Thread: Vacuum leak help

My fuel trims have always run high in the impala, around 7-13 while driving around town and sometimes up to 15 while idle. When I turn my ac on they go up to 16.4 and stay there. I had p0170, or whatever the vac leak code is, come once last week, I cleared it, removed my evap, replaced all the vac lines with rubber ones, the code hasn't come back but nothing else has changed. It doesn't stall out and it doesn't run rough just sucks in a lot of air. I've sprayed brake clean, didn't have carb cleaner, all around and nothing has changed. Only thing that's been replaced on the motor is the throttle body, replaced with a stage 1 ported, but I had this problem before too.

My k&n intake I can hear sucking air in like crazy, like when I start the car for the first time in the morning, when I'm accelerating. I'm thinking the MAF might be bad and not actually a vac leak. I have a new o2 on the way.

The lim gaskets haven't been done on this motor either so maybe there?

I want to tune but the car is mostly stock and I want to fix this first.

So the p0171 came back today. sitting at the red light my ltft are 16.4, car is not struggling or anything though. When the light turns green my ltft will go down to like 8 if I stay on it but will go back up to 15-16.4 when I let off the peddle.

What do you guys think the cause could be? I don't believe it's a vac leak since it doesn't run rough.

sounds just like a vac leak really.

Figured it out today. Did a smoke test with a buddy, not leaks. Unplugged the maf (should've done that a week ago) and the fuels dropped to where they are supposed to be. Drove home with it unplugged and all was good! Gunna put in the spare I have otherwise just get a new one.

Anything wrong with the hitachi mafs? Can get them for $80 on Amazon.

oem junk yard mafs are the cheapest route to go. im on a used maf for the last 6 years now. best 40 bucks i ever spent lol

Well it's not the maf... Took a test ride and it all went back the same with the spare maf. Gunna do the lim gaskets. Gen V here we come

Coolant plugs on the lim are 1/4" npt right?

yes, I'm doing two LIMs right now lol

what also works is if you have a buddy that vapes...lol

I just read Bill's how to mod a lim again and yup it's 1/4

I have stock injectors, stock table, did touch any of the injector tables. I do have new injectors on the way because they are old and I don't know how dirty.

Haven't done a maf tune and I'm running a stage 1 zzp tb. I know the lim has leaks