Fingers

K, the other thread is confusing, so i'll start a new one.

The inconsistent idle quirk went away after I re-re-readjusted the tps and set the idle speed with the jumper. What have i done already? Used throttle body spray to clean the tb, ran marvel mystery oil through the gas and oil... checked for vacuum leaks using propane... checked TID for cracks. Found none.

That being said, the only problems now are:
A) when revving engine from under the hood, between 1000-2000 RPM, there is a random misfire.
B) On a hot day, when the engine is hot, shut down... and say i go inside the store for 10 minutes... come back try to restart it... it will misfire, stumble, and all that good stuff. Sounds like a 4 cylinder engine running on 2 cylinders. If i can keep the revs up, it runs fine. Or if i go for a quick drive (5-10 seconds), the idle is back to normal. Mind you, it hasn't done it since i re-adjusted the tps for the last time, and set the bac properly, but i'm sure it will if the conditions are right.
C) If the car is not COMPLETELY warmed up... like 80% through its warm-up cycle, it will stumble and hesitate randomly, it seems. Boost/no boost/rpm seems irrelevant.
D) There is a boost spike@10 psi... it then settles down to 8-9PSI, but i dont think it should be that high to begin with, considering i have a stock motor, with no mods aside from Autometer boost gauge. Stock boost gauge is VERY inaccurate, which is why i think the boost sensor might be fubared.

My suspicions are:
1) Air filter, it is dirty, but i want to wait to be able to afford the intake i want before i replace it twice.
2) The issue is temperature dependant (all except d)... so I'm thinking its the MAF - all the signs are there. Definitely not the tps. Checked MANY MANY MANY times
3) Fuel filter perhaps?
4) Leaking/dirty injectors?

The car is pulling no codes... when accelerating, it pulls quite strongly... so the motor seems to be in very good shape (20,000km on it... mazda crate motor). Intake manifold gasket was recently changed by mazda.

Now my fingers hurt. Your turn
Thanks
-Ross

Fingers

Oh yes, grounds... i've thrown on a 4ga ground from the battery to the coil, and from the coil to the engine block.

My other suspicion is the ECU ground. Does this sound like something the ecu ground would do?

Icemark

I had a simular problem with a S4 Turbo (except the random misfire was between idle and 2000 RPM) that had a blown BAC control transister in the ECU. You might try swapping ECUs.

Black13B

iTrader: (1)

i wonder how much a j/y will charge for an ECU..

are they ECUs different between the tIIs and the N/As? (ill assume yes)

fingers theres a black S5 TII at the scrapyard in my area with a pulled drivetrain.. i took a few parts off it and checked it out.. i believe the ECU is still in it..

i can see what the want for it and tear it out for you or something..

Fingers

Sweet. Check if the ECU is in, as well as the AFM and the TPS. I'd be interested in swapping all three and seeing if the problem persists. As well as the BAC! PLEASE!!!

Icemark

Yeah, the N/A use different ECUs than the Turbos.

I know its been posted before, for what goes with what, but off the top of my head, the N32x (S4) and N35x (S5) ECUs are for N/As while the N33x (S4) and N37x (S5) are for the Turbos.

The only exception is the N338 which will run either a 88 turbo or 88'vert (but not the 88 N/A).

Fingers

Bump!