Rb20det Dilema....

[r32line]

Hi Guys,

I have recently been having problems with my 32 gts-t. Basically under hard/full acceleration the car was flat spotting where it felt as though petrol was not getting into the engine properly around 4 - 5.5 thousand rpm.

First my mechanic tried a fuel additive which seemed to fix it but then it slowly returned. Then got the injectors ultrasonic cleaned. Again, seemed to fix it despite the fact that when i got it back the car had serious problems starting which it still does. 2 out of 3 times i hold it on start while its turning over and over and doesn’t come to life. After a second try it splutters into life. Now the flat spot has returned again.

It has cost $300 with additive and injector cleaning so far and back where i started. Also, it also does not idle well, specifically when pulling up to lights and selecting neutral while rolling to a stop the revs nearly drop to 0-100rpm. I stop and it comes back up, goes down, up.....

I have a feeling from what I have read on these forums that the problem may be related to the AAC valve but I would appreciate anyone who could offer any advice.

Thank you in advance!

[OGR88 R32]

i have this exact problem just dont have a flat spot the idoling shit is f**king anoying when your at lights! if i knew what the problem is i would let you know hopefully this thread will help me to

[n15m0]

chked ur fuel pump?

[r32line]

chked ur fuel pump?

Yeah that was one of the next things I felt could quite likely be a cause of the problem. But I was wondering if the AAC valve is (and im not sure if this is so) causing the idle issue could that have any relation to the flat spot?

[blind_elk]

You haven't stated if the engine has been modded in any way. Info like that is often useful in diasgnosing these sorts of problems.

Idle "hunting" is likely the AAC valve - it's the little cylinder attached to the back of the plenum chamber.

The flat-spot is totally unrelated to the AAC valve. It is likely the ECU is detecting "knock", which may be caused by a dying fuel pump. Get the car onto a dyno, with an AFR meter and a fuel pressure gauge.

[r32line]

Sorry about that, the car is very much stock other than:

3" turbo back X-Force exhaust system

Pod filter

Just to clarify the above post, what is an AFR meter? does this have to do with ariflow?

Edited October 22, 2006 by r32line

[insu]

AFR = Air Fuel Ratio.

There isn't a meter for this in the car.

The car monitors Air flow = AFM (Air flow meter)

and from this and other factors (tps etc) determines how much fuel to put into each cylinder at various revs/load etc.

The car also has a o2 sensor which tells the car essentially if the car is running rich or lean.

If you want a proper AFR you'll need to get a wide band AF gauge and probe. Very good tuning tool, lets you know exactly whats going on with your AFR's.

You know when you see people getting their car tuned on a Dyno, and they tuner's got a probe sticking in their exhaust? This is what that is.

Sounds like your problem is fuel issues, either too much or too little.

Generally the more mods you do to a skyline the richer they run. Richer=safer (away from detonation) but also means retarded as far as power use goes, and fuel economy goes down.

It could also be fuel starvation= Ie, dying fuel pump, blocked fuel filter etc.

This is the most dangerous of all senarios, if this is the case, get it fixed soon.

[samdasurfinman]

Personally, I'd replace the fuel filters first. I had that exact problem and replacing the filters totally fixed it.

[r32line]

Thanks for the replies.

It's all very confusing. Im a bit worried now, I will have to minimise my use of the car from now on cause I am really busy with uni/wrk so cant get it looked at atm. The only day I have to use it is wednesdays, every other day i can get lifts/use another car or p/transport.

At least I know a few things it could be know. I hope i can find out for sure what the problem is.

[r32line]

Just to add to that,

When I just drive the car normally (as in not rev beyond 3,500rpm) it is 100% fine and drives smoothly and without problem, other than the issue of getting it started... So this wednesday and next I assume that it wont be doing any damage driving like this??

[Guest tosboost2]

ok to start i know on this forum that this guy says do this, and another guy says do that. so i dont care if u listen to what i have to say

but anyways i had the same problem with my 32.

i spent 600-700 bux diagnosing the problem and changing things, taking the car places etc.

it ended up being my afm was dead, so i got a new one, and the seal around my blow off valve was busted, i dunno how that made much difference but i fixed that, i still have a few problems but only when the cars cold, which is the cold start valve. and seeing as i cant find another one ill have the problem for a while.

find someone else with the same afm as you and just swap them over and see if that helps

[r32line]

ok to start i know on this forum that this guy says do this, and another guy says do that. so i dont care if u listen to what i have to say

but anyways i had the same problem with my 32.

i spent 600-700 bux diagnosing the problem and changing things, taking the car places etc.

it ended up being my afm was dead, so i got a new one, and the seal around my blow off valve was busted, i dunno how that made much difference but i fixed that, i still have a few problems but only when the cars cold, which is the cold start valve. and seeing as i cant find another one ill have the problem for a while.

find someone else with the same afm as you and just swap them over and see if that helps

Thanks for your help, my mate has a 32 gts-t like me, so I can try that then and ill put in a new petrol filter if that doesnt work and see...

[r32line]

Well for those who are interested... PROBLEM SOLVED

After being introduced to a friend of a friend, we got talking, and I found out he owns an r32 gts-t also, and is a mechanic!! He had rebuilt his rb20det and knew a lot about them.

Took my car to him and he discovered a pipe connected to the fuel pressure regulator was split in 2 places and barely hanging on. Replaced that and he raised the idle and it was fine, revvvvs out beautifully and sits perfect at 800pm at idle and doesn’t fluctuate.... all this fixed for next to nothing, meaning the $300 spent to date was wasted... at least its fixed !!!!!

[WazR32GTSt]

which "pipe"

can you put up a pic of an engine bay and point to it?

cheers,

Warren

PS did it also help with the starting issue?

[r32line]

which "pipe"

can you put up a pic of an engine bay and point to it?

cheers,

Warren

PS did it also help with the starting issue?

Yeah its pissing down outside now, but next available chance i will take and post pic, and yes it had serious issues starting sometimes, others it would be fine, but more often than not id have to try 2 or 3 times... all good now

[WazR32GTSt]

is it the pipe with the arrow, or another pipe in that pic?

.. just a pic i found doing a quick search on SAU, sorry if its someone's car in particular!

[r32line]

is it the pipe with the arrow, or another pipe in that pic?

.. just a pic i found doing a quick search on SAU, sorry if its someone's car in particular!

Nah its at the other end of the engine, near the aac valve, ill post up tomoro....

[WazR32GTSt]

how'd you go with that picture mate?

[r32line]

how'd you go with that picture mate?

Soory for the delay, been busy, but im pretty sure this is the small pipe that was replaced, i was eating at the time he took it off so i didnt 100% see....

[grigor]

Vacuum pilot control to fuel damper so just another vacuum leak.

Makes you wonder about the condition of the fuel pressure hoses.

Pays to replace all hoses, they're getting old.