02 Chev Silverado 5.3L / No power/Engine light on

[Big Buck Buster]

OK, I have got a good one for you.

Customer complaint: Can't get my truck up over 45 mph, and the check engine light is on.

Scanned the codes: PO300 misfires detected

MAF sensor low

Evaporative emissions fault

Checked misfire data: Cylinders 2,4,6,8 have misfires and 1,3,5,7 have minimal

Watched misfire data: Cylinders 2,4,6,8 count up continuosly, while 1,3,5,7 have 0, or sometimes 1-3.

Checked spark,injector pulse: Both good

Checked plugs: Little brown/Not wet on 2,4,6,8 Black on 1,3,5,7

Checked fuel pressure reg: Not leaking

Checked fuel pressure/volume: within spec

Checked compression on 2,4,6,8: All at 160psi on three hits

Scratch my head for a little bit.

Doesn't make any sense.

Checked for vacuum leaks: none found!

Did a injector balance test on all 8 injectors: All have same amount of fuel pressure drop when activated with scanner.

Have any ideas???

[Esox_Magnum]

Converter plugged?

[KTapper]

Converter plugged?

I was going to say the same thing.

[Big Buck Buster]

I forgot to add that the O2 sensors were working properly.

Unplugged both of them, and no change.

Right on gentlemen!!

After taking the temp readings of the exhaust before the cat, and after, that is what it ended up being.

I should have posted it a little earlier to see how many would take a guess at it.

[Jeremy airjer W]

The giveaway is the one bank missfiring. Along with the symptoms almost always a plugged cat.

You can also pull the upstream O2 and do a backpressure test. I made my adapter out of an old spark plug out of a chrysler. I'll have to post a pic sometime.

[Big Buck Buster]

I did have one a while back that had similar symptoms that ended up being that banks O2 sensor.

That is where it stumped me a little when the O2 readings were going from rich to lean on both banks, and when the bank2 O2 was disconnected, it didn't change it at all.

That is when I took the temp reading on the exhaust by the cat. Took the O2 sensor out of the pipe, and it all went away.

The customers are trying to decide what to do with the truck right now. There are other problems with it, so they are deciding weather or not to even fix the truck.

[Jeremy airjer W]

I have had pretty good luck with the walker direct fits......fitting ! Haven't had any problems with them and saved our customers a little cash at the same time. Might be worth looking into if you haven't to try to get the sale.

[Jeremy airjer W]

The O2's have gone both ways for myself. Stuck rich, stuck lean, one bank, both banks, and all kinds of funky driveabilty problems related to them. I remember reading a "moderators" post on another online auto forum that said something to the effect that an O2 won't cause enough fuel compensation to affect driveablity. WHAT! This guy abviously never worked on any GM's!! lol