EGR or MAF

[corvette66]

OK, well I have been fighting this idle problem for a while now. I decided to change the plugs, plug wires, fuel filter and it really made a big difference.

BUT...I still have an irregular idle. It idles high, low up and down, between 800-and 1300 rpm now. I figure it to be MAF or EGR, I have had both codes show up in the past few months. I have never had the idle speed control sensor code, or a throttle position sensor code, so what do you think? probaly MAF or EGR right? which should i replace first hmmmmmm

thanx

 

[Edmond]

Why not both of them?:L:L:L

The EGR is an item that has an expected life span. If it is the original, I would replace it. They're usually in the $60 neighborhood at your local auto parts store.

I would change that first and see what happens.

Can you visually see anything wrong with the MAF? Do you still have the screens on both ends?

Would you have a K&N and happened to over oil the filter after you washed it? New MAF aren't cheap but I did manage to pick one up for $60 from a Vette' junk yard to remove the screens. Try www.vette2vette.com for your best bet.

 

[wishuwerehere82]

Try Twin Turbo's site for debugging. He has lot's of good info regarding idle surging even though it's not a cross-fire

 

[wishuwerehere82]

Wooops. Here's the link.http://www.crossfire.homeip.net/

 

[corvette66]

thanx for the info guys. i'll check out those sites. READ THIS CRAP below

This is nuts!!! This C4 is drive'n me crazy. So today after I posted this thread , I went out to check and make sure what I said was 100% correct. So i fire it up, let it run for a while. shut it off, and I hear a hiss'n noise from the motor. So I investigate.... sounds like the IAC, so I unplug it, the noise stops, but returns...this time hiss'n from the air pump electronics, so i unplug that too, goes away, then returns at the other air pump plug, so i also unplug that, now it hiss's from TPS. i unplug that, then they all start make'n noise !!!! WTF is go'n on here!!!!!! ad

crazyniss

BTW: i can't see anyhting visually wrong with the MAF. but when i unplug it, the idle changes a good bit. it idles higher, but smoother

 

[wishuwerehere82]

That's not good. With the ignition off, all power should be cut to all input sensors and output devices. Does it sound like a vacuum hissing or an electrical hissing? Sounds like electrical if it's moving around. All these devices are tied into the ECM though the wiring harness, and if the sound moves around and all of them hiss, then the ECM is the most likely culprit. In any case, your TPS is an input sensor and shouldn't have any feedback on it. Wierd!
This might be a good time to reset your ECM and retrain the memory from scratch, in case you have a bad sector stored.
Remove the battery connection for a minute or so, and then restart the engine and let it sit and idle for 5 minutes or so, then take it for a 15 minute trip and put it through all of the normal driving conditions.

 

[corvette66]

Yeah it was an electrical hiss, and the ignition was off. Also I had reset the ECM about 5 minutes prior to this hiss. I wanted to see if I would get any new codes. None came up, but I got a new suprise with this odd hissing problem.

I will def try reset it again. weird huh

 

[wishuwerehere82]

Yes. Very wierd. All I can think of is some sort of oscillation in the voltage regulator going to the ECM.