Chasing a p0171

[hensleya1]

Hi all--

First post here so greetings to everyone.

I'm driving a '99 GTP which has been throwing a P0171 recently, system too lean on bank 1. Figured it was a fluke so I just cleared the code out, and it comes back every time I start the car up, within 3-5 minutes. In addition to this, the engine bounces around at idle when warm.

I tried first cleaning and replacing the MAF sensor, and thought that fixed the problem because the bouncing at idle disappeared when the MAF was pulled, but the code (and bouncing at idle) came back immediately with the MAF inserted. So, I think it's a new MAF and splurge on the part - no dice.

I changed out the vacuum lines about a month ago so I haven't bothered to check them yet (will likely do so tomorrow or Tuesday), but I monitored the AFR and it never climbed above 14.7:1 at any time driving, but the SES light came on nevertheless - this makes me think the vacuum lines aren't the issue.

Before I throw any more money on parts that may or may not need to be replaced, any thoughts on this?

(I'm thinking it's the O2 sensor.)

[Fivefingerdeathpunch]

Have access to a smoke machine??

Thats the best way to track down a vacuum leak.

Other commom spots are the tb gasket, EGR tube as they can crack or maybe even a supercharger gasket.

The commanded AFR won't change from 14.7 as its always trying to stay at stoich while crusing around.

[dsmuts]

You likely have a vacuum leak somewhere

[hensleya1]

Hi all--

Found the problem, and I started cracking up the minute I noticed it.

The supercharger bypass valve is cracked and the two pieces don't want to hold together - and the previous owner was holding it together with a plastic zip tie, which had popped off. I forced it back in place so it was a snug fit, and all is well again. No more vacuum leaks. LOL

To be sure, new part on order. But still, one for redneck solutions.