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Lumpy Idle

Primordial

By Primordial,
in Engines & Forced Induction

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Primordial Grand Master

Primordial

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My car has a very lumpy idle. At 700-900rpm the rocks around and the idle just feels lumpy.

Someone pointed to the fact that this may be a symptom of aftermarket cams.

Does anyone know of a way to check to see if my RB25 has got aftermarket cams? The car came with lots of other goodies on it, so I wouldn't be too surprised if they were non standard items.

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Primordial Grand Master

Primordial

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Nah I havent checked this, but i do notice that at idle my car seems to burn a lot of fuel (black smoke out the exhaust).

I was poking around the engine bay this morning, and didnt notice anything out of place or loose - including the hoses/pipes...

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kyle785 Collaborator

kyle785

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abit more info might help as in how long you had the car and how long have you had this lump idle but as you asked in your post a good way to find out is to remove your cam covers and have a look jsut a few ideas

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Primordial Grand Master

Primordial

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I've had the car just over a year, and its been lumpy since I bought it. I've had the PFC tuned a couple of times so if there was something wrong (ie. vacuum leak) i think they guys would have picked it up..

It came with:

Apexi Turbo

Injectors

PowerFC

Fuel Pump

etc etc..

I suspect that its got cams due to the chunky mid-range. If I have a look at the cams, is there any way to tell if they are std or aftermarket?

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Mr. Oizo Grand Master

Mr. Oizo

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I suspect that its got cams due to the chunky mid-range. If I have a look at the cams, is there any way to tell if they are std or aftermarket?

They should have markings on them

I know HKS ones have a HKS logo and the duration on them, so I'm assuming Tomei and whatever other brands make cams would have it too

I'm not sure about regrinds though

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T04GTR Grand Master

T04GTR

Posted
Posted
My car has a very lumpy idle. At 700-900rpm the rocks around and the idle just feels lumpy.

Someone pointed to the fact that this may be a symptom of aftermarket cams.

Does anyone know of a way to check to see if my RB25 has got aftermarket cams? The car came with lots of other goodies on it, so I wouldn't be too surprised if they were non standard items.

VCT solinoid

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MR331307 Experienced

MR331307

Posted
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Mate 1st 3 things ill check are

1) AFR`s on Idle (but seeing your saying its rich removes this but still check they should be around 14.4)

2) Vacuum leak (do you have a boost guage it should read 19 hg)

3) idle air control valve (check if this is leaking not working correctly)

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amosite Proficient

amosite

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If it has HKS Cams you will see HKS Cast into the cams by removing the oil cap and spinning it over a few times.

Unfortunately the duration is on the end where the cam gears bolt to and cant be seen easily. Only early HKS cams have them just under the HKS logo.

The tomei cams are stamped with serial numbers on the cam thrust washers. You might have to remove the rocker cover to see this one.

A couple of things to note.

Most GTST's have a baby smooth idle.

A 4'' exhaust will exhibit a bit of a lumpy idle but is more of a burble from the exhaust then engine idle

If cam timing is way out it can give the same symptoms

Probably the easiest guestimation is if your car has unusually strong mid/top end for the mods.

I imported a car a while back and it had stupid mid range even though it was on low boost at the time. I.e wheelspin in 1st and 2nd on 7 psi! Didnt think anything of it. I cleaned the TB and intake with upper engine cleaner a while later and it was running rough. I didnt remember what it originally ran like as I only drove it once and was away for 6 weeks OS so wasnt sure. Got my brother to look at it and he said it had cams, but sounds like the plugs are f&&*ed! Inspected through the oil cap and he said it had tomei markings on it- but there was no mention on the auction. I emailed a copy of the auction sheet and he said "it has tomei cams" but I couldnt translate/understand that part.

Which brings me to my last point. Once I put new plugs in it, ran a lot cleaner and smoother. Iriway and iritop plugs are great!

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