MSM running an MS2 enhanced from Rev. Car has been running well...until. I drove to work fine, got in to come home and it immediately starting idling at 3000+.

I burned several older tunes, no change. Looked for vacuum leak...haven't found anything. Unplugged MS2 and replugged, no change. Reflashed just for fun, of course no change.

IAC? Any other thoughts? Getting a bit too hot out there to keep 'playing'.

I attached a short log just idling. I'm pretty sure the attached tune is the one used.

Thanks

 

disconnect iacv and see if it drops

if nothing happens, and you for sure don't have a vacuum leak, then yes, hte valve is bad

 

Here's a question, have you tried cycling the key while it idles high? Mine does this as well (mainly right after start up when cold), I'll cycle the key (quick on and off) and it will idle normally. There was a thread about this a few months ago. I haven't had a chance to log it, but it does happen for some reason.

 

I did unplug the IAC while running and there was no change.

I haven't cycled the ignition quickly.

It had been acting a bit goofy idling before this, but not this high, and it always dropped back down.

 

Seems like a bad valve

 

idle valve works great.

installs MS2 which controls the valve.

idle valve works poorly.

bad idle valve.

 

Valve had been working for a couple months with the MS2. It just started getting funky the last couple weeks, and went psycho one day.

If there is something in the tune to check, please share.

 

the log shows it solid at 20% duty.

It's possible that 20%DC actually forces the valve completely open. I'm unsure the normal operating value of your valve.

Use output test mode and force the duty cycle of the idle valve to a different value higher than 20%. Check old logs if you can, to make sure that you normally dont idle at a much different DC% and try that number.

If that brings it back down, then you need to adjust your CL idle settings to never allow your valve to hit that particular values again.



IIRC unplugging is not smart as the valve goes into a failsafe mode and open up to ensure the car doesn't stall.


sidenote: I've seen similar happen but it was because D8 remained populated the mainboard, it would cause the zeener diode to clamp down and keep the output grounded.

 

Thanks much, I'll look into that tonight.

 

He did say it started acting weird after a few months.....

 

Recent-old logs (since it was more tuned) look to be around 20. Very old logs (untuned, first installed) look to be more like 40.

 

It is probably driving the valve to the closed balue in response to the high idle. I agree with the previous posts, if you are sure you don't have a vac leak it is probably a bad valve. I assume you have checked the idle screw and throttle plate closure.

Pull the IAC air feed hose and plug the inlet to the IAC.

 

Throttle plate does completely close. I'm not seeing the air feed though, only the coolant hose...unless I'm looking at the wrong thing?

 

What year is the car?

 

2004 msm

 

yeah, just saw that in subject. The google did a particularly poor job of giving me a picture, but it looks to me like they changed the design and shunt the air through the casting as opposed to a hose. Thus, no hose.

You could remove the IAC and ghetto block the air holes with something you have laying around (rubber stoppers?) to see if that does anything for you.

I have cleaned malfunctioning valves of that style before with carb cleaner with success.

 

Thx

 

Replaced IAC and all is well. Thanks guys

 

thanks for posting the solution!