[solved] on going cylinder 4 misfire

jesus

jesus

Greenie N00B Member
Greenie Member
For the longest now ive been having a cylinder 4 misfire that will come and go out of random. Ive gone through and replaced a ton of hardware( spark plugs/coil packs/wiring harness/fuel injectors and seals/ fuel rail and injector harness/) only time I've noticed a difference of the problem becoming less frequent is when gaping cylinder 4 to around .23-.25 anything higher then that and it seems to just hate it and starts acting up. At a loss here and any info or advice would be greatly appreciated. Data logs can be provided as well if needed.
 
Compression and leak down test is next.
 
jesus said:
For the longest now ive been having a cylinder 4 misfire that will come and go out of random. Ive gone through and replaced a ton of hardware( spark plugs/coil packs/wiring harness/fuel injectors and seals/ fuel rail and injector harness/) only time I've noticed a difference of the problem becoming less frequent is when gaping cylinder 4 to around .23-.25 anything higher then that and it seems to just hate it and starts acting up. At a loss here and any info or advice would be greatly appreciated. Data logs can be provided as well if needed.
Click to expand...

You've done the "bunny hop" with the plugs and boots and kept track? ie: plug from 4 goes into cylinder 2, boot goes on cylinder 3 and make sure the problem stays on cylinder 4?
 
Finally got some free time and was able to find, after a some diag the root of the issue, the ground wire pin for cylinder 4 was completely pushed into the connector causing it to short out the spark. I went ahead and changed out the engine harness with one i had laying around and it hasn't misfired yet ever since then. Also in response to the plug gap i meant .26

Compression 165-150
1 - 160
2 - 165
3 - 150
4 - 150
Leak down 5-15%
1 - 10
2 - 5
3 - 15
4 - 10
 
Last edited:
.26" is waay to big, should be .026-.028"

Glad the misfire is gone, engine seems to have had better days
 
update to this whole mystery it ended up being a improper seating intake valve. I ended up putting some work into the head getting new oem valves, crower springs & fresh seals since then no more cylinder 4 misfire. even went ahead and slapped on the BNR S4 i had waiting around.
 
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