Help Need: Misfire Issue

Hello everyone. I have a BK 3 MPS. Has misfire

Issue started after a mechanic degreased the engine bay looking for a transmission leak. My Cobb ap v3 gave me P0304 engine misfire cyl 4 code, i cleared that, then it threw P0303 misfire cyl 3, Then cleared that and came up with P0300 random misfire. We checked Plugs, Coils, Intake for leaks, Boost leaks, Came up with nothting. After a week or so, got into the car and the problem was gone. (figuring something dried out?), Anyway, heavy rain the other night and after that the problem has returned. Taken it to be looked at and they said it may be the Fuel injection Air flow Meter (which has been thoroughly cleaned), I'm just wondering how it could be that if the issue came then went away? Otherwise could water be getting into the air flow meters wires maybe?

So when you unplug the air flow meter the car doesn't misfire, but since it puts the car into limp mode with set A/f ratio does that mean it could still be something else, like TPS related?

If the Throttle position sensor or wiring was damaged or shorting, could that still cause misfires at idle?

Any Advice would be very appreciated thanks

Mods? Do you have an SRI? Could be filter getting wet and gunking up the MAF, or a clamp cutting the ECU wires which are shorting when they get wet?

Misfires... Possibly spark plugs? Gapped properly?

Plugs are gapped correctly, isn't plugs. Yes has got SRI, (hpfp, bigger tmic, bnr s3). just swapped another air flow meter into it today, didnt help the issue sadly.

Quote:

---

Originally Posted by Joe

Plugs are gapped correctly, isn't plugs. Yes has got SRI, (hpfp, bigger tmic, bnr s3). just swapped another air flow meter into it today, didnt help the issue sadly.

---

What plugs?

Tune? Logs?

Random misfire codes have appeared for me before, in my case it was a maf cal issue but massive air leaks post maf outside of fuel trim threashholds is my guess! As the intake is right in the way for viewing the trans from above I suggest looking there and the good old wiring damage due to hose clamp orientation.

Follow up!

Over the Xmas break I was lucky enough to have this car delivered to me on a tow truck in an obvious sick state of health and was able to begin full diagnostic attack of this issue.

The car had some prior history of very poor repair methods which included an engine change as well as just general shit workmanship, in short they contributed to the fault.

Visual inspection initially picked up on boost/vac leaks from incorrectly fitted hoses,clamps,pcv and stripped bolts almost holding on bpv as well as the wiring being incorrectly routed and all 3 earth tails but floating in the breeze!

A DTC check after clearing all history revealed cylinder x misfire which gave me a starting point for trouble shooting. In addition to checking the dtc with ap I was able to monitor pcm inputs and noticed that the fuel trims and afr where showing up as perfect which it was clearly running super rich!

I proceeded to fix everything I could see was wrong and returned the car back to how it should be ( this step makes it hard to positively find the cause of the fault but catch 22) Much to my surprise absolutely nothing improved and I still had a sick car on my hands.

From this point I followed the trouble shooting fault tree for cylinder X misfires ( read to shop manual if your interested)
during the fault finding process many of the tests were inconclusive and any doubtful results were inconsistent when compaired to known good vehicles.

I was confident that I had correctly diagnosed a faulty pcm but I wasn't going to buy a $2000 PCM without being 100% sure! Lucky for me I have a good support network and Troy was kind enough to send me a full cars worth of modules! Unfortunately this option didn't work as planned and I needed an alternative to confirm my diagnosis. Thankfully I have built a good relationship with some fairies who were able to program the borrowed system and ultimately confirm my diagnosis of a fried pcm!

The instant the car started it ran like garbage due to the large un calibrated maf however I now was able to monitor stft's outside of thresholds, I also tricked the maf and was able to free rev the car misfire free.

An unfortunate situation for joe as he hasn't been able to enjoy this car, so hopefully with the time spent and all underlying faults repaired he may enjoy his ride into the future!

Make sure that repairs are completed correctly or you will have a ticking time bomb.

Great work Mitch! Know you did everything in your power to get that car working properly!
Fingers crossed things work out for Joe, and he finds a pcm for reasonably cheap!

What makes a pcm fry itself? I'm very good with board level pcb repairs. If it's just fried components it's possible I can rebuild one.. Never have before but as I said I'm very confident in board level repairs, bga, smd I have some expensive equipment for doing so. Sourcing the ic's it may need could be a problem.
Anyway just an idea I thought I'd mention.

Bad earths are common when muppets attack things outside of their capabilities.