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View Full Version : Fluctuating idle and fuel filter

red_sir
11-10-2005, 05:07 PM
I have a s13 SR and the idle is fluctuating on cold starts. It starts up right away and idles at ~1300rpms, sits there a good few seconds, then it'll drop to the point where the car stutters and almost dies, then jumps back up to 1300rpms and repeats the cycle. It does this for a couple mins until the car warms up a bit. It didn't use to do this, but it started right after I changed in a Z32 fuel filter. Seemed like a pretty easy install but I think I managed to mess something up. Any ideas what the problem is and is it related to the fuel filter install?

BTW, I'm running a microtech ECU (w/ map sensor) and the connector to the idle control unit (4 wires, 2 from the AAC valve, and 2 from the thing beside it) is not plugged in, it never had been, so I don't think my problem is related to that.
FlyingChicken
11-10-2005, 05:14 PM
does it drive?
red_sir
11-10-2005, 05:30 PM
Yup, once it warms up it drives fine.
FlyingChicken
11-10-2005, 05:46 PM
what kinda air filter you got?


Last time my car surged like that.. my MAF was broken
red_sir
11-10-2005, 05:58 PM
I forgot to mention, the microtech has a built in MAP sensor so it's definitely not a MAF problem either.
Romeyo07
11-11-2005, 06:11 AM
Sounds like the Idle air controller to me.
the head
11-11-2005, 08:33 AM
sounds like your 0 throttle maps are a little screwy have you been changing any of your ign or fuel maps lately? also could this be caused by temperature changes (season) my haltech gets a little surge in colder weather that is not there when it is warm, could also be that your cold start map needs a little adjustment
red_sir
11-11-2005, 04:34 PM
Sounds like the Idle air controller to me.

The IACV is the unit with the screw where you can adjust the idle right? How would that affect cold idle?
red_sir
11-11-2005, 04:41 PM
sounds like your 0 throttle maps are a little screwy have you been changing any of your ign or fuel maps lately? also could this be caused by temperature changes (season) my haltech gets a little surge in colder weather that is not there when it is warm, could also be that your cold start map needs a little adjustment

Nope, none of the maps have been touched since last winter when I got the car tuned. It's always idled fine on cold starts, even during the middle of last winter when it was really cold. And the weather hasn't changed much since the days before this idling problem. I just don't know whether it's a fuel filter related problem or something else went wrong and it was just coincidence that it happened right after changing the fuel filter.