Gos2Slo

Ok, I've been fighting this "poor running" condition for almost a week now. The car starts and idles fine (a little rough idle sometimes, but not bad.) I can rev it in park and it revs up just fine, all the way to 6 grand.

If I try to rev it in gear, it coughs, sputters, and won't rev over 3K rpm. After a minute of driving I get a code 171. I earlier had codes 303 and 307, but I checked the injector harness, plugs and wires and all appear to be fine ( the plugs look a little black (soot) but otherwise fine.

I have a new coil and ICM in it, the MAF seems to be fine (new wiring harness to both the MAF and coil) the opti and o2's are 8 months old, so is the water pump. Fuel pump and filter are a month old each. it doesn't lose any fuel pressure, even after a couple hours.

Any hints? Why is just bank one (drivers side, right?) lean? If it were a vacuum leak wouldn't both sides be lean? help!

CamaroSS30thAnn

i would like to know the same thing....my car runs lean on the same bank ...but im not getting a code....well it runs lean when the car wants to run lol....

Gos2Slo

Just checked the fuel pressure again, it's 42 at idle and 50 when revved, no fuel in the vacuum lline of the regulator and it doesn't bleed down either. So do I have a bank of bad injectors (unlikely as hell) or a spark problem maybe?

I tried bypassing the MSD, no difference.

Wild1

P0303 and P0307 are misfire codes for cylinders 3 & 7. Something is up with those cylinders. Sounds like an intermittant.

Bank 1 lean confirms the misfire. You're on the right track tracing injectors and ignition. Check for any arcing with your spark plug wires.

I went to a loading dock at night and put my front wheels up to the edge. Then start the car and go around to the under end of the loading dock to look under the car. You may see a few intermittant sparks. If you have a buddy, have him/her raise RPMs to 2500 to increase the load on the coils. Check for sparks. Yeah it's a rigged way of checking spark but it beats crawling under a hot engine that is running...

Gos2Slo

I've heard that everything from a vacuum leak, to a bad MAF, to clogged cats can cause this code. I already ruled out the fuel pump/filter, and the cats aqre 45 months old too so I really doubt it's that. I also had a 2 minute period yesterday where the car ran perfectly, and it pulled hard enough to convince me the cats and fuel system are fine.

So does anyone else have a guess or does a dealer need to rape me first?

Injuneer

If you are only getting the "lean" code on one bank, you need to look at things that only affect one bank. Misfires and exhaust leaks are the most typical problems. A bad MAF, FPR, etc. would affect both banks, not just one.

But you have to verify that the problem is only on one bank. The code sets when the PCM has max'd out the BLM on that side at 160. Maybe your BLM's on the other side are running high, but just haven't max'd out and set the code.

Do you have any scan data other than trouble codes?

Gos2Slo

I wish, I get my commission check Monday and am planning on a Scanmaster or something.

I don't hear any exhaust leaks, and the plugs and wires look good. Possibly a bad cat on one side only?

I don't know, Im about at the point where I want the car to sit in my driveway and rot just out of spite. Mature, eh?

I think I'll just bend over and take it to the dealer, I'm tired of chasing problems on this car and want someone with a serious scan tool to have a peek at it.

Wild1

I agree with Injuneer. But since your codes seem to be intermittant with moments of normal operation, that would indicate injectors or ignition. An exhaust leak will throw off the BLMs but would be more of a constant problem.

Hang in there...

Gos2Slo

It's pretty constant, I just think it's weird it revs pretty normally when parked, just not while in gear. I have to drive it each time I fiddle with it to see if it's fixed, because it runs so normally at idle and parked.

Gos2Slo

By the way, what does BLM stand for?

Injuneer

BLM = block learn mutlipleir. Its the "long term" fuel correction, that the PCM stores in memory. It uses the stored number, divided by 128, to multiply the normal fuel requirement and extend the injector pulse width to compensate for a perceived lean condition (when the BLM is over 128) or shorten the pulse width for a perceived rich condition (BLM under 128).

There is a separare BLM for left and right banks of the engine, and 18 different sets of BLM's to cover the full range of engine operating load (MAP) and RPM.

Gos2Slo

Ok, cool, thanks for the info.

I made an appointment at the local Pontiac dealer (the Chevy dealer here is run by a bunch of crooks) for Tuesday, I'll let you all know what they find.

Gos2Slo

Ok, just for grins I went out and popped off the fuel rail, took the injectors out and flushed out the fuel rail, cleaned everything out and put it back together.

No better. Tailpipes and the back of the car are black with soot, so I think it's getting plenty of fuel, just not sparking it for some reason. I wish I had more than a code 171 to work with, but that's all it throws. Oh, and I tested the voltages to the MAF, all is well and fine, right within spec.

Could a vacuum leak be causing this? It would have to be a huge one, right?

Wild1

No, it wouldn't be the MAF, Fuel Rail, or Vacuum as you wouldn't be getting specified misfires... the whole car would have affected BLMs. Your CAT may be toast too! But check your ignition. With the engine running, get under there and have a buddy rev the motor 2000 RPM. Again, a loading dock is pretty good for this test to get under the car. Roll the tires to the edge and chock block the tires, pull the emergency brake, and put the car in Park...

You will see blue sparks where you are getting the misfire.

Cylinder specific symptom. Will cause a rich mixture (black carbonized tailpipes).

Good luck. Save a buck and do this before you take it in. You may be surprised.

Gos2Slo

Ok, I'll throw it on the ramps tonight and see what happens. I've been thinking the cats may be toast too, it's exhibiting a lot of the symptoms that it had the FIRST time the cats had to be replaced.

Can I unbolt the y pipe and take it for a brief spin to see how it drives? Or will it still run terrible with no O2's?

If it's the cats again (and the dealer won't cover it) I'll just buy an O/R pipe. Getting sick of this happening!

Thanks Wild1