Car is idling funny, with no pressure on gas it goes up and down on it's own. It is in a pattern and the jumps are all the same going from .5rpm to 2.5rpm with the same amount of time between each one. I was thinking it might be an ECU problem because of the decrease in backpressure from the exhaust upgrade. It has 2.5" exhaust with the cat punched out (test pipe) and a 3.5" resonator muffler, needless to say it is getting annoying. Unfortunately I did not do the install, the person my brother bought it off of didn't say anything about it and my brother got a good deal so he didn't question it. Any suggestions/info on cost to fix? Thanks.

 

My friend had a problem like that in his 93 Ford Probe GT. Our mechanic had
to adjust the TB cable and then it was fine.

 

What exactly did he have to do to it? Is it something I can do myself or not? If I could save the money by not going to the mechanic that would be great, esspecially since I told my brother I would take care of it for him for his Birthday present.

 

First reset the ECU. If that doesn't work, take it to the dealership and have them check it out. No sense in worrying too much about something you can have fixed for free...and by someone else.

EDIT: BTW, the throttle body should have very little to do with the idle in the Lancer. Idle air comes through an inlet called the idle air control valve (or something like that...my brain's shot) and is controlled by a stepper motor. If anything the stepper motor may have gone bad.

Oh yeah. And does the car have an aftermarket intake on it? I found my idle sometimes did similar things (though less extreme on the high end) when I had a cold air intake installed.

 

First thing you should do is check that everything is plugges in properly, then check your air filter. Is it damp or dirty? If so then clean/replace/dry as nessessary. If not it might be something as simple as dirty plugs. Pull them out, check them (make sure they arnt burnt or cracked) check the gap, clean them (regardless of how they look) and re-install. If the plugs are dammaged then buy new ones and be sure to check the gap. (specs are in your manual)

If this doesnt work I'd get some injector cleaner.

 

i had that problem when i had a b16 in my civic it ended up being a couple things causing the problem 1] o2 sensor was broken 2] vacuum lines were leaking.