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Hi guys
Looking for any advice with diagnosing misfire on a 2004 5.7 Dodge Ram, in UK and not familiar with this at all.
Not gone into detail yet as didn't have much time but only has P0300 code, doesn't appear to have captured freeze frame for some reason. Horrible -18 and -33 ltft, stft at idle is +2 and +3. Has nasty misfire feel at idle and stalls after being revved.
Guy has replaced crank and cam sensors, plugs, 4 x O2 sensors and coil packs (strange HT lead / coil pack setup!), mostly Mopar parts which doesn't mean a lot to me.
Quick vacuum test showed 18hg at idle, appeared to behave normally without signs of blocked exhaust.
MAP 1.5v at idle.
Was thinking of doing fuel pressure test and look at EGR valve, hoping there's a chance someone here will be experienced with these and give some direction or maybe point out something common.
For reference I'm using MS908P as my Verus Pro does not cover US vehicles. Can obviously go OBD with either.
Thanks in advance
Ezi
I'd suggest a relative compression test before digging too deep. 5.7's are known for all kinds of mechanical failures. Plus, the fuel control system gets completely screwed up with a mechanical issue.
Your Autel should (hopefully) have the Which Cylinder is Misfiring function, for live misfire counters. They may call it something else? Keep your eyes open, as always.
Thanks very much, relative test is a good call.
Misfire counters and mode 6 were proving a bit elusive, was only meant to be a quick code read for the owner but ended up getting more involved with not much time to spare.
Next visit can be more detailed I hope.
Speaking to him this evening it seems this whole situation is intermittent which I hadn't realised, gets worse!
Ltft 's tell me a vac leak. Does the missfires happen when cold or hot or all the time. If it's when it's cold would say to smoke test or spray water around intake and listen for water being sucked into intake. Also check egr tubes and valve and various vac lines as well as intake air tube from filter housing to engine for torn/cracked intake tube if it has a maf by filter housing
LTFT's are negative. This indicates a RICH condition. The computer is subtracting fuel. Vacuum leaks, generally, create LEAN conditions, with positive fuel trims.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
Thanks for input guys, at least new parts should be ok even though it probably didn't need them.
Positive condition with vac leak would have been simpler but sadly not.
No MAF on this thing, just MAP.
Not at all what I'm used to, wish I was two feet taller to work on the thing!
All suggestions welcome before I find time to get back to it next week, thanks.
On a side not does anyone have any information on the coil packs with HT leads system, don't think it's anything to do with the problem but interested to see what it's all about?
Tried googling but most similar vehicles seem to have standard coil packs, not sure why there'd be HT leads thrown into the mix?
Thanks
Ezi
ezimoto wrote: On a side not does anyone have any information on the coil packs with HT leads system, don't think it's anything to do with the problem but interested to see what it's all about?
That engine is 2 plugs per cylinder. The ignition is COP/wasted spark for want of a better description. Each coil is COP and the HT lead goes to a plug on the cylinders TDC twin on the other bank.
