rock and broke his exhaust header. The exhaust leak caused the ECU to think it was running lean, so it started injecting a lot more gas. It didn't all burn in the cylinder, so the exhaust was pumping out burning fuel -- so much that the header pipes were a bright yellow-orange color. So you might have a bad thermostat, or you could have a bad temperature sensor on the block. Link to comment Share on other sites More sharing options...
88'Comanche Posted March 15, 2015 Author Share Posted March 15, 2015 Alright well they are fairly cheap I'll pick one up tomorrow and see if that changes anything, thanks. Link to comment Share on other sites More sharing options...
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