What's causing my misfire/rich condition
 

While having my car tuned this past weekend my Evo suddenly fell flat on it's face during a WOT run/log (22psi on 93 pump). It seemed very similar to that of an IC pipe popping off or a massive boost leak when it happened. We pulled over and inspected everything, it all seemed to be secure. We turned the car back on and it started to misfire severely at idle and was puffing black smoke out like crazy.

We then thought it might be something in the tune, so my base map was reflashed back into the ECU, but it made no difference. We then pulled the spark plugs and found that they were carbon fouled. We bought some replacement plugs, (BPR7ES) gapped at .026, that temporarily seemed to fix the problem...For about two minutes. The car is back at the dealership (I JUST got it back from them last Thursday) and the tech so far said he is not sure what the problem is but that the ECU is dumping a ton of fuel at idle and causing an extreme rich condition.

I've been doing some searching on this problem and here is everything we have tested so far which has been unsuccessful:

1. Injen MAS was swapped for another (same part number)
2. Stock MAS swapped for the Injen unit
2. Spark plugs re-gapped to .022
3. Timing belt checked to see if it jumped a few teeth
4. Electrical connections to FPR, injectors, etc. checked for secureness

The technician did a compression test, checked fuel pressure, checked to make sure there wasn't oil in the sparkplug holes, etc. Everything checked out perfect.

Any ideas? The symptoms seem very similar to the timing being off. It idles very rough, puffs black smoke, and will occasionally stall out if you blip the throttle. The car does not seem to have any issues when you rev it up however- It' only at idle or low RPM.

Do you have a log of it?

What about the MAP sensor on the car what does it say?

i would do a boost leak test to make sure there isnt a leak.

Sorry, I mistyped. We did not log that last run, we simply wanted to verify peak boost since I had adjusted the MBC. I'm sure I can get the tuner to post up the previous logged run however.

I'm not very mechanically inclined myself so forgive me, but what do you mean by what the MAP sensor says? I know the technician said the MAP sensor was working fine. He was using what I'm assuming is some Mitsu data-logging equipment, I could see various readings from different sensors on his computer as the car idled.

Also, there the car is not throwing any codes if that helps.

The MAP sensor is a pressure sensor on the intake manifold its job is to tell the computer when the car is coming into boost. If it malfunctioned and said the car was in boost constantly then of course it would be dumping in fuel like crazy.

Second thing that does this is the MAF sensor on the intake tube before the turbo. If this malfunctioned it would be running really rough.

The last thing , i can think of, that could cause this ,however unlikely, is the Fuel pressure regulator on the fuel rail. Say it got stuck and the fuel pressure ended up being double what it should then it would be putting in way too much fuel.

i dont guys sounds like fuel cut to me!! in stock map.

I'd agree but he's saying its happening at idle :cool: fuel cut shouldn't be possible here.

Thanks for the explanation, that helps out. So if the MAP sensor was reading false information would it be apparent on my boost gauge (defi)? The strange thing about this whole issue is absolutely no codes have been thrown.

I don't believe it is the MAF sensor, Hellcat has the same Injen intake w/open element filter and MAF (part number was the same) and we swapped them for about 5 minutes with no change in the idle.

The FPR sounds like a good candidate to check; I'll call up to the dealer and see if the technician has checked that as of yet. Hellcat said he would post up a log of my car @ idle when the problem first came about.

What is an Injen MAF?

Do they actually make a MAF for the Evo?

Ugh sorry, typo again. I meant to say Injen intake and MAF, it is the stock unit.

The MAP is not used like this and has nothing to do with fueling in the traditional sense. The factory MAP sensor is 1 bar (only reads to zero vacuum)

The MAP sensor sends an atmospheric pressure reading to the ECU during start up to dial in the tune to current conditions / elevation.

The MAP sensor is also used to monitor emission functions.

what are the mods on the car?

Here is the complete mod-list:

-AMS 2.3 stroker
-IX turbo
-ported manifold
-ported o2 housing
-crower 272/272 cams
-Injen intake and ic piping
-(E-bay) intercooler
-Walbro 255 fuel pump
-Hallman Pro MBC
-Defi boost gauge
-AEM UEGO wide-band
-Act Xtreme clutch kit w/ streetlite flywheel
-stainless steel clutchline
-greddy RS BOV

The stroker shortblock was just broken in so I was trying to get it re-tuned this past weekend.

stock injectors?

Yes sir, still on stock injectors.