2002 T/A

I was out for a flogging and then had to get fuel at not my typical station of known fuel. Then I noticed a loss in power, flashing check engine and P0302 code, cylinder 2 misfire? I pulled the plugs, no arc tracks. Replaced 8 plugs, 8 wires to start fresh. Added octane booster and 3/4 tank of known fuel. I still have a loss in power under load, starting around 3000 rpm, then the flashing check engine? Exhaust note is also off? We put a scanner on it and noticed two things, 1- numerous misfires especially cyl 2 and most of the right bank? 2- fuel trims are minusing, right bank? I find this strange as I would think if its pulling fuel its rich, not lean? So were and why the pinging? Checked the cats with an infra red, temperatures are in the mid to high 300s F, no indication of blockage. Also checked the knock sensor, it was not pulling timing at all? I have no mechanical noise to think valves or broken parts? We also pulled the MAF to check for an obsruction, verified all intercooler ducting and belts? Now I am thinking crank relearn, have to get a proper scanner to do this! Injectors have 10,000 km on them with the S/C install, again, STFT are pulling on the even bank and power down across the board? Thanks in advance for any insight.

jimmyblue

iTrader: (11)

I think I'd put it open loop on the was-good tune
and see what AFR looks like. Maybe do the cylinder
balance tests that your scan tool may have (?) to
see if there's an injector imbalance, like your mystery
gas comes with a free loogey.

gametech

iTrader: (1)

Have you considered that the bad gas could cause pinging AND have contaminants that blocked your #2 injector flow? I remember a situation in San Antonio some years back where the Premium pumps were spewing kerosene.

2002 T/A

Good points from both! My former GM tech buddy who is working on the problem mentioned an injector balance test? He is retired so no access to the equipment to do this, may need to take it to the dealer? As for good fuel, I am still getting the pinging with known good fuel and octane booster in the tank? Still wondering why it would be pulling fuel on STFT if its already lean from a dirty injector(s), as I am getting multiple misfires? Does anyone know anything about crankshaft re-learn? Looks like the code has to be generated before the re-learn can be done? Don't think I stretched a chain but wondering if the flogging threw something out if possible?

jimmyblue

iTrader: (11)

If (say) one injector was sticky and slow to close, its
excess fuel would be pulled back by negative trimming
until the bank average is centered. But that means the
other three would be put lean enough to balance it out.
If hole #2 shoots 20% rich then you'd trim -5% and
get (say) +15, -5, -5, -5 (adding up to 0 bank error)
on the 2, 4, 6, 8. Meaning that now 4, 6, 8 are prone to
ping and misfire any time negative LTFTs are enabled
(i.e. anywhere but WOT open loop).

Not to say this is actually what's going on, just one
thing that could.

Now when you say pinging, you also need to check
whether you get KR or not. You can ping without KR
if it's really dieseling or preignition; KR is for spark
knock that comes after ignition, and sensors have a
blanking applied to make them ignore stuff that isn't
spark induced (since then spark pullback can't fix it).

2002 T/A

Ok, thanks! I was wondering the same about #2 injector partially open due to whatever causing an over rich condition? And yes, it would attempt to lean out the bank to compensate for sure. We did check for KR, no timing was being pulled during the logged misfires. I guess the next thing to do is an injector flush? What are your thoughts on Crank Re Learn? I would have to get access to a Tech 2 and am working on that!

jimmyblue

iTrader: (11)

Crank relearn can be done with some aftermarket scan
tools, but in my experience this "comes and goes" as
far as functionality and is a PITA even when working.
A pretty fussy and poorly explained process. But it
is also unnecessary outside of things like cam swaps.
Misfire detection is the primary purpose of crank learn.
But anomalous (like 1-2 cylinders staying "out of bed"
with the rest of them rattling around at 0-2 counts)
points more to some imbalance of fuel, air, spark (and
air can probably be assumed uniform other than valve
train issues).

2002 T/A

Got it, thanks! Just found out from another GM tech that there is a bulletin out for the P0302 code I got, Cylinder 2 misfire. This was my first symptom following loss of power. Turns out that there is a known issue with the F-body for A/C condensate dripping on the right bank O2 sensor causing corrosion. My mv were hovering around 750/800, a little high, but didn't really catch the eye as we were looking for misfires. GM says to swap O2 sensors and see if the problem manifests on the other bank? I am waiting for a spot on the hoist as it could get nasty removing them? We also want to do an injector balance and flush if need be. Has anyone come across this?

kingtal0n

iTrader: (1)

The first thing I would do whenever I think I have a misfire without obvious culprit is a compression test. since they are relatively free, quick and offer exclusive insight about the engine that no other tool really comes close to offering for that price.

2002 T/A

Well, after interchanging 02 sensors, plugs, coils and injectors bank to bank. Checking valve action and compression, verifying fuel delivery and pressure, the only thing left is a back pressure test! Right bank cat had a 2 psi pressure drop @ 3000 rpm. The first thing I checked was the cats at a muffler shop with an infrared, they were fine? Took it to a GM dealer, the guage dosen't lie! Also verified the left bank for comparison. New cat installed and power is back :-) Now that I know nothing is broken, I am putting her up for sale in the spring, bought a Cadillac. Hope this helps someone else out, thanks for the input :-)

joecar

So bank1 cat was clogged...?

2002 T/A

Cat was fine on bank 1, 0psi pd. bank 2 was 2psi pd @ 3,000 rpm.

joecar

Ah, I got my left/right confused.