Misfire troubleshooting -- MAF

[Reaper]

Running down a idle misfire and while I replace the air filter, what cleaning of the associated intake should I do? I see the MAF is installed in the air cleaner lid and the coils are fully accessible from both sides without even removing it. Should I wash those down with MAF spray cleaner while the cover is off? What else should I clean while in the area and is there a specific technique? This is a rallycross car so I'm naturally suspicious of dirt-caused issues. Otherwise it's a low mileage stock engine except for Stratified street tune.

 

[TyphoonFiST]

Running down a idle misfire and while I replace the air filter, what cleaning of the associated intake should I do? I see the MAF is installed in the air cleaner lid and the coils are fully accessible from both sides without even removing it. Should I wash those down with MAF spray cleaner while the cover is off? What else should I clean while in the area and is there a specific technique? This is a rallycross car so I'm naturally suspicious of dirt-caused issues. Otherwise it's a low mileage stock engine except for Stratified street tune.

That is NOT a MAF even though it may look like it. Our cars run off of the map sensor/ Speed density. It's just used for monitoring Incoming Air Temps. Sometimes I wish our FiSTs were MAF vehicles though! You can clean it if you'd like....it won't hurt anything. So clean away with some MAF spray if you feel so inclined!

Sent from my SM-S908U1 using Tapatalk

 

[TyphoonFiST]

You may need a scantool that has a program called Mode 6* it will be able to identify which cylinder is misfiring even though it hasn't met the manufacturers/Fomoco threshold to set the MIL light/ Check engine light off

 

[Reaper]

Thanks for setting me straight on the MAF. My current scan tool showed three misfire codes. From memory, one was random events, one for cyl 2 and one for cyl 3. The engine codes come and go. Sometimes I've removed them with a battery cycle. Sometimes with my code reader. But it doesn't really matter. the car DRIVES fine with full rev range and apparently full power. But at a standstill in neutral or with clutch down, the engine will sometimes not rev past 3000rpm. Sounds like a launch mode. But drive off and the "limp mode" is gone.

I did a full rallycross with this issue and no impact. My only actual problem seems to be I can't get it onto the trailer. In addition to not revving past 3000, it can't go more than five feet up the trailer ramp before the engine dies, regardless of throttle and clutching. Kill the codes and it stays "normal" long enough to at least get it onto the trailer. Sometimes I can just shut off and restart the engine and it will do the trailer. Apparently driving onto a trailer is different than just driving on the street or track.

You know way more than I do about these things. Can you recommend a troubleshooting sequence? Plugs, coils and an air filter are going in this morning. Racing this weekend, with or without limp mode.

 

[Reaper]

Update. It seems the misfire codes and 3000rpm limit are likely two different things. Alex at Stratified says the 3000rpm limit is a built in launch control that I never use because you don't power launch on dirt -- no point to just spinning tires forever.

So then it seems I'm just dealing with typical Fiesta misfire issues which he says are common. Said to check into a common grounding issue that causes misfire. Anyone know more about that? He said there may be a Ford bulletin about it for early cars. Don't know if 2016 is considered early.