Manager Forum

We've got a real problem child in here today! Im wondering if any of you have any ideas we haven't tried yet. It came in with a MIL, 10 codes in the system. We've resolved about half of them, the other half are all random cylinder misfires and cylinder 4 misfire. We can't feel the misfire and it's only registering on the scan tool at barely above idle RPMs. Client states he changed the plugs himself 2 years ago for the same cylinder 4 misfire. We checked the plugs, they are Champions at gap .064, new is .044 on those. Chrysler calls out NGKs as the OEM plug (Really??). We moved the plugs around, misfire didn't chase them. Moved the coils around, misfire didn't chase them. Got hits on Identifix for fuel injector service, performed service, still misfiring. Checked cam and crank wave forms, all are good even during the misfire situation. We are wondering if it is an injector issue itself at this point. Certainly is a head scratch-er, we don't do many injectors here it seems a rarity.

Valve problems are common on those engines. The early 3.7 had keeper problems that kept the valves from rotating. I'd do a compression test and a leak down test, especially number 4.

Have you checked compression and running compression? Also what about fuel trims and maf ? Id look for vacuum leaks also.

Tech has checked MAF no issues seen, no vacuum leaks detected, fuel trims are all within spec. Compression test came back good, running test and leak down we can't do due to not having the proper tools apparently.

I have had a few with the valve seats dropped out. Maybe do a cylinder leak down test?

Id suspect internals

We are getting a leak down kit, will keep everyone posted with results. Thanks for the help everyone!

Another issue we have seen in the past was valves that were tight in the guide as well as weak valve springs.