Furiyous
Probationary Member
- 21
- 22
- Mar 1, 2026
-
Tampa,
Florida
So, I have been trying to figure out the issue with my car for the last couple months (1997 GS-T Spyder). For some reason, after i start the car anywhere between 5-20 minutes (its random) it starts to skip/stutter like it has a slight misfire of some sort. The longer its running, the more it will start to misfire and skip. It has never stalled because of it though.
When initially start the car from a cold start, it runs PERFECTLY, no skip, no issues. After usually about 10 mins or so of driving/idling and the car warming up, it starts doing this, at idle, acceleration, doesn't matter. Its almost like a random irregular heart beat at idle in a split second.
Things I have done so far:
- 4 new Spark Plugs, NGK, with proper gap (0.28-0.31)
- 4 new Denso Spark plug wires
- New ICM/PTU, original Mitsubishi part
- 2 new Delphi coils installed as well
- New upstream Denso O2 sensor (was insane to get this thing out of the manifold from how stuck it was)
I will say it has been much better with those things replaced but its still there, especially on acceleration. Even very light acceleration it will skip badly. I do not know what else to check for. My OBD tool won't recognize the car for some reason (i think the car is too old for my ThinkDiag scan tool) so I cannot tell which cylinder is misfiring. I did check the cigarette lighter fuse, and its good (this controls OBD II power/communication I guess from what I have read).
From what I have researched, could possibly be injectors, injector resistor pack, ECT Sensor, Cam/Crank Position Sensors, vacuum leak or worst case the ECU. Engine Temperature gauge goes up to normal operation and stays there right below the halfway point so I am not sure its the ECT Sensor.
There is NO CEL that comes on at all, even when it skips, so I have no clue where else to look. I even unplugged the upstream O2 sensor to keep the car in open loop and still occurs. Any ideas would be helpful. My dad is going to try to bring his scan tool from work to check and see if it will communicate with the car so I can get a reading on the misfires hopefully some time this week.
Anything I miss? Should I check anything else while I wait for a scan tool?
Thanks for any input.
When initially start the car from a cold start, it runs PERFECTLY, no skip, no issues. After usually about 10 mins or so of driving/idling and the car warming up, it starts doing this, at idle, acceleration, doesn't matter. Its almost like a random irregular heart beat at idle in a split second.
Things I have done so far:
- 4 new Spark Plugs, NGK, with proper gap (0.28-0.31)
- 4 new Denso Spark plug wires
- New ICM/PTU, original Mitsubishi part
- 2 new Delphi coils installed as well
- New upstream Denso O2 sensor (was insane to get this thing out of the manifold from how stuck it was)
I will say it has been much better with those things replaced but its still there, especially on acceleration. Even very light acceleration it will skip badly. I do not know what else to check for. My OBD tool won't recognize the car for some reason (i think the car is too old for my ThinkDiag scan tool) so I cannot tell which cylinder is misfiring. I did check the cigarette lighter fuse, and its good (this controls OBD II power/communication I guess from what I have read).
From what I have researched, could possibly be injectors, injector resistor pack, ECT Sensor, Cam/Crank Position Sensors, vacuum leak or worst case the ECU. Engine Temperature gauge goes up to normal operation and stays there right below the halfway point so I am not sure its the ECT Sensor.
There is NO CEL that comes on at all, even when it skips, so I have no clue where else to look. I even unplugged the upstream O2 sensor to keep the car in open loop and still occurs. Any ideas would be helpful. My dad is going to try to bring his scan tool from work to check and see if it will communicate with the car so I can get a reading on the misfires hopefully some time this week.
Anything I miss? Should I check anything else while I wait for a scan tool?
Thanks for any input.
