6th Cylinder Not Firing

[MattyP]

A while ago the revs in my GTR jumped 400rpm (to 1900) and never went down.

Did some searches on here (AAC and other things) and tried figuring out what it could be.

Changed the spark plugs, no change

Then a mate came around and did some tests, and then we unhooked each coil pack (one by one) and found the 6th one to be the cause.

Bought some JJ coil packs, and changed them all over this morning to find the problem is still there.

I'm going to try another coil pack harness to see if that is the problem.

Can anyone suggest anything that might fix or tell me what the problem is?

(as for mods on car if it helps: 2530s, HKS F-Con Pro and usual basic stuff)

[MattyP]

I just had someone look at the car and they said quiet possibly the intake manifold gasket could have blown, which is resulting in a leak of air at idle and causing the RPM to go higher.

But then I don't understand why that would create the 6th cylinder not to spark :S

Is it common for the coil pack harness to breakdown?

Also, I've found the engine to get very hot pretty quick however all temp gauges etc are showing normal operating temperatures.

[MattyP]

Had a workshop look at car late last week.

Did compression test = all good

Disconnected the 6th injector and the revs dropped so I would assume that its getting fuel to the engine.

All coils are getting spark etc.

Any ideas what else it could be?? I've search the forum a million times and none have the answers.

[Amec]

so has no 6 come back again or ???

[MattyP]

Sure hasn't...

Swapped over igintion amplifiers too, no change

Regapped spark plugs, no change

Taking it to Autobahn tomorrow morning (of all places), and the guy there is going to try a stock 32 GTR ecu on it and see if the problem is still there and god knows what else. The guy there has 3 GTRs (two 32 and a 34) and said it could quiet possibly be the knock sensor :S

After that, may take to All Star Garage..and if they seriously can't figure it out I'm just gonna leave it until I can be bothered going into the engine deeper to see if it could be something else.

Edited October 29, 2008 by MattyP

[lunjiaow]

I seem to be in the same boat as you are MattyP.

Have you tried the CAS?

My one misfires at idle and drops the 6th cylinder. But when driving its Perfect.

Im sure its not the head gasket. I've replaced my one last time and problem was still there. I fixed the problem a long time ago

with a new CAS and Ignitor Pack. Problem has come up again recently. I tried chaning CAS and Ignitor Pack but no luck.

Some people reckon it might be the injector rail slightly bent, thus leaving a gap for an air leak. But i highly doubt it.

[DAS KAMU]

Sure hasn't...

Swapped over igintion amplifiers too, no change

Regapped spark plugs, no change

Taking it to Autobahn tomorrow morning (of all places), and the guy there is going to try a stock 32 GTR ecu on it and see if the problem is still there and god knows what else. The guy there has 3 GTRs (two 32 and a 34) and said it could quiet possibly be the knock sensor :S

After that, may take to All Star Garage..and if they seriously can't figure it out I'm just gonna leave it until I can be bothered going into the engine deeper to see if it could be something else.

allstar in geebung?

[tacker]

Had a workshop look at car late last week.

Did compression test = all good

Disconnected the 6th injector and the revs dropped so I would assume that its getting fuel to the engine.

All coils are getting spark etc.

Any ideas what else it could be?? I've search the forum a million times and none have the answers.

Mate it has to be a vacum leak your engine is getting unmetered air from somewhere which is not a good thing at all. Run your engine and get some airo start / WD 40 or something and spray it around the intake side of the engine when it increases rpm when you spray that should lead you to the vacum leak, worth a try at least.

[MattyP]

Apparently air leak has been searched (by two workshops) and failed to show any results around the intake. Though will ask for it to be checked again tomorrow.

A guy in the UK had the same problem with his RB26 powered Silvia, and turned out the PowerFC became faulty. He had changed everything I have done above.

What's CAS?

[GTRsean]

Apparently air leak has been searched (by two workshops) and failed to show any results around the intake. Though will ask for it to be checked again tomorrow.

A guy in the UK had the same problem with his RB26 powered Silvia, and turned out the PowerFC became faulty. He had changed everything I have done above.

What's CAS?

CAS is the Cam angle Sensor, this is the round device at the front of your engine on the cam cover. It sends the signal to the igniter and computer when to fire a cylinder and also ignition timing.

[lunjiaow]

Hmmm power fc... i happen to have one too.

With one cylinder down does it make your car hard to start?

[MattyP]

Nah, starts up pretty easy which surprises me as I know you can't start your car up on rotational idle (not that I have it)

CAS sounds like something to look into also. Probably only way to test is to replace it with one that is known to be working :S

[blind_elk]

This is VERY confusing. What exactly is the problem? Is it the high idle, or is it #6 cylinder not working? (you shouldn't get high idle with a dead cylinder).

Then you're saying idle dropped when you disconnected #6 coil. But it should have dropped when each coil was disconnected. That says #6 is still working, yet you stilll have the problem.

Maybe I'm just getting old, but it all makes absolutely no sense.

[MattyP]

Car has a high idle AND #6 isn't working. Don't ask me why, however if I was to assume I would think that since the car would be running lean its reving the engine higher to make up for the lost fuel :S

I said the idle dropped when we disconnected #6 injector, not the coil pack. The idle didn't drop when we disconnected #6 coil. (see post 1 & 3)

Had a call from Autobahn today and they told me they replaced the throttle thingy on the car (something that Cypher told me to replace), and they said they dropped the revs to 1k and the car seems to drive fine.

I loved the fact he told me he didn't boot the car, but it 'launched really well' and seemed to come on boost pretty smooth lol. I did highlight the fact that even though he dropped the revs, that there could still be #6 not there as well so he's double checking that for me. Unfortuantely I won't know what the deal is till tomorrow afternoon.

[blind_elk]

I said the idle dropped when we disconnected #6 injector, not the coil pack. The idle didn't drop when we disconnected #6 coil. (see post 1 & 3)

Sorry, but that DOES NOT COMPUTE!. You need fuel and spark to produce power. Take one away, and you get nothing. So how can removing fuel cause the idle to stutter, but removing spark doesn't affect idle at all? If the coil isn't firing, then it won't matter a cracker if you have fuel or not. So disconnecting the injector won't have any effect on the idle.

[MattyP]

Well that's exactly what I thought too...so its just as confusing as it is for you as for the workshops looking at the car.

The guy apparently is going to try his harness from his 32 GTR (modify it a bit too) and see if that changes anything.

[R334door(s2)]

similar thing is happening to my mates rb20 we checked the ignitor loom ignitor pack coil packs are fine plugs are fine even swapped over parts with another mate to rull out the other stuff just no spark could be past the ignitor this is where i get worried but we have it booked

in at my mates work shop for wednesday thursday they should sort it out ill let you know what we find it may help you with your problem.

just try to narrow it down so check and recheck etc

[MattyP]

FINALLY GOT THE ANSWER to what's wrong!!

Crack in the inlet manifold gasket around #6, something that was first suggested to be the cause but proved not to be the case until now.

How easy is it to change this? Is it best to leave it to the pros as they've told me (and I've been told) its a pretty labour intensive job.