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Iac & maf

09-06-2010, 11:32 PM
What are the best ways to tell which one or both are going bad or are bad?
Signs, symptoms, & testing?

09-07-2010, 11:51 PM
Direct copy of a post I have on 3si for testing the IAC

You can test it while on the car.

All you need is a multimeter.

Test the continuity across the pins. There will be six pins, 3 in each row.


Test continuity across pins 1 and 2, pins 2 and 3, pins 4 and 5, and pins 5 and 6.

Continuity should be around 28-33 ohms if its an old style beige ISC.

If you get no continuity between any two pins then the ISC is shot.

If you find out yours is bad you can get one at rockauto.com

More Information for STANDARD MOTOR PRODUCTS AC99 (http://www.rockauto.com/catalog/moreinfo.php?pk=446333) Its part number AC99

09-08-2010, 05:00 PM
That's some great info!

On the MAF, it will run like shit. The idle will be all over the place and it will eventually stall. Your exhaust will really stink too.

09-08-2010, 05:50 PM
Also do a Google ''Symptoms of a bad MAF'', or ''Symptoms of a bad IACT'

Try cleaning connectors, MAF, and IACT with CRC MAF cleaner.

Cold hard start, bad idle, with no DTC's.

Put the pedal to the metal, and see how quick your car reacts.

09-08-2010, 08:26 PM
Very nice info thanks guys. Reason I asked if because my old vr4 had a bad idle when it was hot out and was fine when it was cold. But the one I have now has the problem every now and then but the main thing was the one day it was real hot and the car was running fine and had a small backfire & then died. I tried to restart it and nothing. I let it sit for a min or so and then it fired right up and was fine. after it sat for about 4 hrs it would start and die every time, eventually it then ran and has been perfectly fine ever since. Very odd and confusing. I do have plugs and wires that I am waiting to put on.

Speaking of which what plugs should I use, I know NGK but what type, I'm running about 10psi. I read that that can effect the plug gap and what it should be.....

09-08-2010, 09:37 PM
Coppers are great but will only last about 20,000 miles. You can get Iridium or the factory Platinum and they should last about the same which is upwards of 100,000 miles.

As for gap, somewhere around .35 would be my suggestion.

09-09-2010, 04:42 PM
Gap depends on the application, mods, and model. If you are a NA, .039 is absolutely perfect. If you are a TT then anywhere from .032-.035 will be a good range.

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