The Unfixable Misfire
Hello everyone! I hope this one is beneficial! The vehicle is a 2003 Ram 2500 5.7 (D). VIN: 3D7KA26D63G719786. Complaint is: Misfire is still present after the spark plugs, wires, have been replaced and coils were tried, but still has the misfire, so the coils were taken back off.
It came to me to find out why it was still having the same problem. Nate ( my technician) connected a scan tool, and test drove the truck. He came back, opened the door, showing me it only had P0300, I asked him to look at the generic side to see if he could get more information.
Shortly he came up and said that he was getting equal counts on cylinders 1, 2, 3, and 4 with no counts on the other cylinders. Firing order is …, odd cylinders on the driver side bank, even on the passenger side.
I decided to look at two cylinders on bank two, one that was supposed to be misfiring, and one that wasn't, attached are two screen captures of cylinder 2 (misfiring) yellow trace, one showing cylinder 6 (not misfiring).
Immediately, it was evident that cylinder 2 has what appears to me to be a valve problem, then to be thorough, I checked other cylinders that were identified in counters as misfiring, compared to not misfiring cylinders, only cylinder two is having issues.
The valve cover is easy to get off, so Nate removed it for a visual, and there it is! A broken intake valve spring. This whole analysis took 45 minutes, even with checking multiple cylinders and valve cover removal.
Rusty nice job...we have done many of those Hemi's. The most common cylinders that we found are number 5 and 7 followed by 6. The cams wear out especially if they use cheap oil. Be carful and make sure you can get the lifters especially if its a MDS (cylinder cut out). We have also experienced the camshaft having to much end play and the cam bore where the bearings would normally go being
Thank you G! Happy New Year! This one just has a broken valve spring.
Not going this year G, hopefully I will see you sometime soon somewhere
Man, Rusty, you have good luck! We had a Jeep 5.7 come in for freeze plugs. After the work, the engine was filled with coolant, and was running to cycle the fans. One of the valves stuck....and bent....while idling in the shop. That was fun to explain. Not!
What probes are you using, and why did you start with bank two? Seems like dumb luck that it was the first place you looked, so you must have left something out. (?) These Dodge 3.7, 4.7, 5.7 are at the point where the only reason it comes to the shop is a valve problem. The Craigslist mechanics do the "tune-up" before the owners take the truck to a real shop around here.
The misfire counters indicated 123&4 misfiring at the same rate, cylinders on bank two were most easily accessible, that is why.
Geoff, I use ATS probes, although I have two 300 psi transducers, they are different versions, normally I set them up to be on the same level, this time I did not. Eventually I will have two of them that are the same revision and another three valve Ford hose.
Remember the vacuum gauge, great tool. Still is
Thanks for sharing Rusty. Great write up. Screen captures & pictures are awesome to have along w/the case study. Gotta admit I don’t own a pressure transducer but man that’s awesome! W/in the hour to diag and make the call. Thanks again for sharing.
As with any equipment, the more use it gets from you, the better and quicker the end result. Thanks for sharing your thoughts!
Nice job Rusty! I like the path you took and the diagnostic thought process! Even though you are supposed to trust your scan data...sometimes they do cheat on you...lol Happy New Year to you!