Question about LTFT

[Dirktdolman]

I have been chasing a P0300 random misfire. So the other day I used the PID list from the Calc.VET. After capturing the log I ran it and noticed the Bank 1 and Bank 2 LTFT were different. It was my understanding Bank 1 was one side of the motor and Bank 2 was the other side. If that is the case I would think they both should be close if not the same. Bank 1 was 14. something and Bank 2 was 11.4 about. This would lead me to believe I have a lean condition going on which might be causing my misfire. Any Ideas?

I have a 03 Silverado LQ4 4L80 4 X 4.

LS1B_0196.efi

[joecar]

B1 is different than B2 only by a few percent, this is ok and is not necessarily...

the problem is that they are both significantly away from zero, they are adding more than 10% fuel...

since they are not pegging, they are able to maintain trim,so this is not the reason for the misfire...

but two questions remain:
- why are they not within 5% (or less) of zero...?
- what is causing the misfire...?

[joecar]

From your log, I noticed that when you open throttle (to say 75%), MAP increases, but MAF barely climbs (does not go above 130 g/s), and RPM stays almost the same...

this leads me to think your air filter is clogged.

[Dirktdolman]

I will check it but it it is not does that mean there might be a problem with the MAF? I had an oil pressure sender go bad (direct short the signal voltage) this summer and it all but shut the truck down. They thought there might be something wrong with the MAF at that time.

[joecar]

Yes, it could be the MAF itself.

Also check the MAF plumbing (loose or collapsed).

[Dirktdolman]

Plumbing is good.

Is there a good way to test the MAF itself?

[Dirktdolman]

I forgot to mention the P0300 only happens on deceleration. Normally I would think this means a vacuum leak. I have had a evap leak test completed but I do not know if they checked the manifold for leaks.

[joecar]

Plumbing is good.

Is there a good way to test the MAF itself?

At WOT, as engine spins past 5000 rpm, MAF should be reading 275 g/s or mor.

[joecar]

I forgot to mention the P0300 only happens on deceleration. Normally I would think this means a vacuum leak. I have had a evap leak test completed but I do not know if they checked the manifold for leaks.

Do a CASE Relearn, and see if the misfire DTC still occurs.

[Dirktdolman]

I will give both a check and see, Thank You.