Misfires after installing used heads
The truck had a coolant leak and it ran well with no codes. The shop replaced the head gaskets but some of the bolts broke in the cylinder heads, so the shop installed used heads. Now the engine runs rough with misfires and no misfire codes. With the engine running, the Misfire scan data PIDS shows zero misfires in all cylinders, with the engine running and brake torques. The engine only has one cmp sensor in the left head and the engine does not have VCT. I'm trying to figure out what they did wrong?
In the first Gif with the PSD file is the COP 1 in CH A, CH B is the FLSI, CH C is the COP amps with some of the COPs disconnected and CH D is the relative compression. The injectors are all disconnected.
The firing order is … and the COP 1 fires on cyl 1 and cyl 6 while cranking.
The second PSD file with the GIF file is CH A COP 1, CH B is the WPS500 in cylinder 1, CH C is the COP amps, with the firing order and CH D is the relative compression. It looks like only the right bank cylinders 1, 3, 2, 4 have compression, but, in fact ALL 8 cylinders have cranking compression?
The third Gif, with the PSD file, is COP5 in CH A, CH B is ckp, CH C is cmp. The cmp, ckp sync is good, in the left bank, compared to a known good cmp, ckp waveform in IATN.
It is a little hard to use the captures you have here because you mix signals while cancelling important data for it.. 1- I you want to find the "misfire", then use a FLS on the exhaust while cranking with fuel disable and a sync to a cop. 2- After you find if a cyl is actually misfiring then you do a in cylinder compression to see if valve issue or timing, I will try to aid the diagnosis with a…
In this capture, CH A is COP 1, CH B IS FLSE with repeating low pressure drops, CH C is COP amps, CH D starter amps
Have you done a in cylinder test on bank 2? What are the fuel trims at idle and under load?
All cylinders on bank 2 have compression. There are lean codes for both banks.
Several years ago, I had an Isuzu V6 engine with these same symptoms. The problem was, two cylinders were coming up on compression at the same time. Can you make one more scope capture. Trigger from #1 ignition, amp clamp the starter current to get relative compression & get FLS from the intake manifold. This sure looks like you have an 8 piston engine which is running as a 4 cylinder.
Thank you Albin! I believe I also have two cylinders coming up on compression at the same time! My first post has a GIF/PSD file with Trigger from #1 ignition CH A, CH D is an amp clamp is on the starter current and CH B is the FLS is on the intake manifold
Had a ford i installed timing chain 180 off on 1 bank and ran like that 2 cyliders compression at the same time. Scratched my head for a bit on that one till i slept on it and realized what happened. Pulled engine back out and corrected timing and ran great after.
Thanks Robert, I think the chain is off on bank 1 and 2 cylinders have compression at the same time
why do you have 2 spark events on the 720 degrees rotation I mean compare to incylinder pressure transducer waveform I see on the 360 a spark event on cop system?? obviously 3 humps on relative comprecion, on ids or any sacnner you do not see on power balance test any misfire or mode 6?
Engine Crank/Engine Running During engine crank the PCM fires 2 spark plugs simultaneously. Of the 2 plugs simultaneously fired one will be under compression the other will be on the exhaust stroke. Both plugs fire until camshaft position is identified by a successful camshaft position (CMP) sensor signal. Once camshaft position is identified only the cylinder under compression is fired.
FWIW I second what Robert said. I’ve worked on a ton of these engines and years ago I set one of the chains 180 degrees off and had very similar symptoms. I would look in that direction honestly. Hope that helps.
Thank you Thomas, I told the shop to recheck the chains on the cams.