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-   -   Bad MAF? (http://legacygt.com/forums/showthread.php?t=154130)

Nochance 01-23-2011 10:54 AM

Bad MAF?
 
I've got a 2005 GT Limited, stage 2. One engine code is because I'm missing a sensor, the other is because of the MAF. I think like 1102, 1013 or something like that, didn't right them down. Anyways, the car starts up but idles really rough and stalls unless I give it a lot of gas then it's ok. I unplugged the MAF and the car runs like new. The sensor doesn't look dirty.

Think it's a bad MAF?

John M 01-23-2011 12:23 PM

If you unplug the MAF and the car runs well, it means there's a leak. There's a small chance that the MAF sensor itself is bad but the odds are 99.99% that it's a leak.

Since it affects idle I'll put my money on a vacuum hose. Check the notorious T under the intercooler and all the other vac hoses you can find. You may be able to hear the leak while the engine idles.

The Murdocta 03-02-2011 03:28 PM

My friend has a similar problem with his.

At stage 2 with the MAF sensor plugged in, the car will start and instantly stall.

When you unplug the MAF it will run, but really crappy.

We put it down to Stage 1 for the time being and it seems to run but only with the MAF unplugged.

Another thing we can notice is that when you get on the throttle there is a ridiculous amount of "whooosh" noise like hes boosting at 30psi but doesn't get past like 10 psi on his gauge.

He brought it to the Dealer who tightened small leaks in the Up and Down pipe and around the turbo as well as some "clamps". Needless to say after $570 of work, the problem is not fixed and were not really sure where to go.

It could be the VAC hoses but im not even sure where they are all located.

Any ideas?

PearlBlueGT 03-03-2011 06:30 PM

I would think you should be able to check it with multimeter (resistance) I can't find what specs range it should be.

madcatz 03-03-2011 08:42 PM

Did you install the maf backwards?

Nochance 06-23-2011 04:14 PM

Since the post, the problem subsided. But earlier this week it reared it's ugly head again.

CEL keeps throwing a P0171 code.

The car runs rough at idle, fluctuating RPMS, sounds like it's trying to leave the hood.

I unplugged the MAF, set off a CEL, but the can runs smooth as silk. I plugged it back in, and it starts rough idling again. I purchased the MAF cleaner a few months back, but it's been a temporary fix.

I'm bringing it to my mechanic tomorrow and have him test for leaks.

sigmafour 06-27-2011 03:44 PM

Today I had exactly the same error code and car is running very rough... I cleaned the MAF, pulled the cable and ran the car with MAF disconnected and then moved on to looking for vacuum leaks... a can of starter fluid and spray around suspect areas and if you hear the revs rise you're getting close... I found a hose that had come off using this technique... I suspect this was it all along but my CEL is still on because I played around with the MAF and need to either clear the ECU by removing the battery or wait for a few starts to see if it catches up... HOPEFULLY I haven't gone and busted the MAF by cleaning it... <shrugs>

Nochance 06-28-2011 08:24 AM

Usually after a few starts with the MAF plugged in the CEL goes away. It did with mine. I got side tracked, and I'm bringing the car in tomorrow. When will it end. :redface:

rollo 06-29-2011 04:31 PM

I've been getting P0171s (lean condition) for a while, only at very low idle though, and because it was circumstantial (and because all my other cars are in pieces and I need something to drive) I've been lazy and just drove it, thinking I'd get around to fixing it soon enough. The idle seemed a bit lower than it should be, but recently it got worse, and the car is stumbling to the point where it's throwing P301, 302, 303 and 304 (misfire for each cyl). It's fine on throttle, but the gas mileage does seem to have got even worse than usual.

Now I think about it, I'm also getting the crazy "woosh" sound, much more than it should be.. I was thinking it's time for O2 sensors (it has 83k on it) but first I guess it's time to check the MAF and vac lines.

Since a lean condition = too much air/not enough fuel, I guess a small vacuum leak could well cause that at idle when the engine needs the least air.

The car is stock except for an exhaust. I'll let you guys know what I find.

sigmafour 06-29-2011 05:58 PM

the vacuum line that caused my P0171 (and for kicks I pulled it off again and the code came back fairly promptly!) was tiny but had a hell of a suck on it while it was off! I think the boost pressure blew it off in the first place.

It definitely doesn't take much of a leak to upset the idle and cause all kinds of rough engine issues... and yes, after a few starts with the MAF reconnected the CEL went out and all started to behave again so I cleaned it for nothing but it was grubby so all for the best...

bmx045 06-30-2011 07:02 AM

This is why a boost leak test can be extremely valuable.

Nochance 06-30-2011 01:26 PM

Sprayed around, nothing. Tested with an identical MAF, no improvement.

Only thing left I have to do is check under the TMIC. I'm borrowing a set of tools tomorrow. Is this easy for a person that doesn't know squat? Looks like basic assembly, nothing outrageous. Is there a diagram, highlighting where to check?

My mechanic is on vacation and wont be back until after the 4th. In to the unknown I go. :eek:

bmx045 06-30-2011 01:48 PM

it's not difficult, 3 12mm bolts and 2 hose clamps, and it comes right out, reinstall in the reverse fashion. put a shop towel in the turbo so nothing falls in it while the IC is off :lol:

madcatz 06-30-2011 02:23 PM

http://legacygt.com/forums/showthrea...eo-164769.html

is your idle something like mine?

have you checked the TMIC to TB Hose?

Nochance 07-01-2011 01:10 AM

Ill have to check the video when I get home. But its got to be the same issue. IC comes off tomorrow.


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