1 Attachment(s)
Fouled plugs and misfiring -- EDIT
Hi All,
I have a dilemma related to the state of my '97 VR4 engine that "seems" to defy logic. The engine has 150K miles with no issues other than jumped timing once.
I've recently did performance upgrades that may very well surfaced a problem I've had for a long time of which I wasn't fully aware. By attempting high teens boost the issue became apparent. The car is at a local shop with a 4wheel dyno that specializes in WRX's, STI's and the like. They are well known in the area and always have a full lot of cars up for builds or tuning.
First, the symptom:
The engine is fouling all the plugs with just a few miles of driving. Pulling them out they look like they were spray painted black. At atmosphere while the plugs will foul the engine runs fine but will misfire at high revs under load. The engine idles fine with no hint of roughness, no valvetrain noise. Boost is out of the question as the misfire becomes a big issue.
The parts upgrade & maintenance parts:
Injector Dynamics ID1050X Injectors 11mm (Blue)
Adaptor Tops Denso Lower Cushions (Set of 6)
BKR7E NGK Spark Plug
AEM 91-97 3000GT / 92-97 Stealth R/T Turbo Series 2 EMS
Delete MAF
Mitsubishi 3000gt coil packs
Plug wires
Install EBCS - HKS boost controller is routed to turbos.
Turbosmart BOV Plumb Back Uni 38mm-Black
Gates Racing timing belt
Inspected and cleaned throttle body and IAC
Smoke tested - leaks eliminated
Examined for possible cause of the symptom:
Replaced plugs multiple times
Eliminated EGR
Compression test - OK
Leak down on front cylinders - OK (within 5% of each other)
Multiple maps tried including back to stock AEM map
Replaced coil packs
Checked fuel pressure - OK
Checked F:A ratio with 3 different gauges - all agree
They see nothing usual on the AEM side. All parameters align with what should be a proper tune.
I would really like one of the experts here to give some guidance about what to check/look at. If they have experienced this exact problem. Any suggestion is very welcomed!
Thanks in advance ............ Dennis
EDIT: Sorry for the delay getting this for you guys. Spending most time on my '70 Firebird RestoMod project. Attached is the AEM-EMS data file some of you requested. The only way I could attach it was to change the extension to'PDF'. After downloading, please change the extension back to 'CAL'. Hope this helps.
EDIT #2: here are additional comments
Yes both temp sensors are working and reading correctly on the aem. i thought we already tried a different ecu as well but i will check my notes and or try another just to rule out.
Yes every cylinder [is involved]. It doesnt want to tip in. Just hesitated then revs up. Unless we put a lot of fuel in it, but then it will just foul plugs.
Hopefully, ths gives you more info to chew on.
Addendum to Original Post
In the original post I forgot to list upgrades I did ~10 years ago. After those upgrades and a great tune by Ray the car performed completely differently. Came off the dyno at 410AWHP with same torque (~408). Not a monster by any means, but respectable for an old fart like me. Upgrades ~10yrs ago:
3Sxecutioner gen 1 turbos
550 injectors
Larger SMIC
Dejon hard piping
Supra pump (not hot wired)
Tanabe Medalion cat back
3SX downpipe with high flow cat
The reason for the upgrades this time was I had begun to get stumbling when in boost under load. Thought that its been 10 years since the last tune, even though I put on only ~15K miles on it, so it was past time to look into everything. And if there was any significant tech improvements I would make those changes. Hence, the new injectors and the AEM II.
That's it for all the engine upgrades past and present. I realize not all I listed may have contributed to this problem. Listed only for the sake of completeness.
Dennis
