R32 Gtr Lumpy Idle Help Needed Please!

[Japtastic-UK]

My GTR is running slightly lumpy on idle, when driving it's fine and pulls well apart from a slight mis fire at the top end.

Can any one suggest what this might be, I've tried cleaning the AFM's and cleaning the coil packs with the refurb guide, but no difference on either the lumpy idle or top end hesitation, are these connected?

More concerned about the lumpy idle at the moment than the hesitation...

On side note to try and adjust my high idle today I screwed the AAC screw in all the way but still the car idles about 1100rpm and I couldn't adjust this via the ECU screw either??

Another thing is that when bliping the throttle the car takes longer than I'd expect it to, to come back to it's base idle of 1100, it seems to hang around 1500 and very slowly back to 1100, the same when driving and coming to a stop pressing the clutch.

Hope you can help chaps

Cheers

[Ant97GTR]

Are you running an aftermarket ECU? If so it might be possible to adjust the idle via a tune.

As for the lumpy idle and hesitation....there are numerous things this would be.....first step would be trying to fix your AFM contacts via the tutorial on these forums as it is fairly easy to do and doesn't cost much. My second step would be to replace your coilpacks with either OEM or splitfire items as just cleaning your existing ones will not bring a dead one back to life - before you shell out on these items it might pay to get a mates coilpacks from a car you know runs well and replacing yours temp to see if it fixes the problem.

[Japtastic-UK]

Ok but could that really effect just the idle and top end and be perfect in between, surely if the coilpacks and AFM's were faulty it would be a problem through the rev range not just idle and top end? Some one has suggested an air leak at plenum, does that make sense?

[Ant97GTR]

Like I said there could be a range of things causing this but what I have listed are a common occurence in skylines. The AFM contacts fail and this is an intermittent problem...eg some people have experienced going over a bump and the car splutters before coming back to life. As for coilpacks I had this exact problem in my line a while ago and would only happen on full load at around the 5k rpm mark. Like I said it is fairly simple to grabs someones working coilpacks, put them in your car and then drive around the block to see if it fixes the problem.

[Japtastic-UK]

Thanks for your input It's more the idle I'm worried about at the moment, but will check the dry joints in AFM and coilpacks.

[Beer Baron]

quite possibly you have an air leak somewhere around the plenum. very common occurance on older 26's. symptoms are high idle (that cannot be made lower with factory adjustment) and occaisional missfire, and sometime popping/backfiring on gear change. unfortunately it's a pretty expensive fix to replace a $30 part as there is lots of labour involved in replacing the inlet manifold gaskets. when it's running just spray some water around the inlet manifold gasket areas and if there is a change you have an air leak.

[jantolis]

quite possibly you have an air leak somewhere around the plenum. very common occurance on older 26's. symptoms are high idle (that cannot be made lower with factory adjustment) and occaisional missfire, and sometime popping/backfiring on gear change. unfortunately it's a pretty expensive fix to replace a $30 part as there is lots of labour involved in replacing the inlet manifold gaskets. when it's running just spray some water around the inlet manifold gasket areas and if there is a change you have an air leak.

Ahhh this could be the cause of my idle being around the 1500-1700rpm mark. Everyone always suggested the AAC valve but never this. Might try this when i get my car back. How much would it cost to get this fixed if this is my problem???

[SLIPPERY]

Also sounds like the AAC is not stepping the idle down accordingly once you come off the gas. The 'motor' normally pulls the idle back down on idle but if your AAC is blocked or the spring is broken etc then this cant occur and the idle will hover a little higher for a period of time (or forever)

Have you taken off the AAC? there are 4 bolts that hold it on. Its possible to get in there near the oil filter and take it off in 30mins. Take it apart and give it a clean with some carby cleaner or a 50:50 mix of metho and kero.

cheers

[SLIPPERY]

to get an air leak fixed youre looking at $600-$1000 depending on whether the workshop wants to take out the master cylinder to get to the plenum. It adds up once they have to bleed the brakes again etc

[Japtastic-UK]

I'd be doing the work my self so not worried about labour cost, more my lower back pain!

Going to try spraying the gaskets today then off to get a cometic gasket and change if that's the case, cheers guys

Will let you know how I get on...

Edited October 10, 2007 by Japtastic-UK

[Abo Bob]

I would swap a known good set of coilpacks as your first port of call. If borrowed for free then it's a no money test which may just fix the hesitation and lumpy idle but probably not the high idle.

[femno]

Air leak for sure...gives you high idle and lumpy idle which means lean.

But it could also be a split hose or something. A stethoscope will help here, have a listen around.

If you pull apart the plenum and inner manifold etc, check them with a straightedge and make sure theyre straight, the gasket probably blew because of warpage, so if u dont want it to do it again check that. You probly wont need to machine the throttle plates but if you do make sure they get done all in one go so as they are the same thickness, not individually.

[Japtastic-UK]

I sprayed around the plenum/throttle bodies and sure enough the rpm of the engine raised each time I sprayed the carb cleaner on them, so it has to be the gasket/warping.

I would have thought the revs would drop though as my AAC screw was wound right in?

I have started removing the plenum now, it's very nearley there just a couple of bolts that hold the clutch lines to it which are so hard to get to it's unbelievable!

Edited October 10, 2007 by Japtastic-UK

[jantolis]

I sprayed around the plenum/throttle bodies and sure enough the rpm of the engine raised each time I sprayed the carb cleaner on them, so it has to be the gasket/warping.

I would have thought the revs would drop though as my AAC screw was wound right in?

I have started removing the plenum now, it's very nearley there just a couple of bolts that hold the clutch lines to it which are so hard to get to it's unbelievable!

How long is it taking you to do????

[gun32gtr]

yeh its meant to be a real prick isnt it

[Japtastic-UK]

It's a pain factor 9/10 my hands and wrists are in bits! It has taken me 3 hours today and bar 1 bolt it's off, so I should imagine another 3 and it will be back on, 6 hours labour in a garage round here would cost you $816 so well worth doing your self, it's not rocket science, at the end of the days it's just a few nuts and bolts, oh and the loss of some skin and back troubles

[R.3.2.G.T.R]

keep us posted dude.. might have to do this myself soon.. just wondering if its normal to have loud hissing noise near the intake plenum.. i think my gasket is gone as well..

[SLIPPERY]

no, thats not normal

[Beer Baron]

yay, beer baron picked it. I should charge for diagnosis. air leak is the easiest of all things to check, but for some reason people love swapping coil packs and afms, and AAC valves when all you need is a spray bottle with water or some carby cleaner and about 25 seconds of time to do it.

[jantolis]

yay, beer baron picked it. I should charge for diagnosis. air leak is the easiest of all things to check, but for some reason people love swapping coil packs and afms, and AAC valves when all you need is a spray bottle with water or some carby cleaner and about 25 seconds of time to do it.

Hey when i did clean out my AAC valve the idle did drop. It dropped from 2000 to 1500rpm. So it did sorta help. My mechanic is gonna do your test after i get my new turbos put in the car tomorrow. Hopefully that is the problem so i can finally get it fixed or atleast no what the problem is. At the same time i sorta don't want it to be it cause it sounds expensive.

Is it bad to drive around with a leak there?? Is there a quick intermediate fix for it?