KA-T stutters under load

[UncleBen]

Disclaimer; this will be a long post.

So to begin, a few months ago I was out one evening doing a little spirited driving as I hardly ever do, and for good reasons such as this. A plug wire fell off the distributor cap somehow, causing a miss, of course. I stop and attach the wire back to the dist. cap, start the car, still running very rough. I go back to ensure all the wires are on securely, they are, but the car continues to run very rough. I limp it home and almost get run over in the process, pop the hood, and the plug wire had fallen off again. Great. I let the car sit overnight, I reattach the plug wires, start the car and all is good. I get on the road and attempt to do a pull; car boosts up fine, gathering RPM fine, until about 10psi boost/3200PRM it starts sputtering and cutting out, almost like a fuel cut or rev limiter. I am off the throttle at this point, cursing. I move to a higher gear, do another pull. Boosts up fine to 10psi, gets to about 3300RPM and begins to cut-out again. I stay in the throttle and it continues to spit and sputter, but keeps gaining more RPM's until maybe 4500RPM, when it just stops and backfires very loudly. Car runs perfect under a regular load, boosts just fine as long as it's not high boost and a heavy throttle load.

I put new plugs, new wires, new distributor cap on the car. Runs much better! Problem still persists. I switched MAFS (N62) and the problem persisted for a couple days, then it just went away and was perfect! The guy's MAF that I took needed it back so I put my original one back on, expecting the problem to come back, but it didn't! Still ran great! Took the car to the track a couple times, been running super strong. Well I find someone that wanted to buy the car and guess what, problem magically returns. First thing I do is switch MAFS again but never did fix the problem. I finally switched distributors all together, problem still persists.

This is a stock block KA, stock ECU, SAFCII tuned, Deastchwerks 555cc injectors, N62 MAFS.

Anyone have thoughts? I have not checked compression yet and am replacing the throttle position sensor this weekend, as the SAFC indicates the throttle sensor voltage going crazy when the car begins to sputter. Now this isn't because I'm moving the gas pedal all over the place making the voltages change, it isn't that violent of a sputter.

Ideas?

[C-Kwik]

Spark plug gap?

[UncleBen]

They are properly gapped at .028" as they always have been.

[240sxvaj]

Do you have a wideband?. i had a problem similar and found out that my injectors crapped out on me. As i put load on the car, it would stutter and feel like boost leak. put in my new injectors and problem solved. check your afr.

SAFC's are crap by the way. before i got my ecu i was running afcneo w/450cc and it seemed like sometime it doesnt want to work and my car would just run rich for like 20min and then works again.

[frsh13]

Sounds very similar to whats going on with my car right now. We should make a complete KA-T section list of EVERYTHING to possibly check if your car is sputtering. I feel like every other week we have a post like this.

[UncleBen]

Thanks for the replies.

Guy on ka-t.org said he had a similiar issue and it ended up being a bad connection on the injector where the harness plugs into them. I will clean the connections with electrical cleaner for a quick test and see what happens.

I tuned the car with a wideband but then had to return it; I have it available to use when I need it though. I will install it this weekend and watch my AFR's when the car spits around. This was one of the plans for this weekend anyway, so you guys reassuring me helps.

I just drove the car for the first time today since like Tuesday; just a simple drive to work made me fall back in love

[UncleBen]

and 240sxvaj, you hit it dead on; feels like a boost leak! Stupid injectors, I had problems with these things when I first turbocharged the car.