Car has been running great since last summer. Had issues with a vaccum/oil leak last year that caused it to not run but got that sorted and it ran great since.
It's slowly developed a stumble anywhere from 2500-4000 RPM's. Cruising at lower RPM's it runs fine. If I go from a stop and really hammer it from 1st-3rd gear, revving it way up, it runs and pulls smoothly and strong (for an m20
). Most of the time the stumble occurs while driving normally/spirited in that 2500-4000rpm range. Stumbles, bucks, etc. it used to go away when the car warmed up, but now it's doing it consistently. No check engine light is on.
The only thing left to try that I can think of is something with the fuel injectors or fuel rail.
New parts/work done to the car:
- Stock M20 with cold air intake, chip, and tune. Co was set at the time we
tuned it and it ran excellent.
- New FPR
- New Fuel pump last summer
- New Fuel Filter
- Remanufactured bosch AFM
- New Bosch cap and rotor
- New plug wires (2 years ago)
- New plugs (last year. I pulled them 2 weeks ago and they looked good)
- New Crank sensor last year - this was very dirty, cleaned it up and didnt
change anything. Planning on checking the wires again to see if there are
any cracks/breaks.
It's slowly developed a stumble anywhere from 2500-4000 RPM's. Cruising at lower RPM's it runs fine. If I go from a stop and really hammer it from 1st-3rd gear, revving it way up, it runs and pulls smoothly and strong (for an m20

The only thing left to try that I can think of is something with the fuel injectors or fuel rail.
New parts/work done to the car:
- Stock M20 with cold air intake, chip, and tune. Co was set at the time we
tuned it and it ran excellent.
- New FPR
- New Fuel pump last summer
- New Fuel Filter
- Remanufactured bosch AFM
- New Bosch cap and rotor
- New plug wires (2 years ago)
- New plugs (last year. I pulled them 2 weeks ago and they looked good)
- New Crank sensor last year - this was very dirty, cleaned it up and didnt
change anything. Planning on checking the wires again to see if there are
any cracks/breaks.
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