Rb26dett Idles Rough (260rs)

[BoostedBarge]

Hi everyone,

I recently purchased a Stagea 260RS Autech Version. I am after your advice on the idle. It seems to idle a bit rough, like it has a bit of a miss. It drives perfectly smooth and seems to go quite hard. The day I drove the car out of the compliance centre it developed a miss after about half an hour of traffic driving. I replaced the plugs and I haven't had this problem again, but the idle still seems a bit average. Often when I start the car it will idle at 600rpm. Sometimes it will sit at 900rpm and even above 1000rpm (possibly cold start). The A/C also makes things worse as expected.

I have plugged Consult in and it reports no faults. I shut down each cylinder at a time to try and find a culprit, but I couldn't really put it down to a single cylinder, they all have a similar affect. I thought that maybe the cause is a boost/vacuum leak, but listening around the engine I can't hear hissing and it seems to boost fine. In Consult I went into idle adjust mode and the revs dropped even further (~500rpm). I tried playing with the idle valve and base timing settings in Consult test mode, but this had little affect in terms of improving things. I am going to get a timing light off a friend to check base timing is set correctly.

Does anyone have anything else I could try or any common faults? I have checked the compression and it was reading high 174 lowest, 182 highest. I suspect that the gauge was faulty, but at least there wasn't a single cylinder that was down. The engine looks dead stock and has 72000 on the clock. Or perhaps a lumpy idle is common on an RB26?? (I haven't heard any running on a stock ECU)

Thanks heaps,

Simon

[ssshonky]

you sure it doesnt have crazy lumpy cams in there?

to me - and I will admit - I have not read your post in full detail - but sounds like a dirty throttle body or a gunky idle air control valve.

if you put aircon on - does it settle down ? cause the AAC valve *aircon or auxilary air control ) should pump the idle up a bit to compensate for aircon compressor load

[BoostedBarge]

Thanks for your reply.

I doubt it has lumpy cams. The whole car looks pretty much stock, except for exhaust.

Turning the A/C on does not seem to improve the idle and sometimes makes it worse.

[Ki_spirit]

Is there a seperate valve responsible for the rpm increase on cold start? Maybe cleaning the AAC valve will help regardless, I am yet to do mine.

[BoostedBarge]

Well I tried out some other Consult software yesterday. Nissan Scantech http://www.techdiag.co.uk/obdscantech/web/pg002.html

I am now a bit closer to putting my finger on the problem. It will do a balance test where it shuts down each cylinder and measures the average RPM and then gives a report on the RPM dropped for each cylinder. Every cylinder dropped by 100rpm or so, except number 2, which raised the RPM very slightly (dunno why)! So it looks like cylinder 2 has a miss at idle. I'm gonna change the coil pack with one of the other cylinders to see if I can pin in on the coil pack.

Other things I noticed:

-One O2 sensor seems be a lot less responsive than the other. It takes a while after the engine has warmed up for the O2 sensor voltage to move much and even then it moves half as much as the other, so I think it may be on the way out. Anyone know a good place to get a cheap replacement?

-Another strange idle problem, when you slightly raise the revs and then release the throttle the revs will first raise higher and then fluctuate up and down a few times before coming steady. I think this may be a sticky AACV valve. I think I will fix the misfire first, before I investigate this one furhter.

[BoostedBarge]

I did some more work on this last night and swapped coilpacks 1 and 2. The problem did not change, it is still cylinder 2. So I know it's not a coil problem.

I pulled out the spark plugs on cylinder 1 and 2 and compared. I found that the cylinder 2 plug was a lot blacker around the white ceramic insulated part. So it's either running rich or not firing properly. I'm thinking that maybe the injector could be partially blocked. The car is a fresh import (was imported November last year and had driven <100km before I bought it), so who knows how long it has been parked with old fuel in the tank. I bought some injector cleaner last night. Lets see if that helps things...

[BoostedBarge]

Well, I put the injector cleaner in and I'm about half way through a tank and the miss is still there. It seems worse when the car is cold. When it's warm is idles fairly well most of the time. When cold it sits at around 600rpm. The air conditioning makes it worse, too. Does anyone have any ideas of what else I could look at? So far I've replaced spark plugs, swapped coil packs around (on Consult the problem stays with cylinder 2) and put injector cleaner into it. I'm tempted to swap injectors with one of the other cylinders to see if the miss is cause by the injector.

Cheers,

Simon

[pipster11]

i'd be swapping the injectors over and possibly getting a noid light to test out if the injector is getting a pulse.

i'd also be getting some throttle body cleaner and give everything a good clean

might as well clean ur maffs whilst ur there

[Ki_spirit]

ok, this is going to sound stupid - but possibly check the wiring loom at cylinder 2 where it connects to the coilpack. Probably not the case, but atleast you can then rule it out.

Have you done the epoxy thing to your coilpacks? - I'm not sure if the heat-cracking phenomenon occurs on rb26's but I will ask anyway, (as they do in rb25's, so I thought why not )

All the best finding the prob.

[BoostedBarge]

Yeah I've checked the wiring around cylinder 2 and it's all fine. I'm not familiar with the epoxy thing. I'll have to do a search of the forum. RB26s have the same coil packs as RB25s (series 1s, not sure about series 2), so it should be prone to the same problems. It seems that the problem is not coil pack related, since I swapped the coilpack with cyl 1 and the problem was still there on cyl 2.

It may be just me, but I think the idle may be improving. One of the main things I'm noticing now is that when it's cold it idles at about 600rpm and when the throttle is opened and then released it will hold the revs at like 1500rpm before eventually coming down. My wife says it's kind of annoying, it sounds like you are slipping the clutch. Maybe this problem is unrelated to the misfire and perhaps due to a sticky idle control valve.

I just realised that this topic is in the wrong section. Sorry about that. If any mods can move it for me, then please do.

ok, this is going to sound stupid - but possibly check the wiring loom at cylinder 2 where it connects to the coilpack. Probably not the case, but atleast you can then rule it out.

Have you done the epoxy thing to your coilpacks? - I'm not sure if the heat-cracking phenomenon occurs on rb26's but I will ask anyway, (as they do in rb25's, so I thought why not )

All the best finding the prob.

[BoostedBarge]

Latest update on the idle problems:

Last night I got home from a short 5 minute drive to the shops. I let the car idle on the turbo timer for a minute. All of a sudden the revs lifted for no reason. It seemed to sit at around 1500rpm and fluctuate around this point by 500rpm or so. It sounded like someone was sat in the car playing with the throttle! My wife said that she has seen this happen before, when sat at traffic lights or whatever. Any idea what it might be?

My ideas are:

-Sticky idle control valve

-The injector from cyl 2 is still a bit gummed up, but the injector cleaner is starting to help causing the injector to fire properly every now and then at which point the idle control is wound right up by the ECU idle control and causes the revs to raise dramatically (yeah that one's a bit out there).

When I get a chance a will swap over that injector with another cylinder to try and see if I can prove the problem is due to the injector. Also, one of the O2 sensors is a bit lazy, so that's probably not helping the cause..

[1centgts4]

could try checking throttle body seals, rough idle can be caused by a stuffed seal or 6.

[BoostedBarge]

Cool, thanks for replying. I'll look into that. I'd imagine it's not a quick job to check the throttle body seals. I'll look into it..

Cheers