R32 gtr misfire

[cole__gtr]

So guys I've been trying to get this skyline running right since the day I bought it which was probably over 6 months ago, it started out with a slight misfire that you could only hear it if you listened closely, and stayed that way for a long time, the car also bogged down on full throttle and ran rich as hell, one day I drove it out the shop and whenever I have it gas the car would just not want to move at all, it kind of tried to but wouldn't really do anything but coast with the clutch out, so I got the car towed home on a deck and I pulled my fuel pump out and thinking that was the issue I pulled the wiring apart and resolded the wires for the walbro plug to join to existing eom wiring harness, car still wouldn't run right for awhile eventually it started to actually rev up but had a terrible misfire from then on, I've replaced coil packs, cas, coilpack wiring harness with prang new parts and a known working used ignitor, car still has a bad misfire in kind of stuck and getting pissed off with this car to the point I want to drive it onto one of my fields and burn it down, I've thrown a lot of money into it which is stupid but that was the only way I could get known working parts because I don't really know anyone with a skyline around saskatoon, so does any of you guys have any suggestions for me to why this car is doing this? Any help would be appreciated, I've also changed spark plugs 3 times and resolded mafs, my only next suggest could be injector problem? Or ecu?

[cole__gtr]

Help anyone?

[Micho]

Possibly it's the tune on the ECU? Stock?
What type plugs are using? Are they gapped properly?
Check for vacuum leaks? MAF/Intake/Intercooler piping?

[Skym]

Injector leaking can cause missing problems, which is common on high km RB engines.

Sometimes it can be a leaking headgasket (usually 5th, 6th cylinders).

Sometimes can be leaking intake gaskets (upgrade to Tomei or similar intake gaskets) making engine run very lean, which would make ECU engage knock maps. This is common on any RB engine.

Sometimes can be the engine running rich due to lazy o2 sensors making engine run too rich for too long. Usually get popping sound from exhaust when that happens.

Sometimes can be bad batch of gas (does happen) or octane of gas is too low and ECU is detecting knock, switching to knock maps which make engine run richer, pulls ignition timing.

Sometimes the CAS is set incorrectly.

Sometimes the cam timing is incorrectly set.

Sometimes can be the ignition module

Sometimes can be a faulty TPS making engine run suddenly lean (lean missfire).

Sometimes can be airleak behind MAF's making engine stutter (similar to missing coilpacks). Or a intake airleak before MAF making ECU hit the boost cut.

[cole__gtr]

Thanks for the suggestions skym, it is 6th and 5th that is the cylinders that are missing, I got a timing light and I'm going to check my timing when I get a chance to get to my shop. @micho I've gapped plugs to .08 I think it is and I'm running stock ecu, I've checked all intercooler piping

[bobbo]

It's does sound like an issue with charge piping (ie. leak) there are quite a few places to check and removal of the front bumper is necessary to check properly.
Good luck and keep at it. It'll be worth it when you solve the problem.

[Dragon Humper]

This sounds an awefull lot like a cam gear skipped a tooth as well, what does the belt feel like...loose?

If it is an intake leak after the MAFs, try unplugging them and start the car, it should get better. The ECU will default to limp and stop trying to make sense of goofy looking MAF readings.

I would do a quick compression test while you are at it.


Jon.

[cole__gtr]

Would low compression be the cause to a misfire?

[bobbo]

It would be consistant and you'd be blowing a lot of blue smoke especially under acceleration.

[cole__gtr]

Ok my car doesn't blow blue smoke but I didn't do a compression test and cylinder 6 was at 100 and 5 was at 120

[Dragon Humper]

Uh oh.....thats not good. Sounds like fried rings or a busted ring land from leaning out. Hope you got the car cheap because a rebuild is in your future.



Jon.

[cole__gtr]

I did do a compression test

[cole__gtr]

I think it's the rings I dropped a cap of oil and it raised the compression up, I got it some what cheap but I've also put money into suspension etc

[Skym]

Do a leak down test, as it can sometimes be rings, valves or headgasket. Usually headgasket if 5th, 6th cylinders (it's where the heat builds up near firewall and head warps, crushes the headgasket seal around cylinders thus causing the leak, which creates the missing).

Engine might have overheated in the past, so clean, check deck of block, head for cracks. But if doing the headgasket, might as well do a refresh on engine (rings, bearings, etc), as it's not much more to refresh engine vs just doing the headgasket.

Another option (if car is used for a daily driver) is fitting another second hand engine while rebuilding the one you have.