Missfiring Rb26 - Need Advice On Problem Shooting

[Sarumatix]

I have an RB26 that started missfiring recently at the end of the 5000km of the current BCPR6ES11 (gapped to 1.1). I assumed the plugs were tired and pulled them out but bought BCPR6ES (these come factory gapped at 0.8mm according to repco). After changing the plugs the car has continued to missfire. The coilpacks are brand new genuine nissan units bought last year. Inspecting the old plugs there is definitely a slight fuel/oil residue on all of them although #5 and #6 appear a bit leaner (as is usual on RB26 plenum).

What should I check next? buy some 1.1 gapped plugs and try them?

[Sarumatix]

Tested alternate igniter that is definitely working fine and didn't clear it.

[Moodles2]

The smaller the gap, the easier is it to get a good spark (but at the slight cost of power), so the 0.8mm gapped plugs would have helped prevent the misfire if the 1.1mm gap was the cause of the misfiring on the old plugs. Just because the coilpacks were brought last year, don't rule them out.

We need more information like does it misfire while cold, or only when warmed up. Also does it misfire at idle or at high revs etc?

[Sarumatix]

Only missfires above around 4000rpm (urgh surely not coilpacks >.<)

haven't taken it past 4000 on cold to confirm but definitely does it while it's hot.

No missfire at idle

[SiR_RB]

Try running bcpr7es plugs

[sadr33]

Do you have $400 to burn on new yellow jacket coils? I have these and they work silky smooth with lots of room to spare.

Also hate to say it but you have never poured anything other than 98 RON fuel in there? I reccmend shell V power. Have you replaced you fuel filter?

Check your fuel pressures. It may be your pump your your fuel pressure regulator gone bad as well.

If I were you I would fit a new fuel filter, change to thicker oil like full syntetic 15w-50, 6 new yellow jacket coil packs and new plugs bcpr6es are good but try 7es as well. Fill up with Shell V Power. Reset ECU.

Thats a good start imo.

Edited November 4, 2012 by sadr33

[MrStabby]

Did reducing the gap have any noticeable effect?

Has there been any change in fuel economy?

Any more or less black smoke out the exhaust?

Any evidence of arcing on the top of the hole the plug sits in?

[Piggaz]

how's the coilpack loom? They get old and crappy. Replace that and try a known working ignitor.

[Count Grantleyish]

how's the coilpack loom? They get old and crappy. Replace that and try a known working ignitor.

I told him to check the loom, he's going to get another set of 1.1 gap plugs and check again.

[sadr33]

the worst thing he can do now is go 1.1. stay at 0.8 or lower to keep that variable off the table

[Count Grantleyish]

the worst thing he can do now is go 1.1. stay at 0.8 or lower to keep that variable off the table

What?

[sadr33]

What?

If hes diagnosing misfire issues going 1.1mm goes against narrowing down the problem. In less than ideal conditions 1.1mm gapped plugs can cause misfiring even if there is no other issues.

Why make troubleshooting harder for yourself. Bcpr6es are great for avoiding misfires as far as plugs are concerned IMO. Avoid anything -11. Or gap them yourself.

Edited November 4, 2012 by sadr33

[Count Grantleyish]

He've got BCPR6ES at 0.8 and it's still misfiring at 4k rpm, obviously it hasn't solved hence the thread.

[DVS JEZ]

Can u try another ignitor

[Sarumatix]

Yeah I tried another ignitor, same missfiring.

[Sarumatix]

Tried a set of known working coilpacks, exactly the same symptoms. I guess next step is to buy a couple of different sets of sparkplugs and try them out.

So I have tested alternate

Coilpacks

Igniter

I will try different

sparkplugs

- gapped back to 1.1

- bcpr7es

What else is left?

injectors

AFM

Loom - I find this extremely hard to believe as the one I have is very new without any dodgy clips etc

Edited November 10, 2012 by Sarumatix

[Moodles2]

Process of elimination:

- Borrow a known working AFM. If the AFM swap fixes the problem, then look at cleaning your AFM with a proper AFM cleaner and also resolder the cold solder joints in the AFM.

- Borrow a known working CAS

- Check timing with a timing light, the belt might have skipped a tooth or 2.

- Check fuel pressure. If the original pump is still in there, it's 18-23 years old and it's probably starting to struggle and needs replacing anyway. Walbro 255 or Bosch 040 are popular cheap pumps (just make sure to get a genuine one, forum sponsors are the best bet).

- Compression test

- Replace fuel filter

- Try unplugging the O2 sensor, it could be faulty but it's a long shot.

[Sarumatix]

Process of elimination:

- Borrow a known working AFM. If the AFM swap fixes the problem, then look at cleaning your AFM with a proper AFM cleaner and also resolder the cold solder joints in the AFM.

2 afms, big pain in the arse, easier to check with Consult (which i'll do)

- Borrow a known working CAS

good idea although i've never heard of a cas leading to 4k misfire

- Check timing with a timing light, the belt might have skipped a tooth or 2.

dun have, will have to get mechanic to check

- Check fuel pressure. If the original pump is still in there, it's 18-23 years old and it's probably starting to struggle and needs replacing anyway. Walbro 255 or Bosch 040 are popular cheap pumps (just make sure to get a genuine one, forum sponsors are the best bet).

bosch 044 which has been in for 7 years, guess it might be worth checking now.

- Compression test

mechanic.

- Replace fuel filter

did recently.

- Try unplugging the O2 sensor, it could be faulty but it's a long shot.

Never heard of o2 sensor fixing or breaking anything

ps. is it a bad idea to pull the plugs (bcpr6es) out and chuck them in another car? they have done about 20kms but i'm not sure if the washer is single use?