sbstar

Been fighting this stutter/misfire issue for a while now. Finally got around to getting the computer logging so I could try to get some answers. During cruising, seemingly at any rpm/speed, the car will randomly jerk/cut out/stutter/misfire whatever you want to call it. I am not logging my wideband but it goes full lean when this occurs. Sometimes it is a quick blip, other times it lingers for a second and then the car will go back to normal. It has never happened during WOT although at times wot doesn't feel smooth.

List of what I've tried:
New plugs
New Coils
Different ECU
Omni Map Sensor installed
Injector Resistor pack
cleaning the injectors
new fuel filter
new fuel pump
new fuel pump housing
new MAF
Cam angle sensor
Crank position sensor
Swapped to Evo 9 BOV
Stock intake pipe and an extremepsi intake pipe (both w/K&N)
Switch to Speed Density (see log from first cruise still stuttering)

Background on the car, took it as a blown engine/jumped timing. Rebuilt the head, replaced the block, and put everything together. It ran 50-100 miles from there until this started. It has had several times where I'll replace a part and it'll go 50-100 miles before stuttering again. Other times, it's undriveable as I can't even go a block without it stuttering over and over.

It has thrown a PO120 code a few times (TPS) but it checks out with a multimeter.
What I see in the log is O2feedbacktrim will often 0 proceeding the injectorduty from going to 0 as well. As best I can tell these are those hiccup/stuttering points while driving. The front O2 will 0 out when the injectordutycycle and injectorpulsewidth 0 out. Maybe a dying front O2? I'm really at a loss and starting to wonder if there is a short in a wire somewhere, truly starting to think about cutting my losses.

Project_Broke

iTrader: (2)

Have you tried disabling closed loop?

sbstar

No, I have not yet. I'll do that and report back though. I swapped in a new O2 sensor which did nothing as well. I'll give this a shot and then I'm going to start tracing wires as maybe it's a short somewhere?

Teal2nnr

iTrader: (7)

Keep us posted. When I had a similar issue with was my Exhaust cam position sensor. However, I see you've replaced that already.

LTEDDER

iTrader: (1)

Are all 4 Cylinders cutting out? or is it a miss on 1 cylinder?

I recently had a similar issue, after about 15-20 minutes of cruising, the car would start cutting out really bad (all 4 cylinders). This would not go away until the car cooled off.

The culprit ended up being an OMNI 4 Bar sensor

sbstar

All 4 cylinders cut out. It was doing it on the stock map sensor which is why I I stuck the omni 4 bar in there. Could be the stock one AND the omni were bad but its doubtful. Going to put new plugs in again today, add a couple grounds as I've seen these cars are picky, and try the closed loop thing. If none of that works I'm tracing wires which will suck but I seriously want to drive this thing to the shootout.

sbstar

Well, I'm lot 100% sure as I had checked it a few months ago. But, the TPS was way out of adjustment. Drove almost 100 miles without it happening now. I'll update if it comes back, but for now I'm hoping that was it.

sbstar

As a follow-up / conclusion to this for anyone searching in the future. Adjusting the TPS seemed to make the problem go away, but it returned, albeit with much less severity, after about 200 miles of driving. I made it to the shootout this year with light hiccups along the way. Figuring it still had something to do with the TPS I swapped them with a buddy who was planning on trailering his car home anyway. Pulling off my TPS we found it was a ISUMO branded TPS which appears to be a 13-14 dollar amazon/ebay special. Obviously, the oem unit runs you about 200 brand new and I would venture to assume this cheapo has pretty poor resolution. His oem tps has made the car run flawlessly and it even pulls harder without a doubt at WOT.

Teal2nnr

iTrader: (7)

excellent! glad to hear!