Cylinder 6 Misfire

Post by **red coupe89** » Mon Oct 17, 2016 9:31 am

heres the full story. car was running really good wed night. pulled battery to charge over night as start was a little slugish. hooked it back up thurs and now i have a misfire in cyl 6. checked my map and my tune and same on all maps. pulled plugs and it was wet, no visible oil. cleaned all plugs and installed in different holes. remains in hole 6. checked and changed coil pack and still no ignition. i have good fuel pressure, 42lbs. car is a 91 tt with 555 nismo injectors. dont know if there is something simple im over looking. going to check the ptu today and im assuming the CAS is good as its only on this one hole. any suggestions would be awesome, really dont want to have to do a compression test

Post by **elecfus** » Mon Oct 17, 2016 5:09 pm

a wet plug indicates that the fuel is not burning. a sooty plug means only some of the fuel is burning. combustion can take place from compression alone so a sooty plug does not rule out no spark.
what values did you read on your ohm meter for the coil packs? is there any corrosion on the connectors? it sounds like spark is not getting to the plug. so you need to run through checking the values of the coil pack, the wiring to the ignition module and the wiring from the ignition module to the ECU for cylinder six. if you check all these things and find no errors it might correct itself just from the movement in the harness. you would then need to run through the wires replacing them as faulty connections can fix themselves through jiggling.

there is also a minor possibility that the ECU may simply be broken and not able to send the correct signal to the ignition module.

there is also the possibility of a faulty injector spraying way too much fuel so you should check the resistance of the injector and possibly replace the injector o-rings as fuel may be leaking past the lower seal and get that injector flow tested if the other checks all pass. its much cheaper to have an injector cleaned and flow tested(about 10$) than to go replacing it.

Post by **evildky** » Tue Oct 18, 2016 8:28 am

Have you swapped the coil packs? You are on the right track moving the plugs, now do the same wiht the coils. If the problem persists at #6 then it is likely the ptu or the wiring.

Post by **red coupe89** » Thu Oct 20, 2016 1:39 pm

thanks fellas, i have tried switching good plugs and pack with the "bad hole". even did a compression test which thank sweet baby jesus came back at 140psi. to then i decided to ohm the injectors, 1-5 came in right around 11.2, number 6 1.0000 ie no value. make since seeing as like elecfus said. may be spraying too much fuel to ignite. O well, guess im going to call it a season and start tear down.....740cc here we come!!!!

Post by **elecfus** » Fri Oct 21, 2016 3:01 am

not sure what else you're running but general consensus seems to be upgrading from stock 370cc to 550cc is best.
beyond that people tend to find that the stock ECU tends to lack the capability to map it and runs into idling problems.
another option is to fit a second set of injectors.
which brand are you going for? look out for the fake ones. there are some companies that seem to sell high flow injectors with flow reports but the reports are bunk and they're second hand drilled injectors.

Post by **red coupe89** » Mon Oct 24, 2016 7:26 am

elecfus wrote:not sure what else you're running but general consensus seems to be upgrading from stock 370cc to 550cc is best.
beyond that people tend to find that the stock ECU tends to lack the capability to map it and runs into idling problems.
another option is to fit a second set of injectors.
which brand are you going for? look out for the fake ones. there are some companies that seem to sell high flow injectors with flow reports but the reports are bunk and they're second hand drilled injectors.

as i noted before i have the 555cc all ready. Im looking into the 740 from z1motorsports at the moment. tring to decide if i want to pull the cams and have them re-ground!

thanks!