Lean Misfires at 2700-2800 rpm

[F27Corsair]

Badass- im not sure which wire it was, i just re-checked all of the connections. Any of the wires being off could cause a huge problem though. If i were to guess, i think either the power or ground wire were to blame.

[DoctorDex]

Originally Posted by magn1t

You've probably got an ignition fault.

That causes the tach to jump and for the AFR to spike.

I'm interested in this idea. Does anybody know what else can go wrong in the stock ignition system that could cause the symptoms we've been having?

I replaced my coils, wires & plugs with the hope of fixing the problem - no go.

That leaves PTU and ECU, but both of these problems usually present differently.

Declan

[J-Ville VR-4]

Originally Posted by magn1t

You've probably got an ignition fault.

That causes the tach to jump and for the AFR to spike.

Steve

I dont see how that can repeatedly happen at 2700-2800rpms though

[venik]

Originally Posted by DoctorDex

I'm interested in this idea. Does anybody know what else can go wrong in the stock ignition system that could cause the symptoms we've been having?

I replaced my coils, wires & plugs with the hope of fixing the problem - no go.

That leaves PTU and ECU, but both of these problems usually present differently.

Declan

try lowering your gap, 40 thousanths is extremely high, i was getting spark blowout at .036 with almost no load, with dr650s i'd say 28-30 thousanths

[venik]

and to explain the difference in AFR between front and rear banks, the plug thats gapped widest could be on the front bank you misfire then ecu pulls fuel and next crank is on the rear bank making it run lean, then it goes back to the front bank and its flooded with fuel making it run rich

[John Monnin]

If his car is like mine it doesn't lean mis-fire at higher RPM or at higher boost, so that eliminates the posibility of the ignition system not being able to jump the plug gap.

[badass3000]

well, my ECU is steadaly getting worst. Now im running on a max of 5 cylinders, I get false CEL that cant be read by scantools, and my Tach sometimes reads 1600rpms lower. Car is running like shit.

[venik]

Originally Posted by John Monnin

If his car is like mine it doesn't lean mis-fire at higher RPM or at higher boost, so that eliminates the posibility of the ignition system not being able to jump the plug gap.

i said in my post i was getting misfire with almost no load, a gap of .040 should only be used on N/A, i lowered my gap to .030 and its gone, even though you're barely putting load on the engine, it still has more pressure in the chamber than at idle. I'm not saying all of you have a gap too wide, but problems like hesitation could have alot of sources, wires, plugs, coils, or the ecu. its obvious that doctordex's plug is 10 thousanths too high, actually he might even need a gap thats lower than .026, depends on how much boost hes running at cruise and WOT, i know people who boost 20+ psi use .022 or lower

even though your not going into boost there is MORE compression at cruise than at idle, just look at your boost gauge, if you still dont believe me, check your boost gauge from 2200-3000 i bet as soon as your in the right rpm range theres a maximum compression your car will let you have before it missfires/blowsout. im not going to argue with you, theres nothing for me to gain, so if you dont believe me GL on fixing your car, because i dont know if you ever will, unless its your ecu which is a possibility.