Idle, surging, bucking, emissions, CEL mess...

[Aerie]

Hello, all.

I've got a problem with my '95 Talon TSi FWD. I'll try to lay it out as best as I can, so forgive me if I'm long-winded...

It started a few weeks ago with an undulating idle that would cycle from 1100-1600. Then occasionally cycle a little lower than that. Just about the time I was getting sick of it, it stopped on it's own and was followed by a CEL. The scan tool said "Idle System Malfunction". I don't remember the code, but I think my manual referenced the IAC for it.

Why not the best way to go about it, I cleaned up the TB and cleared the computer as I had emissions coming up. Since my symptoms were gone, I figured all would be all right. Flash to yesterday, and I'm headed out to do my emissions test. Right at startup it's idling around 450 rpm and it's grumbly and stumbly. Not a thresher idle, but not good. It stays this way through the temperature range. A bit later as I'm headed up the highway it starts running poorly at cruise and under load. Not quite surging, not quite bucking, but somewhere in between, kind of like driving into a nasty flapping headwind. This is the case at all RPM in my daily driving range.

It also likes to die when I come off the gas and out of gear sometimes.

Then, my emissions test. I failed on hydrocarbons. Not terribly badly, but my resulsts are as follows.

Test Limit Result P/F

THC 1.20 2.21 Fail

NOX 3.00 1.01 Pass

CO 30.0 4.1 Pass

CO2 n/a 562.3 n/a

Then finally, on the way home, my CEL comes back.

And of course, the Explorer they were running in the other lane never broke 2500 rpm, and my Talon on the other side was hitting nice BOV inducing, hi rpm boost.... bastards.

Anyhow, if anyone could guide me in a particular direction, it would be fabulous, as I have the choice of driving with expired tags or taking the bus 27 miles to work. I'm also sitting on an EVOIII B16G, 550's etc. until I can get this cleared up...

I've done a cursory inspection for vacuum leaks. There's nothing obvious but I haven't done a full vaccum test. Would this be the first thing to do or is there something notorious I'm missing?

I'm running just about stock now, too. Just intake, piping, and an MBC currently. Thanks!

 

[sumenlo]

If the code you pulled referenced the IAC valve, you should check that and replace it. It's a cheap fix from your local Auto Zone. I had a similar problem back when I had my old school civic. I would replace the IAC for starters and then go from there. Most of the time that will effect your emissions too, so that's what I would do.

 

[justin0469]

Most idle issues in our DSMs are solved by replacing the ISC. Search for ISC on here and you will find endless info. www.dsmparts.com and i think slowboy has them because of how common they are to replace.

justin