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Rough Idle When Ac Is Off

DNR33

By DNR33,
in Engines & Forced Induction

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DNR33 Enthusiast

DNR33

Posted
Posted

I recently got a set of 500cc injectors, adjustable cam gear, and new spark plugs fitted to my S2 R33 GTST. Since they all went in my car is idoling really rough when it is at idol, But when i turn on the AC the car seems to idol perfectly. This only occurs when the engine has reached its normal running temp. On cold nights and initial start up it idols fine with the AC on or off.

Could this be due to a lazy tune or parts not fitted properly

Why would the AC make the car idol better.

If any one can help it would be great so i have some information before i go back and ask the shop.

Thanks Guys

DAN

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https://www.sau.com.au/forums/topic/151777-rough-idle-when-ac-is-off/
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46n2 Mentor

46n2

Posted
Posted

i'm not sure if RB's have one but CA18's have a seperate solenoid which controls idle when the A/C is on. If there was a problem with this it might explain why there's only a problem when the A/C is on. Hope that helps...

DNR33 Enthusiast

DNR33

Posted
  • Author
Posted

Thanks for the info guys.

I do have a power FC.

I just wanted to get some ideas so that when i go back to my tuner I have some input incase he turns around and says its normal or something like that. Ill get him to check al the things mentioned.

Thanks Again

DAN

  • 1 month later...
grippy Collaborator

grippy

Posted
Posted

Sounds like you have FC disease! Try moving your AFM further away from the turbo inlet. You have upset the delicate nissan design/tune by running more boost, fuel etc.

Air is bouncing from the turbo inlet causing a pulse effect to the AFM and the ECU cannot compensate quickly of finely enough at idle.

When your A/C comes on the idle is increased enough that airflow is more stable across the AFM.

This is very common with mildly upgraded RB's.

Will always idle a little rough with 500cc injectors but can be minimised to be very slight.

Clean your aac valve and idle screw also, this may help. Cycle your idle screw full range of adjustment when cleaning also.

Rgds, Grippy

Devils_Advocate21 Mentor

Devils_Advocate21

Posted
Posted

Interesting topic which i have to follow, changing injectors this w/e as the tuner reconed injectors. then may have to check that afm thingy, as my does the same, and yes i have thouroghly cleaned the aac as well, noticed with mine the timing jumps with this aswell, and once either fan or ac is on it sits normal aswell, Injectors on this case are deatchwerks 550 cc, On another note could it be battery power?

180or200 Proficient

180or200

Posted
Posted

mine also burbles a little at idle, wouldnt say its a miss, and is smoother when the a/c is on! I have nismo 740's and they are trying to run at less than 1% at 900 rpm, i think its a load issue, and that my light frisby flywheel doesnt help!

grippy Collaborator

grippy

Posted
Posted
Interesting topic which i have to follow, changing injectors this w/e as the tuner reconed injectors. then may have to check that afm thingy, as my does the same, and yes i have thouroghly cleaned the aac as well, noticed with mine the timing jumps with this aswell, and once either fan or ac is on it sits normal aswell, Injectors on this case are deatchwerks 550 cc, On another note could it be battery power?

No it cannot be battery power. You car will run with the battery removed. Start it up and try it out, pull the battery leads off and she keeps humming.

Grippy.

grippy Collaborator

grippy

Posted
Posted

Doubt very much it would be the cam gear. Do any of you guys run after market blow off valves??

I had the same issue with my RB20 after upgrades. The big problem for me was the standard blow off valve was no longer venting back into the inlet pipe just before the turbo inlet. This was because I had a custom inlet pipe made. I had to remove the inlet pipe, have it modified so it could take a pipe from the blow off valve. It now still idles a little rough but only very slight. Before it was stalling and very rough.

The position of the AFM is also very critical to stop inlet pulse. I had to move mine further away also.

Grippy

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