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350rs 12-27-2009 12:42 PM

junkyard MAF solves problem?
I put a junkyard MAF on my GT from a 3.1 lumina. ( Same part numbers) I havent had the high idle at start from a day or two after. But i figure thats just the computer relearning everything in a way. NOW, however, i sometimes have a high idle when i have a warm startup.. Like im doing a bunch of short stop running. Come out of the store 15 or 20 mins later and it has cooled a bit. It wants to run high then, and turning it off and on dosent fix it as often.

But on a side note.. i did start running mid grade fuel in it. ( yes yes i know " it wont help",, but it has..) Im not going to say i get a noticeable performance upgrade or better mileage. But it is OVERALL doing better. Could that be coincidence with the new MAF? Sure it could, but ive only been using the mid grade for a few weeks the the MAF has been on for a few months now.

AaronGTR 12-28-2009 11:49 AM

If the old MAF was dirty or somehow otherwise damaged, and wasn't cleanable/fixable, then putting a new MAF on could certainly help. Doesn't matter if it was used, as long as it's functioning properly and it's the same part. It might affect your fuel trims and should make the fueling more accurate and improve your mileage a bit, but it shouldn't really affect your idle speed. I know sometimes a dirty MAF can cause a surging or rough idle, but that should be from inaccurate fuel metering at low engine speed. The idle is usually set just by coolant temp (warm or cold start), the TPS sensor, and the IAC valve. If you have a sticky or dirty throttle plate or IAC valve that could be affecting idle speed, or possibly if you need to do a throttle position learn procedure. You'd need someone with a scanner to see what number the pcm is seeing with the throttle closed and open, but you could do the procedure regardless just to make sure it is ready correctly. Not sure what else it might be.

350rs 12-28-2009 09:12 PM

my old one didnt appear damaged. and i cleaned it over a dozen times. It may have had NOTHING at all to do with my problems. But ive changed every other sensor or thing of the sort that it coulda been. IAC, throttle position, IAT, im sure there are others somewhere. Only other thing i can think of is the EGR. Its totally computer controlled right? I dont remember seeing a vac line off of it? Correct me if im wrong though.

AaronGTR 12-29-2009 06:37 AM

Yeah, the EGR valve is completely electronically controlled.

350rs 12-29-2009 02:54 PM

i guess that could technically be it. If turning off and on helps it. Even though it wouldnt really make since. Took it apart not too long ago and all looked fine. Stuck my finger in the passage and came out black, but not overly black or chunky. EGR held a bit of pressure but just my lungs could make a slight leak. But very small. That was blowing though, not sucking.. ( let the jokes begin..) Is this system a pressure or a vacuum?

AaronGTR 12-29-2009 11:03 PM

In a normally aspirated car it has vacuum in the manifold and slight pressure in the exhaust. It is normally only open a little at idle, opens more at light throttle, and closes during heavy throttle. I don't if it would really affect your idle speed much or not.

350rs 12-30-2009 09:34 AM

i dont either. but im almost out of options. ill spray for a vac leak somewhere again. Are there common areas for those on these cars?

DoCDooM 01-02-2010 10:49 AM

On a side note, I was at a junk yard last year looking for some "stuff" and opened up the driver's door on a wreck.
Know what I found? About a half dozen MAF sensors on the seat, all taken apart, all totally trashed.
Someone from a dealership had gone through the entire yard and wrecked every last one of them.
Fawkin GM.

AaronGTR 01-02-2010 04:12 PM

Heh, well no one seems to want MAF sensors anyway. I've had one for sale for months on this forum and on ebay and no one has bought it.

westerndragon 01-02-2010 04:51 PM

i have a periodic high idle sometimes at start sometimes while running turning the car on and off usually fixes it i belive mine is from a leaky LIM check for coolant

350rs 01-02-2010 08:26 PM

thats not it. Ive had it and fixed it already. Coolant stays where its at. and nothing in oil. Im good with that.

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