Odd Misfire

s13eater · #1 30-07-2012, 20:10

air flow meter maybe.

Nattman82 · #2 01-08-2012, 15:17

Quote:

air flow meter maybe.

Im thinking along the same lines. As its only under very specific conditions, ie throttle possition and engine speed. As I said under boost it pulls fine which to me rules out a spark issue as surely when the cars being driven hard any weakness in the ignition side would show up more? I dunno. Thankfully I have a mate who also has an S12 and im gonna pop over to his later to borrow his afm off his car and see if that makes a difference. Also trying to source an afm just incase. Will keep you posted.

Nattman82 · #3 01-08-2012, 19:30

Well, changed the air flow meter over for my mates which was working fine in his car but it made no difference.
On the way home I noticed a few more details to the issue, when the car is missing/hesitating there is black smoke pouring out the exhaust but when the boost comes in all smoke goes away and the car pulls as normal. Also, the problem is significantly reduced when the car has full warmed up and has been driven for a while. I took the plugs out today and apart form being a bit sooty they're fine.

So now theres a vast number of things to start guessing. Gonna start with the cheapest bits and go from there.

caz4244@essex · #4 01-08-2012, 20:33

black i think.is unburnt fuel from the misfire i believe maybe a compression test ?

s13eater · #5 01-08-2012, 21:38

try a different fuel reg too as they can go wrong and give you to much pressure.

Nattman82 · #6 02-08-2012, 20:42

Rite, wee update. Fine in the way to work thismornin but fuckin nitemare on the way home. Pulled the fault codes off the ecu and got code 22 which is fuel pump. So Im gonna investigate that area first, check wiring, relay etc before replacing the pump. The iregularity of the fault had me a bit perplexed, like I say it was spot on thismornin on the way to work but n the way home it would barely move. Symptoms consistent with my old xr3i just before the fuel pump threw in the towel so im pretty confident ive found the fault. Just need to be 100% before forking out £75 on a Walbro pump.

Related quiestion, are all the Walbro pumps the same? See some with specific fitting kits but closest to the S12 is an S13 DET kit. Would that do the job and are they hard to replace?

s13eater · #7 02-08-2012, 22:34

i usede a walbro for a pulsar, they are easy to fit.