98 Galant Approx 160K miles. I came to a stop and noticed at idle my RPM was @ 2000rpm. Typical RPM is around 900-1000 RPM at idle both in and out of gear.

After restarting car the check engine light came on and when driving proceeded the car would surge. I removed the air filter since the engine seemed to be surging, and had no change. After I removed the air box from the intake the engine seemed to idle at a steady pace, but still very high. Driving with no air box connected to intake still produced surging and stalling. I decided to hook up air box to intake and unplug the MAF sensor. The car seems to drive fairly normal with slight (100 rpm) movement at idle. when in park the RPM goes up to 2000.

I removed the MAF and cleaned it with MAF cleaner spray, as well as the intake throttle body and all connectors. The idle RPM dropped to 2000, and the Drive (in gear) moved to 1100. After unplugging the MAF the car seems to lower RPM's to near normal and run better.

Would it be safe to say the MAF is bad? I just hate to replace for $250.00 and find out it is the Idle controller. Though it seems logical that if the car performs better with the MAF disconnected, it's the MAF.

What do you guys think?

-Corey-

 

Did you get the check engine light scanned?

 

I didn't yet. I have a friend bringing me a scanner tomorrow (Friday), and hope to scan it after work to get the codes.

Plan is to hook up MAF, Clear all codes, and then let the check light come on again. I will report back with code once I get it.

Any other replies in the mean time would be appreciated.

 

You should scan it before you replace any parts.

 

Yeah, I decided while at the parts counter last night to wait until I scan it and see what you all think. From what I understand it's possible that it's the IAC, and both parts are a bit of money.

Will post scan codes ASAP

Thanks for your help.

 

I hooked everything back up (including MAF) and cleared all codes. The only code now displaying is P0505 "idle control system malfunction".

So I am assuming the iac is bad?
Why would it run better with maf unplugged?
Iritis is the iac? Is there anything to clean to possily restore function or is it just a straight replace?

Thanks for info!

 

Idk why it would run better, try checking for vacuum leaks, a stuck pcv valve and test the coils on the iac.

 

I took the pcv valve and tube and cleaned it out with throttle body cleaner, so I assume it should be doing it's job. I read somewhere that when the maf is unplugged the car goes to a default idle table and that's maybe why it runs better then plugged in?

I will have to check the coils, honestly I have never done that, but I think I found a good tutorial. Does this look accurate? or is there a better tutorial for these cars?
http://dmtalon.v8eaters.com/ISC.html