Another Rough Idle Question - ANY IDEAS!

As you can see below I have modified my '94 SC quite a bit. This idle problem has been around since I got the car in Sept 02 and the mods have not made it worse or better. The car runs great on the road. When I go to STOP the car idles fine at about 750 to 800 RPM for about 2 seconds after I stop then drops to around 600 RPM and idles real rough. It does not cut out but it damn near shakes the radar detector off the windshield. I push it up into neutral and it idles like my 90 XR7SC. It holds right at 20 inches of vacuum in park. Acceleration from stop is great. I checked and cleaned the EGR valve when I recently replaced the injectors. My 90 XR7SC is a 5 speed and idles a little rough but nothing like my 94 SC.

Also, over the last 18 months I have replaced the IAC, ignition module, ignition coil, crank sensor, harmonic balancer, camshaft sensor, water and SC plenum air temp sensor, atmospheric pressure sensor, TPS, computer, fuel pressure regulator, fuel pump, motor mounts (solid), O2 sensors and KNOCK sensor.

Any ideas or suggestions would be appreciated.

Ed Springer

90 Black XR7 5-speed: 70mm TB, Fresh Air Intake, '94 Supercharger, 5% SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, 190 l/h Fuel Pump, 36# Injectors, Headers, Magnaflow Muffler (no cats) with stock resoantors, 3:27 Gears, Ripper Shifter, 73 CL MAF and Magnacore Wires, NGK Iridium Plugs.

94 Red SC Auto: 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, Raised SC Top, I/C Fan, Underdrive Pulleys, 190 l/h Fuel Pump, 38# Injectors, Headers, Raven Muffler (no cats) with stock resoantors, 3:73 Gears, 73 CL MAF, Magnacore Wires, NGK Iridium Plugs, TRANSGO Shift Kit, ProTorque 2500 Stall TC, Haydon Auxiliary Transmission Cooler, American Racing 17” Sniper Wheels, Michelin Pilot Sport A/S Tires.

with my cam installed, i had to play around with the IAC screw thats located in the TB. If it was set too low i had the same problem, it would stumble when i come to a stop. I played around with that and got it right now. Its basically like a mixture screw on a carb.

edspringer said:

Also, over the last 18 months I have replaced the IAC, ignition module, ignition coil, crank sensor, harmonic balancer, camshaft sensor, water and SC plenum air temp sensor, atmospheric pressure sensor, TPS, computer, fuel pressure regulator, fuel pump, motor mounts (solid), O2 sensors and KNOCK sensor.

Any ideas or suggestions would be appreciated.

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Did you check for a vacuum leak in your intake? The pros use propane can with a tube on the end to check for leaks. If the idle surges you have found a problem.

When you replaced your fuel pump did you replace the evaporative emission valve on top of the gas tank? If the car sat around for a while this could have gummed up… This is a slim possibility.

Another possibility is your MAF…