I have been chasing a problem for a month now....Need some help.

My new 383 with a d1sc has been carboning plugs after approx 125 miles a set. They are ngk tr6 plugs gapped at 35. Ignition is a five year old msd6btm, new msd blaster coil, accel 300+ wires, dynatech opti which was recently serviced and no problems found. With new plugs it runs great till they start to foul. At this point does not seem to be an ignition problem. Data logs show Lts at 128 and Sts at 135ish. I am going to change plugs to autolite 103s and change the gap to 38-40. I have also made an adjustment to the throttle body(58mm) and the tps switch set at .067 I made the adjustment due to the car not idling smooth when coming to a stop. It was kinda falling on it's face and trying to rebound.

Does anyone have any ideas on the fouling issues?

Does anyone know if the tps adjusted closed too much and/or tps switch out of adjustment could cause this motor to foul plugs in 125 mile time?

Any help would be greatly appreciated

 

How does your blower setup add the extra fuel for boost? An FMU, or tuning of the stock PCM? What kind of fuel pressure are you running? What size injectors?

You really need to provide full data on the engine... "383 with a D1SC" it totally inadequate for this kind of analysis. What cam? Who did the tuning? Injectors? Exhaust system? etc. etc.

Your data logs sound odd.... short terms should average 128 in closed loop, swinging above and below 128 over a range of maybe 120-135. If the short terms are always at 135, the long terms should increase above 128, until the short term average drops to 128. That's the basics of the PCM's "learning" ability. But then without knowing who tuned it and what kind of tune they used, its hard to tell. Any chance the tuner "locked" the BLM's?

Have you tried posting this question in the Forced Induction forum, for input by other SC users?

 

You shouldn't adjust your TPS because it's "...not idling smooth when coming to a stop. Kinda falling on it's face and trying to rebound". I bet you need to make some throttle stop screw adjustments to get your IAC's back in the 30-40 range.