Strange Problem

[Januss]

Hey guys,

Theres this weird thing that happens to my car at stops/when its idling... it does burst of small revs like 250rpms .. kinda like a cough (the car shakes abit). It happens approx. once every 10 seconds. Should i be worried? or is this normal? thanks

[No Crust Racing]

Worried no, do something about it yes.

Could be the AAC Valve (very common cause of idle issues) clean it and see.

Could be the AFM, clean it and see.

Once those are clean you can try resetting your ECU, which is a good thing to do from time to time anyway.

Could be a small vacuum leak somewhere, worry about the first two in that order before this.

Are there any other issues along the rev range?

You don't have the aircon on when this happens do you?

See how you go and let us know.

Cheers

[DrewII]

this started happening to my car not long ago

and now i have a huge problem the car is misfiring. coil packs have just recently been changed too. perhaps my spark plugs are worn i will buy a new set this weekend and test this out. i will also put the old coil packs in one at a time to see if one of the new coils are gone. they are obviously still under warranty but who knows. in the meantime my car is running like complete shit. slow, shaking, sounds like a wrx too.

[No Crust Racing]

Drew do some searching around, also try not to hijack this thread lol, but your issue could be one of the ones on my list. Could also be a crank angle sensor.

Test the stuff on the list and see how you go.

Let us know...

[DrewII]

Drew do some searching around, also try not to hijack this thread lol, but your issue could be one of the ones on my list. Could also be a crank angle sensor.

Test the stuff on the list and see how you go.

Let us know...

hijack? lol. im telling the guy im experiencing the same problem whats the point in starting a new thread.

in response

iv done a full engine diagnostic test with a laptop. cylinders are fine. for some reason the car is running very lean. i richened the AFR ratios and the missing seems to stop. i also did a fuel pump road test however none of these problems brought back any answers.

next i will put some cheap spark plugs in. if this doesnt fix it (one of the spark plugs could be worn) i will replace each new coil pack with my old coil packs to see if one of my new coils are stuffed.

it is "not" the aac valve this is clean. the AFM is brand new. i also put in another ECU and the same problem occured so its not computer related. it "may" be an air leak somewhere in a gasket. this is where i will look next after the coils and spark plugs.

[No Crust Racing]

Hmm, yours is a more curious issue then, most rough idle probs can be solved with the above list but your leaning out implies there's an air leak somewhere. A bad plug would end up with a rich reading as it wouldn't be burning off all the fuel I'd of thought.

Keep us posted mate.

[DrewII]

it is a very strange one

a guy posted a thread with a R32 GTR about a similar issue. his was an electrical issue. still plenty of possibilities.

[DrewII]

well i seem to have two problems

AAV valve broken. turning idle set screw completely in and out changed nothing. and unplugging connectors doesnt change anything either so its either blown or faulty.

i will clean it out tomorrow to see if it revs a little cleaner

my bov is also leaking somehow. i blocked it off completely and the idle problem stopped.

need to buy a new plumb back or second hand stock one.

problem wasnt spark plugs or coil packs.

Edited December 27, 2008 by DrewII

[No Crust Racing]

Hmm no good but at least you're on the trail, keep us posted.

[Januss]

Tested the problem with air conditioning on/off, i dont think it effects the frequency of the "burst of revs". Only seems to happen on idle.

My R33 is an NA (think this should cancel any issues relating to turbos). Ermm, got the spark plugs changed not too long ago, should not be the problm. Havent quite got arround to cleaning the AAC valve yet tho. Anyway, GL DrewII u seem to have a real problem there.

[No Crust Racing]

Give us an update once you've cleaned the AAC and done an ECU reset.

[DrewII]

i have cleaned my AAC valve out

it was very filthy. the DIY AAC Valve guide in the DIY section was extremely easy to do.

the car is still sounding like a WRX so i can't tell completely what cleaning the valve has done. would have done more good than bad.

however im getting a brand new GFB Plumback bov installed so i will let you guys know an update after the new valve has been put on.

my problem is 90% bov 10% AAC valve so i should be sweet after the new bov is put on. fingers crossed.

[No Crust Racing]

Is it running on 5 or something? The WRX sound part makes me think it's not firing all 6?

Keen to see this one resolved.

Keep us posted

[bumble_bee]

its a normal skyline thing..u'll get use to it...

ive also got atmo greddy adjustable bov..and a atmo bov WOULD cause bad idle...

mine is set-up to hard setting..to prevent roughish idle...

the last thing u can do is take off ur idle air control valve..

spray it down wit carby/throttle-body cleaner..wipe off all the carbon..

and put it back on..

also adjust the screw on the side..will adjust ur idle..either up or down...so yeah...

just letting u no

[Corsta]

its been happening to me also, my car after warmed up ussually idles at approx. 600 - 800rpm, then after sitting there for about 5 - 10mins, drops to 450 - 500rpms for a few seconds at that time the car shakes abit aswell.... HELP??

Hey guys,

Theres this weird thing that happens to my car at stops/when its idling... it does burst of small revs like 250rpms .. kinda like a cough (the car shakes abit). It happens approx. once every 10 seconds. Should i be worried? or is this normal? thanks