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Revs Fluctuates Up And Down At Idol, Also Misfires

Duff_man

By Duff_man,
in General Maintenance

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Duff_man Collaborator

Duff_man

Posted
Posted

hey,

I have a 93 r32 skyline and ever since i have bought the car about a month ago when i am sitting at idol the Revs fluctuate up and down around 100 -300 revs, also misfires occasionally

i have only really noticed this when its just sitting and idol and will get worse if i leave the car to idol for long periods

it does not do this when the engine is cold and the choke is on, it really only happens when the car is warm/hot

i have recently replaced the air flow meter, oxygen sensor and had the TPS (Throttle position sensor) adjusted

If anyone knows of wat could be making my car do this or have any suggestions don't hesitate to Post

cheers

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TiTAN Grand Master

TiTAN

Posted
Posted (edited)

clean out your idle control unit with carby cleaner. it is located on the back of the top half of the intake plenum and should be held on with 3 bolts.

Edited by TiTAN
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Benzino33 Experienced

Benzino33

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is that like the iacv valve?, would the fix the misfire as well?

Yes the Iac valve will fix ur hunting idle..the misfire would be a coil pack issue

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Benzino33 Experienced

Benzino33

Posted
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ok. yeah but if the misfire was a coil pack, it would continue as i rev up the engine wouldnt it?

Yes it does both, my car used to misfire at idle like mofo, and up above 500rpms, after i changed the spark plugs to platinums and changed the coils, it ran beautifully..But if u gonna change the coil packs,have the taped up or covered in silicon gel so no spark escapes from little hair line cracks. Either that or get splitfire coils and u wont regret it

chrrrz

Ben

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Parag0n Mentor

Parag0n

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Are you running an aftermarket ECU? I had idle hunting problems running power FC base maps on numerous RB engines.

Otherwise I would be cleaning out your ICU and changing sparks, check the coils and leads too see how they look as well.

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Duff_man Collaborator

Duff_man

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nah standard ecu. cheers, yeah i'm thinkin it could be the leads to coil packs, i have read other people's posts with similar problems and they were talking about CAS, wat is CAS? and if it is this how can i check

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Benzino33 Experienced

Benzino33

Posted
Posted
Are you running an aftermarket ECU? I had idle hunting problems running power FC base maps on numerous RB engines.

Otherwise I would be cleaning out your ICU and changing sparks, check the coils and leads too see how they look as well.

Yeah,,check the ignition leads and look for a vacuum leak too,,might just be that

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nIsMo86 Experienced

nIsMo86

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CAS = Crank Angle Sensor...Its silver and sits on the front of the motor on the exhaust cam.

ICU is not the name...Its AAC valve = Auxilary Air Control Valve. It is located at the rear of the plenum and looks like an alloy block with a small can on it. Has connector plugged into it.

I'd suggest you clean out your AAC valve first and go from there. Theres a guide on how to do it on here somewhere. Have a search and you will find it.

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  • 3 weeks later...
cattivo_69 Community Regular

cattivo_69

Posted
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CAS = Crank Angle Sensor...Its silver and sits on the front of the motor on the exhaust cam.

ICU is not the name...Its AAC valve = Auxilary Air Control Valve. It is located at the rear of the plenum and looks like an alloy block with a small can on it. Has connector plugged into it.

I'd suggest you clean out your AAC valve first and go from there. Theres a guide on how to do it on here somewhere. Have a search and you will find it.

if u disconnect the plug on the AAC wat will happen to the car while its running? my idle is all over the place, and when i clutch in too quick at the lights it stalls

other problem is the car is running way too rich.. the back bumper is always black??

wat to do?

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PUDZ 32R Enthusiast

PUDZ 32R

Posted
Posted

the AAC valve only controls the engine idle when you turn the air con etc on and the IAC or idle air control valve does the idle if i am not mistaken?

clean them out and check for vac leaks even a tiny hole in your intercooler can screw the AFR and this will make it run heaps rich and idle like a bitch.

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