Hello folks,

Having some issues with the SS lately. Hoping someone can point me in the right direction.

I first got the P0171 code about a year ago. Bought some MAF sensor cleaner, cleaned it up real good, CEL went away for about 2 weeks. Figuring I didn't clean the MAF good enough, I took it back out, sprayed it out really well, let it dry, and put it back in. CEL went off this time for about 6-7 months. Come February, it came on again as I was pulling out of the parking lot of the dealership after having the annual safety and emissions inspection done. Figuring it was the MAF and that I'd get a new one as soon as I financially could, I didn't bother cleaning the MAF again and just let it go. I was not having any driving issues, performance issues that I could tell (I don't really get into the pedal very often), and certainly no stalling/rough idle.

Last weekend, I started my car after driving quite a distance after a quick stop to pick up something to drink, and was greeted by a really rough idle. My car usually idles around 700 in park,but on this instance it was chugging and loping around 150 - 200, shooting up to about 1000, dropping back down to 200, repeat. I goosed the gas pedal, and it continued to do this. I shut it off, and started again, problem went away.

Knowing that one of the other causes of P0171 is possibly an injector, I stopped at Autozone and got a bottle of STP fuel injector cleaner, and dumped it on top of a 3/4 full tank of 93. Didn't have the issue again, until the next day when I went to Goodyear to have my tires balanced and rotated.

I go in, tell them what I want done, sign the paper, and hand over my keys. He tells me they'll pull it right in, and I go and sit to wait. Not 5 minutes later, the guy comes in and says "Hey man, do you know about the check engine light and the car running rough and all that?" Thinking that he'* trying to sell me a service, I told him I was aware of the check engine light, and knew what it was, and just wanted my tires rotated. He says, "no man, it died on me twice in the parking lot. We're not going to work on it, there'* obviously more important stuff going on than needing your tires balanced. That engine might be what'* causing your wobble at 60-70 mph." WTF, Over?

Anyways, I go get my car, too mad already due to the heat and my AC being broke to deal with these people, and leave. My car starts fine. I pull out of the parking lot, and up to a red light, and the idling thing starts again. I give it some gas, it seems ok, then starts chugging while I'm halfway through the intersection. Kind of like it'* not getting enough fuel. I'm pushing the pedal, but the RPM is bouncing like crazy between 200-1000, and finally it stalls in the middle of the intersection. I get it to the side of the road, and start it, it starts fine, then goes into a regular idle for about 10 seconds, then starts the rough idle again, and dies. I let it sit for a minute, start it up, and push the pedal a few times taking the tach up to 4000 and letting it fall back down, and now it'* idling fine. I drive about 4 - 5 miles to autozone, to have it scanned again, wondering if maybe they can pull a history or whatever with their tool. The car does fine, no problems whatsoever, the idle problem gone.

I was finally able to get the code scanned, and lo and behold, it'* not P0171, it'* actually P0134 and P0135. Bank 1 O2 sensor. I bought the bosch part (I now know I shouldn't have from learning this on an Impala specific forum, and will be replacing it with an AC delco part in 2 weeks), replaced it, drove for a little bit, and my light went off. Woohoo! I also changed the PCV while I was under there.

Three days later, after going about 3/4 throttle to pass another vehicle, I was greeted once again with my lovely little orange driving partner in the dash.

Another scan indicated P0135 again, P0134 again, and back from the dead, P0171.

Finally I had some time to work on the car today. I was originally going to gut my airbox today, but with my car already running lean, I don't want to worsen the issue by improving airflow.

I was able to finally change my fuel filter after quite some time. Some PB blaster and vise grips on the rounded fuel line nut popped that sucker right off. I suppose it was time to change it, as the fuel that came out of the old filter was blackish in color.

I unplugged the MAF sensor and ran the car for awhile. I'm not sure what I was supposed to be looking for here. My car did idle funny after unplugging it, bouncing between 800 and 1000 RPM. It did not want to stall out or anything though. A couple of runs down the road and back, and HOLY CRAP. I'm not sure what unplugging the MAF did, but my acceleration opened up like crazy from 35-70mph before I let off the throttle.

I checked over all the wiring to and from the O2 sensor, MAF, etc. All wiring and harnesses check out ok with no fraying, cuts, melting, loose connections, etc. The battery terminals and posts are clean.

I swung into Autozone to have the car scanned again, and sure enough, I was throwing P0120 due to the unplugged MAF, but the P0134 and P0135 codes are gone, but the P0171 remains, telling me I'm still running lean.

In looking over the engine bay, listening and searching for vacuum leaks, I was unable to find anything. I thought I read to spray throttle body cleaner around the vacuum lines to check for leaks, but there'* two problems with this: I don't know where all the vacuum lines are, and after reading the warnings on the bottle of throttle body cleaner, I was unsure if I should proceed with this as it said to NOT use it on cars with a SC.

The only think I could find that I thought was a vacuum leak was the whistling/whooshing sound coming out of the open tube below on top of my blower. The tube looks as if it'* been cut. I did not cut it. Should this be connected somewhere? If I put my finger over the hole, the car starts to stall.



So, I'm unsure how to proceed at this point to get rid of the P0171 lean condition. The car seems like it'* running great, I don't hear any knocking or pinging, and the only way I can induce the strange idle is to unplug the MAF. This doesn't reproduce my original problems though, as that idle was a rough idle that bounced as low as 150-200 and up to 1000 RPM. It has not stalled since when I first posted this issue either.


One of the fixes listed for P0171 is injectors. Is there a way to check each injector myself? Are the injectors something that should be changed all at once or will changing one, if I find that there is one with a problem, ok? In looking at them, I can't really figure out how they come out. It doesn't look like they screw in, but I can't tell.


The car has ~87k miles on it. Last oil change was about 1500 miles ago, Castrol full synthetic 5w30 with a K&N filter. I'm running a K&N air filter that was last cleaned about 10k miles ago. I've never changed plugs or wires. The car does have new lower intake gaskets as of about 2-3 years ago, and a new right valve cover gasket changed at the same time.

Loud

Looks like he'* turning blue. Quick, get an O2 mask on him!!!

From the first 2 paragraphs I knew you had a MAF issue. When unplugged, the PCM reverts to a pre-determined set of values based on cylinder air mass rpm etc etc.

Replace the MAF sensor. Then we can work on the rest.

I can't replace the MAF until 2 weeks from now. The AC delco part is $204 at rockauto and I just don't have that right now, and I don't want a reconditioned one due to bad reputations. I also don't want a used one.

Regarding the vacuum leak, from talking to a Guy on another forum, he seems to think I should plug the tube and reset the PCM, due to it learning the leak and adjusting for it. I just can't understand why it wants to die when I put my finger over the tube.


Loud

I can't edit my old post to add this, so sorry for the double post.

Here'* a pic close up of the tube. It doesn't appear to have had any cap, plug, or stopper in it at any point. It actually looks like it was cut, but I can't find the other end anywhere.

Im hesitant to plug it because of how it acts when I put my finger over it. I don't hold my finger on there long because I don't know if its hurting it, so I don't know if it will actually cut off or recover.

Loud

That broken tube goes to your HVAC system. Its what controls the door vents. The tube might have fallen down below your fuel lines. You can plug it for now. Thats a huge vacuum leak you have.

You should be fine driving it with the MAF disconnected. It might hurt your MPG for abit.

I thought I had found something about that too, but then found a post on a grand prix forum explaining that the 04 and 05 impalas use an electric blower door instead of a vacuum operated one. Plus my vents/doors operate fine. That post said it should be plugged too. Im just really hesitant to plug it up because of how the car runs when I cover it with my finger.

Loud

Ok, I was thinking of the Bonnevilles and the vacuum actuated doors. With that said, plug that line with something. A screw, booger, or whatever that will fit in it, but won't get sucked in. Yes, the PCM is compensating for the active vacuum leak, when you put your finger on it, it takes the PCM a few seconds to re-compensate again.

Ok, lets start over. Plug that line with something. Plug your MAF sensor back in and restart the car. Let us know what you find.

Leak is plugged. I used a 1/4 x 1/2" long large head screw to put in the hole, with a vinyl cap over that from the end of my new fuel filter. Its all I had on hand at the moment.

If the attachment works, this is a video of my car at idle with some revs. Anything sound funny to you? That tapping is concerning me, but I may be spooking myself. It seems like its coming from the injectors, which are in the heads, which is where the valves are. Sounds sort of like valves tapping.

I still can't edit my post for some reason. Here is a link to the video. Hopefully it works.

http://s40.photobucket.com/albums/e2...528_205255.mp4

Loud

Did you plug the MAF sensor back in also?

Sounds like your injectors. Otherwise it seems to idle fine. Go drive it around and see if the engine light goes away. Or have it cleared.

The edit feature is turned off. We would rather have you add another post, than edit something and it not be noticed. So don't worry about adding all these posts. lol.