Possible O2 sensor (Upstream), you would need a scan tool to watch it during the vehicles surge.
rpms at highway speed surging
At steady highway speeds (typically 65-75 mph), the rpms will occasionally surge with a loss of power feeling. For example, with the speedo at 70 mph the tach sits at 2200 rpm. All of a sudden the rpm will briefly rise to 2500 rpm and drop back just as quickly. When it does this, it feels as though the transmission disengages. On a 40 mile commute it will do this probably 10 times. Truck is a 2000 V6 4WD with an auto tranny, about 125k miles. I wouldn't think it's the tranny going yet and would lean toward some sort of sender/sensor, but I just don't know. The tranny was flushed last around 100k. No check engine lights on. Any ideas? Things to check?
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Do you have the electronically-controlled transmission (ECT)? Does this surging behavior occur when you have the ECT 'Power' setting engaged?
I've got a really simple code scanner, I'll check but I'm not sure that it can read real-time. As much of a pain in the butt it would be to change the upstream sensor out, I'd rather do that than deal with tranny issues (plus it's old enough it could definitely benefit anyway).Possible O2 sensor (Upstream), you would need a scan tool to watch it during the vehicles surge.
I do have the ECT, but I've never used it.Do you have the electronically-controlled transmission (ECT)? Does this surging behavior occur when you have the ECT 'Power' setting engaged?
Update: Today I got a check engine light, code scanned P0120. From doing some reading, it appears the throttle position sensor has gone bad. The truck has been idling a little weird lately too, doing the same kind of surge thing to a lesser degree, so this would make sense. I just ordered the TPS and some maintenance items (belts, air filter, etc), so hopefully I'll be good as new next week when they get here. It could still be the O2 sensor, but given the code it's probably the TPS.
Thanks for the assistance guys!
Thanks for the assistance guys!
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