Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
we have a 92 saturn sl2 dohc in the shop it came in on tow with a bad engine we replaced the engine with a used one 60k miles engine runs great except at about 1500-1700rpm. If you hit the accelerator fairly quickly it revs up fine but if you ease into the throttle its fine before and after this specific rpm range of 15-1700. integrator at idle is 128 and block learn is 108 , while the throttle is pressed at 15-1700 integrator drops down to 70-65 and the engine obviously runs rough. the throttle position sensor , IAC have been replaced . we did find the ECT sensor and pig tail where causing a problem before we performed a wiggle test on the pigtail and the temp would fluctuate so we replaced those. the map sensor had carbon built up in the port so we replaced it aswell its progressively gotten better but we still have this issue at 1500. We have a triton d8 scanner with 2 channel scope but we arent proficient in using it that is why we have joined this program we did scope the map sensor signal and the wave form would spike .5v to around 1.5v at idle and when it was acting up it would spike up to around 2.5v . any tips would be great thank you in advance
1500-1700ish rpm almost sounds like an rpm that the purge valve would open. Maybe it’s sticking if it has one being that old I can’t remember. If it has one I’d cap off the line and retest.
Topic Author
