2.5L misfire at part throttle/idle (Page 1/1) Brapmaster22 JUN 01, 11:27 AM Hey all, I've got a 1984 Fiero 2m4 4-speed that's developed a misfire at part throttle and sometimes idle. If I fire it up and don't touch the throttle it idles, but if I rev it up at all it'll stumble and die. Then it won't fire back up without giving it some gas. When I'm cruising on the road at part throttle it's missing, but if I mash the gas it goes away. Very frustrating! Idle air control valve was replaced a couple months ago No vacuum leaks, I checked by spraying around the intake/throttle body Plugs and wires replaced a couple months ago, just took them out to inspect and gapped them to .060. I moved the wires around to ensure they weren't grounding out. No check engine light. Timing set at 8 degrees Not sure where to go from here. Any help would be greatly appreciated! 1985 Fiero GT JUN 01, 03:42 PM quote Originally posted by Brapmaster22: Hey all, I've got a 1984 Fiero 2m4 4-speed that's developed a misfire at part throttle and sometimes idle. If I fire it up and don't touch the throttle it idles, but if I rev it up at all it'll stumble and die. Then it won't fire back up without giving it some gas. When I'm cruising on the road at part throttle it's missing, but if I mash the gas it goes away. Very frustrating! Idle air control valve was replaced a couple months ago No vacuum leaks, I checked by spraying around the intake/throttle body Plugs and wires replaced a couple months ago, just took them out to inspect and gapped them to .060. I moved the wires around to ensure they weren't grounding out. No check engine light. Timing set at 8 degrees Not sure where to go from here. Any help would be greatly appreciated! Use a multimeter to check for dead spots in the TPS, it should have a smooth range with no jumps in voltage or dead spots that might be telling the ECM the wrong position at part throttle. Brapmaster22 JUN 01, 04:14 PM quote Originally posted by 1985 Fiero GT: Use a multimeter to check for dead spots in the TPS, it should have a smooth range with no jumps in voltage or dead spots that might be telling the ECM the wrong position at part throttle. Closed throttle reads .5v and smoothly climbs to 4.5v. Those numbers are in the acceptable range, right? Brapmaster22 JUN 01, 05:50 PM The rough idle issue seems to be going away, it's just that it misses when it's at partial throttle and after you release the throttle it fumbles around for 5 seconds then goes back to idling on 4 cylinders.