1999 Suburban K1500 5.7L 133k miles
I have been tracking down a long standing misfire problem with my suburban and have done many repairs and tests along the way in an attempt to fix. Here is the sequence:
Also don't want to install the new cats until I fully resolve the the new misfires.
I have been tracking down a long standing misfire problem with my suburban and have done many repairs and tests along the way in an attempt to fix. Here is the sequence:
- P0300 and P0306 DTCs appear
- Arbitrarily replaced plugs, wires, disty rotor and cap.
- Compression tested all cylinders - everything looked fine
- Misfires got progressively worse creating blinking MIL - I assume I started seriously damaging my cats
- Replaced fuel filter and CSFI injector with a new MFI injector - introduced intake leak as fuel meter body o-ring didn't seat properly
- Misfires continue
- Performed a leak down test of all cylinders - everything < 6%
- P0430 DTC appeared
- Got a bluetooth OBDII reader and using Car Gauge Pro determined misfires on all cylinders but cyls 6,4,3 were much higher in the thousands, CMP retard too high (4+), LTFT too high (20%+) and B2S2 following B2S1 in closed loop - I evidently destroyed the Bank2 cat.
- Replaced disty, got CMP retard to 0-.1, cam gear was seriously worn - knife edges
- Misfires almost completely resolved - still maybe 1 or 2 on one cyl at high speed, never enough to record in the history. Felt smooth and P030x DTCs were resolved.
- Found intake leak I created in #5 using a smoke test and repaired. LTFT lowered but still too high with 10-15% still being registered.
- Tested fuel pressure, when fuel pump is active it is at 60-62psi but when off settles back to 50psi and is regulated there. That is at least 5psi too low.
- O2 sensors are the originals, so I bought new O2 sensors. I bought new cats but have not installed them yet.
- I replaced only one upstream sensor (B1S1) on the old cat to see if it helped the LTFT; it did lower it, but now misfires have returned, mostly at idle. Still too few to record in the history <10 per MF cycle.
Also don't want to install the new cats until I fully resolve the the new misfires.