Engine Works Well At High Boost

[ksx]

Hi all,

Having problem with my R34 GTT:

Engine goes very rough at low boost levels, for instance at idle speed and when revving without any gear engaged to about 2-3000rpm it “coughs” and seems to have very rough hiccups all the time, if you know what I mean…? At high boost levels it runs like a dream though, no problems at all to rev to the limiter and there’s plenty of power without delay or hesitation.

So, wtf!? What do you reckon?

Stuff on the car: pod filter, fmic and 3” cat-back.

Also, thinking about leaving Sweden to move to Australia with my girlfriend. Do you recommend it?

[Hanaldo]

Also, thinking about leaving Sweden to move to Australia with my girlfriend. Do you recommend it?

Yes!!

Has your car been tuned or is it stock ecu?

Does it happen while cruising/decel or on acceleration?

[ksx]

hehe, ok! That's all I need to hear, you just made me decide to move there

Will need to start looking for jobs first. Thinking about Holden, where's the development site situated?

The car runs with stock ECU. It's all stock except HKS pod, FMIC, HKS cat-back and HKS ssqv.

It happens while cruising, anytime the boost is gentle and even. Decel or acceleration works just fine.

[Ultimategtr]

Might be that you're running too cold plugs. What plugs are you running?

list of mods?

[Hanaldo]

hehe, ok! That's all I need to hear, you just made me decide to move there

Will need to start looking for jobs first. Thinking about Holden, where's the development site situated?

The car runs with stock ECU. It's all stock except HKS pod, FMIC, HKS cat-back and HKS ssqv.

It happens while cruising, anytime the boost is gentle and even. Decel or acceleration works just fine.

I've changed a life. My job here is done

So when cruising you would be driving on vacuum not boost yes? On boost you would be accelerating. Does it hunt at idle, like rev up and down? And is it more pronounced when the car is warm or is it exactly the same when it's cold? Sort of sounds like it could be a problem my mates R32 had, was effectively a vacuum leak. The air regulator was stuck open, so when the car was cold it ran fine but when it warmed up the air regulator was still open and the car was getting too much air. Ran fine when you were accelerating, but trying to cruise it would just stutter and jump, etc.

Could also be a problem caused by that atmo bov you have.

[Trozzle]

YES COME TO AUS! Bring MORE swedish girls with you too! (my GF is Estonian, so if we got more or them/Swedes in this country, we'd be happy men)

Could be the stock ECU is gumby, or the AFM is fail....sounds kinda like it might be running excessively rich, but once the airflow climbs up with more boost, it compensates and evens out...

[Birds]

Bring a Swede for me they are always good value

[Trozzle]

great value! can't wait to hit the place up next year with the missus....oh lawd

[ksx]

Might be that you're running too cold plugs. What plugs are you running?

list of mods?

Actually don't know. Havn't checked since I bought the car, the plugs were brand new then. Will check tonight or this weekend. Temp grade 6 is standard, right? With my mods which I've already listed above, should I go for 6 or 7?

I've changed a life. My job here is done

So when cruising you would be driving on vacuum not boost yes? On boost you would be accelerating. Does it hunt at idle, like rev up and down? And is it more pronounced when the car is warm or is it exactly the same when it's cold? Sort of sounds like it could be a problem my mates R32 had, was effectively a vacuum leak. The air regulator was stuck open, so when the car was cold it ran fine but when it warmed up the air regulator was still open and the car was getting too much air. Ran fine when you were accelerating, but trying to cruise it would just stutter and jump, etc.

Could also be a problem caused by that atmo bov you have.

Yeah, you're right, vacuum not boost, sorry. I find both the technical issues and the language quite hard you see...

The rpm stays quite even at idle, but not as even as it should be I guess. It "huffs and puffs" quite much at idle, and it's no difference between hot or cold engine. Sounds as your friends R32 had the same probs as mine. Will check the air regulator. One question though; where's the air regulator and how do I check it?

In what way might the bov be the thief in this drama?

Could be the stock ECU is gumby, or the AFM is fail....sounds kinda like it might be running excessively rich, but once the airflow climbs up with more boost, it compensates and evens out...

What I've heard before the stock ECU would cope with the mods I've done already (pod filter, fmic, cat-back, ssqv)? Do you have other experiences? If it is what you say, then a new ECU is the only solution I guess..?

How do I check the AFM? Already pulled out the AFM cable when engine at idle and it started to run really bad, almost died. That means the AFM works, at least a little bit? Can I clean the AFM somehow?

Thanks for your feedback! Will have to bring a lot of swedish girls to compensate!

[Hanaldo]

Air regulator is located near the plenum, follow the vacuum line that is Tee'd into the hose coming from the AAC valve.

Bov could be the culprit as it is atmospheric, it releases the air into the atmosphere after the AFM, causing the ecu to over inject and run rich. But bov's usually cause problems on decel, so it doesn't sound like this is the cause of your problem...

[ksx]

And is it more pronounced when the car is warm or is it exactly the same when it's cold?

Hey again,

just realized that the problem is much worse when engine's warm! Does that make it easier to say what's might be wrong?

Thanks

[Hanaldo]

Definitely sounds like air regulator then mate, get that checked out. It's a very simple mechanical valve that can break very easily.

[ksx]

Ok, thanks mate! Will have to check that out then. Just to clearify: Air Regulator is the same thing as AAC valve, right? Or am I reading the service manual wrong?

This Air Regulator, does it have a part number and how much does it cost approximately?

THANKS!

[sh@un]

plugs!

check the plugs before doing pretty much anything. it's most often the reason for this sort of thing

[ksx]

Problem fixed!!

Vacuum hose cracks (one was completely spilt all the way along the hose!), useless plugs (original modified to 0,5mm!) and crack angle sensor set to 27 degrees!!

Air regulator, AFM and ignition coils works just fine.

New spark plugs, rubber hoses and crack angle back to original 15 degrees - it's all fixed and it runs like a dream!

Edited August 25, 2010 by ksx

[ksx]

...and also, thanks for your help guys!

[Trozzle]

Good to hear mate!