Okay guys I took off my SC a year and a half ago and put on a turbo. We have been trying to tune it for awhile now but kept running into problems. I finally took it to a dyno last weekend, turns out he found the same problem. Around 5800-6100 rpm he said it will misfire and cut fuel. He thought maby a ground issue or crankshaft sensor.When we got home we checked the wires going from the icm to the pcm and icm to the crankshaft sensor and camshaft sensor. Everything seemed to ohm out fine. Replaced the crankshaft sensor and put on more grounds. No change. The only thing I changed was moving the icm and coil packs off the engine besides the turbo stuff obviously.It never did this SC. It pulled all the way to 7000 SC. Anyone have any ideas. It doesn't set a misfire code. Not sure what to do with it now.

Did you do a crank case relearn? If you ever remove the balancer pulley and/or the crank sensor this is a requirement. It made a big difference in my 3800SC that I was having problems tuning. This sensor detects misfire and if it isn't 100% in sync it will throw faulty readings to the PCM.

another possibility is the ICM could be failing.

Starting to sound like I'm maxing out my maf senser. I'm using a Lq4 maf before the tb after the turbo. Sounds like I have to put a mini afc on it. Seems so weird at 7# of boost to maxing out the maf. A friend of mine is pushing 14# with a stock maf on his GP with no problems. Guess I should have left the stock one in.

did you update the MAF table in the tune for the LQ4 MAF?

Yep. We put the ones in it that are on the zzp website. And when the tuner at the dyno shop tuned it, he also adjusted it. Thats what doesn't make sense. I see a lot of people using this maf and I don't see anybody talking about their mini afc.

Could it be spark blowout? What are your plugs gapped at?

quote Originally posted by babyboy761: Could it be spark blowout? What are your plugs gapped at?

very good possibility, what are you running for an IC?

You don't need a mini-afc to rescale the MAF. You can mod the MAF itself to rescale it by soldering on a resistor across the shortest bar and the middle long bar inside of it as shown the following picture. You can start with a 1.4k ohm, 1/2 watt value resistor and see how that works.



You will need to rework your entire MAF calibration table in the PCM tune if you do the resistor mod to the MAF, so keep that in mind.

Concerning spark blow-out, I was using Denso Iridium plugs and could only run about 13psi of boost with a 0.055" gap before experiencing spark blow-out. Dropped the gap to 0.040" and ran it up to 18 psi recently without having any problems. Other brands / cheaper grade plugs may produce different results vs. what gap you run them at.

-ryan
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[This message has been edited by Darth Fiero (edited 06-11-2014).]