I've been trying to tackle a odd misfire issue I've been having on my '89 M20. Happens randomly but very rarely.
First time it happened (9/2014)
Driving after about 20 minutes, then all of a sudden- loss of power, backfiring. Limped home about 15 miles and all of a sudden in 3rd gear- boom, started running perfectly. No CEL. Normal temp.
What I tried-
1. Seafoamed
2. New O2 sensor
3. Checked for vac leaks
Then it worked perfectly fine for 1,500 miles and about a year....not one issue at all. I thought it was just a faulty o2 sensor and fixed my issues.
Second time it happened (7/2015)
Started the same issue, about 10 minutes into my drive- back to misfiring. Let the engine cool down for an hour and tried to start it again, huge hesitation on startup, but eventually got it going. Hard to keep idle, limped all the way home again. Then boom, pulling into my driveway and it went right back to normal. No CEL. Normal Temp.
1. Installed new NGK copper plugs (old ones were OK and only a year old, had a bit of oil on them..but nothing horrible)
2. Ran compression- all good numbers in 160-165 range.
Other things that I have replaced:
-New Distro rotor, new cap, new wires.
-Rebuilt M50 injectors (and SSSquid tune) (All injectors are seated well)
-Verified all fuel connections, holds pressure. (all new lines, FPR, filter etc)
-AFM, ICV- all of the intake stuff has been cleaned and verified of working correctly
-No vac leaks. I've gotten a smoke test done at a shop and I do not have any issues.
-Battery Grounds are new
-TB, WP, Radiator- all that stuff has been replaced in the past year. I've done a lot of maintenance on the engine last year, the only thing I did not touch was the head/block/crank on the engine.
Just wondering what input everyone has for what I can check next. I never replaced my coil or CPS, not sure if they can go bad randomly. CPS is secure. As of now, whether or not it was a spark plug(s) that were bad- the car is running great as I type this.
Just want to see what else I can investigate, because I don't like how random this issue is and not get stuck somewhere one day.
Thanks!
First time it happened (9/2014)
Driving after about 20 minutes, then all of a sudden- loss of power, backfiring. Limped home about 15 miles and all of a sudden in 3rd gear- boom, started running perfectly. No CEL. Normal temp.
What I tried-
1. Seafoamed
2. New O2 sensor
3. Checked for vac leaks
Then it worked perfectly fine for 1,500 miles and about a year....not one issue at all. I thought it was just a faulty o2 sensor and fixed my issues.
Second time it happened (7/2015)
Started the same issue, about 10 minutes into my drive- back to misfiring. Let the engine cool down for an hour and tried to start it again, huge hesitation on startup, but eventually got it going. Hard to keep idle, limped all the way home again. Then boom, pulling into my driveway and it went right back to normal. No CEL. Normal Temp.
1. Installed new NGK copper plugs (old ones were OK and only a year old, had a bit of oil on them..but nothing horrible)
2. Ran compression- all good numbers in 160-165 range.
Other things that I have replaced:
-New Distro rotor, new cap, new wires.
-Rebuilt M50 injectors (and SSSquid tune) (All injectors are seated well)
-Verified all fuel connections, holds pressure. (all new lines, FPR, filter etc)
-AFM, ICV- all of the intake stuff has been cleaned and verified of working correctly
-No vac leaks. I've gotten a smoke test done at a shop and I do not have any issues.
-Battery Grounds are new
-TB, WP, Radiator- all that stuff has been replaced in the past year. I've done a lot of maintenance on the engine last year, the only thing I did not touch was the head/block/crank on the engine.
Just wondering what input everyone has for what I can check next. I never replaced my coil or CPS, not sure if they can go bad randomly. CPS is secure. As of now, whether or not it was a spark plug(s) that were bad- the car is running great as I type this.
Just want to see what else I can investigate, because I don't like how random this issue is and not get stuck somewhere one day.
Thanks!
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