I have had the same issue with my 94 for a year and have read every "rough idle" post hoping the silver bullet fix had been found. The SC has 100,000 miles on it now with a fresh long block at 65,000 miles. I bought it with 73,000 miles. I replaced every module and sensor and as many of you know it ain't cheap. Obviously, I'm still missing something. I have solid mounts and removed all of the vacuum hoses to eliminate vacuum leaks with no luck. I have teflon IC gasksts and sprayed carb cleaner to ensure no leaks. I replaced the fuel injectors (only takes me 2 hours to do the whole job now) and matched MAF tubes. I contacted C&L and they agreed my setup was right. I have an ACTRON code scanner and ran the cylinder balance test yesterday. Cylinders 4 & 5 failed. I ran the test again and cylinder 4 failed. I ran one more time and it passed. Shut the car off and let sit for 20 mintues and ran the test again. Cylinders 4 & 5 failed. I'm not sure what it does doing this test. I don't know if the fuel is shut off or the spark is interupted. Anyway, I swaped coils between my 90 XR7 and the 94. No joy. I pulled the battery cables off to reset the computer and let it learn the changes with no luck. I just installed new wires and iridium plugs. No joy. I even bought an MSD DIS-4 ignition box and the 2 required adapters hoping that would make a difference. It did not. Mine now has the added feature that when I accelerate from a stop it is very slow to respond especially with the AC on and then takes off. I have to almost mash the gas pedal to get it to go. It appears to run good on the road at 50 to 70 MPH but I get terrible gas mileage. Around 10-12 MPG. The real frustrating thing is I never get a hard CEL to tell me what is wrong. I do get a momentary CEL sometimes when I'm climbing a hill in OD but as soon as I get on level raod, the CEL goes out. The code does not latch so I'm back to square 1 with diagnostics. So as you can see I'm really enjoying my SC. Right! I would be one happy camper if the 94 ran as strong as the XR7. And that is the other frustrating thing. I did the same mods on my XR7 as the 94 and the XR7 runs really strong. The only 2 primary differences between the two setups is different trannys and different ignitions.
Still searching for the silver bullet fix!
Ed Springer
90 Black XR7 5-speed: 70mm TB, Fresh Air Intake, '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, UD Pulleys, 190 l/h Fuel Pump, 36 lbs Injectors, Headers, Magnaflow Muffler (no cats) with stock resonators, 3:27 Gears, Ripper Shifter, 73mm CL MAF (Blue Tube), Magnacore Wires, NGK Iridium Plugs, Royal Purple Lubricants and Rear Spring Air Bags.
94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, 190 l/h Fuel Pump, Headers, Raven Muffler (no cats) with stock resonators, 3:73 Gears, Accel 36# injectors, 76mm CL MAF (Gold Tube), Magnacore Wires, NGK Iridium Plugs, Royal Purple Lubricants, TRANSGO Shift Kit, Pro-Torque 2500 Stall TC, Haydon Auxiliary Transmission Cooler, Tokico Struts & Shocks, American Racing 17” Sniper Wheels, Michelin Pilot Sport A/S Tires and 235 RWHP with 315 LB-FT Torque.