Rb26 Struggling To Pull Away At Low Revs

[Skysthelimit]

hey guys,

I am experiencing terrible bogging down at low revs in my R33 GTR V-Spec in the past 2 months or so.

eg. If I am wanting to turn left onto a main road, my car will struggle to bring up its revs. So it will hover around the 950rpm / 1000rpm mark for a considerable amount of time, before it builds up and I can take off.

Most of the time when it happens.. I will roll very very slowly, I can count from 1 to 5 at least before it starts to gather some revs and move. And it can happen at the lights at times, so I can imagine people behind me will be like get a move on, wtf is going on.

on maybe 2 occasions i felt a very slight 3 or 4 light jerks while it was happening. but mostly it is smooth just very slow.

I reved through to 7500ish yesterday, seemed to get up there fine, hit 12.1 psi

..if i launch off at around 1500rpm or 2000rpm the car will get away nicely.

Ok the numbers...

On my power FC it idles on 20 degrees timing, which will drop slightly to 18/19 degrees during the occurrence, when it picks up it seems to increase normally, no crazy jumping around..

I know idle is supposed to be 950 on the RB26, currently it is jumping between 871-929rpm.

The boost vac is sitting on -13 after a test drive.

Are these numbers about right or in the ok range? Or are there some discrepancies there that will give me a clue?

So far I have:

1) Replaced plugs with new spark plugs & fresh oil / oil filter change

2) cleaned up air pod filters

3) cleaned AFM with CRC CO Cleaner - stuff that leaves no residue

4) Replaced fuel filter

But none of these things have made any difference. Current tank has injector cleaner in it.

ohh.. and when bought the car, it did once and a while back fire, its become more frequent these days, happens when releasing throttle to change gears sometimes, or when slowing down and releasing the throttle.

In terms of mods, it is pretty stock, just running pod filters, front pipe back exhaust system, Power FC

Any help is very much appreciated,

Thanks

Edited August 7, 2011 by Skysthelimit

[_x_FiReStOrM_x_]

Checked for vacuum leaks?

[Skysthelimit]

thanks for the suggestion..

I've tried to check for them the best I can...

I have gone around and tightened up the all the hose clamps I can see.

I can not hear any leaking, all the hoses seem to be in good condition, its hard to listen for any leaks with the loud exhaust. Whats the best way to check for leaks?

Edited August 7, 2011 by Skysthelimit

[_x_FiReStOrM_x_]

Either pressurise the intake with compressed air while the engine is off and search for leaks. Or while the engine is idling, grab a can of carb cleaner (or similar) and spray around pipes, gaskets etc. The idle will change (raise) as the engine sucks in the spray.

[luvpsi]

either vaccum leaks or could also be clutch slipping. i had the same problem and i thought it was my terrible diff ratio until i tried to launch last night and car didnt go anywhere but clutch slipped

[Room42]

fuel pump on the way out?

[SargeRX8]

Cant be clutch as he said it was fine on launch. Also the clutch will slip, revs will rise, speed wont.

It the car coughing, spluttering, popping at all? My car would just not drive below 2krpm but was worse up top. I had two problems. Initial problem was failing fuel pump so I was lean popping everywhere. After that was fixed, I was running too rich and the plugs were fouling up.

Vacuum leaks are easy to find. Everything under the bonnet should sound smooth, no weird or unwanted sounds. Get a short piece of hose with dia. about 5 cent coin, put one end in your ear and the other go around the engine bay. It will help you hear a leak without hearing other engine noises. If you are in neutral and you raise the RPM to say 1100 does it hold? Or does it pop and choke on itself.

[Skysthelimit]

thank you for the suggestions guys ..

the car lets out two exhaust pops on gear changes.

..I don't think clutch, same reasons as SargeRX8 stated..

put on my other boost gauge, has different measurement for vacuum.. getting 300mmHg at idle is that low?

when decelerating gets to 500mmHg

if in neutral and hold revs at 1100 it holds fine, smooth, as well as any other revs I try in neutral

[lilcrash]

Comment removed, I miss read sorry

Edited August 8, 2011 by lilcrash

[_x_FiReStOrM_x_]

Hmm. Vac sounds a tad on the low side. Check your cam timing - just incase.

Edit - otherwise still sounda like a vac leak of some form.

Edited August 8, 2011 by _x_FiReStOrM_x_

[OMGGTR]

low compression ?

[snozzle]

f**ked/dirty afm(s) ?

[Pal]

mine is doing a very similar thing as well. get alot of backfires, changing gears it pops, decelerating and just touching the throttle will backfire and idle is very rough

doesn't have the get up and go as i thought a gtr would have.

got a funny noise happening under the bonnet as well but have put that down the a small leak in the BOV's when the car is not under load. same sort of mods as the op's as well.

car is running very rich at the moment so for a tune next week, hope that sorts out the backfiring and idle issues

[OMGGTR]

I had the exact same issues - low comp

[R.3.2.G.T.R]

what cat u running?

[Skysthelimit]

hmmm ok, thanks for the ideas guys

I'll have to get it checked out by a workshop I think, tried the hose to ear thing to look for vacuum leaks but couldn't find any.

Eric, who you booking it in with? I think I will get mine booked in also for a dyno tune and try and sort the issue out.

is normal vacuum at idle 500mm/Hg? I remember reading that somewhere, but not sure if I remember correct.

Edited August 9, 2011 by Skysthelimit

[Pal]

I go to Aaron at ITP Racing (used to be In tune Performance) in Bibra lakes(SOR), Its going in next monday, going to change the cat today to a highflow unit and will do a oil/spark plug change on friday. will also check all the pipes and vacuum lines

http://www.intuneperformance.com.au/