# R33 GTR rough idle and 'misfire' up to 1500-2000 rpm



## pav2412 (Jan 24, 2021)

Hi all,

I've tries using the search function on the forum and on the the Skyline Owners forum but can't find a solution to my particular problem. I bought the car back in Nov 2020 and have only taken it out possibly 3 times since, so i don't know if this is just how it runs on idle or is i actually have fault, and possibly it has only just become more noticeable. 

Its an RB26 forged engine running a Link G4 so maybe it just idles 'lumpy' because of the way its mapped, i don't honestly know. So far i've checked and changed the plugs, swapped out the Splitfire coils for genuine good Nissan coils, checked the vacuum and boost hoses, i found a pipe sitting loose which i think came of a solenoid that goes to the BOV, this made no difference on attaching it back. I also found a vacuum connector closest to the bulk to be sucking in air, into the injector housing/ lower part of the intake manifold. I capped this connection off, but all it did was drop the revs on idle down to 900-1000.

My engine runs rough on idle, on cold start or even once warm. I can feel a 'misfire' on light acceleration from idle to approx 2000 rpm, after that it seem ok or maybe its just not as obvious in the higher rev range. From what i can tell the car drives fine, no misfire under load, could this be normal for a forged engine?

Any help would be greatly appreciated.

Many thanks


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## TBane (Jun 22, 2021)

I think this is due to the Carburetor Issues and Bad idle Air Control Valve which I too had with my car. You should consult a mechanic to get it right.


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## Johnny R33 (Sep 11, 2020)

You mean TB ( Throttle Body ) not carburetor, since Skylines only have TB's..


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## joshuaho96 (Jul 14, 2016)

Check compression first. Also look at the cams. If the cams are high duration then yes the engine will feel horrible at low RPM, there's no tuning around physics.


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## lee_gtr (Aug 12, 2015)

I would get someone to check the tune, i have tomei poncams and yeah the idle is slightly lumpy which is fine but low rpm cruising is like driving a stock car. Who mapped the car?


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