While sitting in traffic, my engine tends to over-rev itself a lot. The tach just jumps lots between 2k and 3k, very erratic. If I tap the accelerator, it'll jump up and sometimes drop lower than that, but only to 1400 or so at lowest and it will still be erratic and probably start rising up again if I just sit there much longer. It's got to be murder on my clutch as I pull back on the pedal always in the 2-3K range, so many times.

This has only ever happened in stop/go traffic. The problem goes away as soon as I start moving for real again (get out of traffic). Anyone know what causes it? It's happened a few times since I got the car 2 years and 50,000 miles ago, so it's not new... I'm just finally asking now.
-N

 

If you have your AC/ Heater, radio, espcially a aftermarket system with a sub and an amp, with your lights going this might happen. From my understanding, and from being in other peoples cars who have subs and an amp, sometimes the drain on the electrical system is enough to make the car rev to produce enough power to compinsate.

I could be wrong... But then again, I could be wrong... I'm most likely wrong.

Fox

PS- I used to have a similar problem with jumpy idles before my grounding kit was put on. but not as drastic as what you have going on.

 

I didn't have the AC/Heater on and while normally I've got a subwoofer, it's a small setup (only 300W or so). And when I noticed this this past weekend, the sub wasn't plugged in. Any other ideas??
-N

 

what mods do you have?

 

Nothing really... my profile lists it all though, but nothing engine-related.
-N

 

I think it's just part of our car. My car will do it as well but it won't rev that high. Mine will only go to about 2k. I have asked my dad and he says it's computer controled b/c of the PS, radio, etc.

 

Well, I know that our alternator isn't the strongest around, but if the engine were revving to get the electronics system better up to snuff, then I'd expect more consistent behavior. If the ECU wanted the tach higher at idle, then it would stay a little bit more in one place and it wouldn't drop so erratically when I tap the accelerator.
-N

 

you have a vac leak

 

A vac leak is possible I guess... but wouldn't the tach drop to almost stalling then? And wouldn't that be more consistent, like whenever I idle, regardless of speed or length of time?

When this stupid rain stops, I'll go and make sure all the intake is tight and all, but with this having been going on for so long, it's doubtful anything is loose and hasn't just fallen off by now.
-N

 

try resetting the ecu

 

Well, it's not doing it now, so I wouldn't be able to test that resetting the ECU would work. And I'm not likely to get out of traffic and stop on the side of the road to test it when driving. Once I'm up to speed, it's normal again, including at stoplights and normal moving traffic. It's only after 10-15 minutes or so sitting in traffic that this happens and that doesn't happen very often... just happened to get caught a little on Easter.
-N

 

I'm not familar with the lancers, but check to see if your car has an ISC motor. (idle sensor control) When they start to go bad they will rev the engine by themselves up and down. Like I said, I have no clue if the lancers even have them but I would check just to be safe. If you have an ISC it should be located on the side of the throttle body. It will have have a wiring harness plugged into it. My last suggestion would be what someone else already said, vac line is off. Good luck.

 

i currently have the same problem, exactly! if anyone has any help please let us know. mine might be more complicated than hers on the account of a greddy emanage and a cam.

 

As EVIL MR said, I would also guess vaccuum leak.

 

i have had the same problem while sitting in traffic.. I would definitely check for vacuum leaks.. b/c i think my aftermarket intake was always to blame..
If not it must be something inherent to our cars.