Skyline Idle Problems

 The Nissan Skyline is legendary, thanks to far too many appearances in video games, movies, and manga.  While the car is certainly way too much fun to be legal, it's not without its problems.  The RB series of engines that powered the most desirable Skylines (we'll say the cutoff point is the RB20DE, anything lower is probably not worth fixing) have a habit of developing idle problems, particularly as they work their way into their upper teenage years.

As the owner of an RB20DET powered R32 GTS-t, this author has experienced and dealt with the afformentioned RB idle problems.  What was supposed to be an easy diagnostic and fix turned into an expensive ordeal.  But hey, that's Skyline ownership for you, right?

Instead of covering the R32, R33 and R34, I'll cover everything that could possibly cause an idle problem across all three generations of the car.  I suppose this guide could also cover the RB20 powered R31 Skylines as well, though I'm not 100% sure about that, as I believe there's only one or two R31 Skylines in all of Canada, and I've never actually seen one in person.

Is it REALLY that hard to hold a steady idle, you stupid engine!? * Throws wrench across the front yard*
Is it REALLY that hard to hold a steady idle, you stupid engine!? * Throws wrench across the front yard*

Pops, misses, and stalls.

There's a good chance that if you ever find yourself owning and driving an RB powered Skyline, you'll also run into the inevitable idle problems.  These typically manifest themselves as pops, misses, or stalls caused by rpm's dropping.  In this author's case, it started as a slight pop every now and then, turned into a very audible "miss", and then manifested itself as stalling when coming to a stop and stepping on the clutch.

Diagnostics and potential fixes

When sitting at idle, the car makes a "pop" noise

A popping noise will typically also show itself as a very slight dip in rpm. The tachometer may show the rpm drop to be somewhere in the vicinity of 50-60rpm. This typically happens after the car has warmed up to operating temperature.

  • Have you inspected your spark plugs lately? Pull them out and take a look. If the gap is too large, the plug may not be able to create a spark, or may create a weak spark. If your car is older and the coil packs are original, you can decrease the spark plug gap down to 0.8mm to help cover a weak or dying coilpack. If you're running higher than stock boost levels, you should gap to 0.8mm anyway. If you have not changed the plugs since buying the car, change them now. New plugs can wake an engine up and make it feel like a brand new engine.
  • How do your coil packs look? You can use a multimeter, but most agree that if your car is 10+ years old and has covered more than 100,000km on the original coilpacks, you should look into replacing them. Coilpacks can developed a hairline crack, which can cause them to ground out. Replace them with OEM coils (the best, but most expensive option), or aftermarket coils, such as those available from Splitfire or other reputible companies. When you replace your coilpacks, you should also replace the coilpack loom, as they harden over the years and become brittle.
  • Check your throttle position sensor (TPS). You can test the sensor with a multimeter. Tie into the middle wire in the group of three wires that are at the bottom of the connector (this is on the R32 gts-t, it may be different on the R33 And R34). The TPS should give you a reading of .48. Honestly, if the TPS looks old, you should replace it as routine maintenance, as they only cost about $40.00. Make sure its adjusted to .48 after you install it.

When coming to a stop, the rpms drop causing the car to stall

Nothing is quite as annoying as having to give the car some go pedal every time you come to a stop, to prevent the engine from stalling.

  • The throttle position sensor (TPS) is responsible for helping your engine maintain a proper idle. There is an idle contact within the TPS that is supposed to touch, making the car go into idle mode. If the contact isn't touching, it is possible that the revs will continue to fall as the engine doesn't "know" that it's supposed to start idling now. A quick way to test the TPS is to give the plug a wiggle. See if the engine RPM's change. If continued wiggling of the plug causes the engine to stall, replace the TPS.
  • Do you have an aftermarket vent-to-atmosphere blow off valve? Skylines are equipped with a MAF (mass airflow sensor), which means the air that gets vented by the blowoff valve has already been metered. When you vent that metered air, it causes the engine to run extremely rich, which causes impressive flames out of the exhaust, and unfortinutely, stalling problems. If your car has the stock ecu and an aftermarket blow off valve, you either need to re-circulate the blow off valve back into the intake, after the MAF, or you need to get a re-tune of the ECU. A very dodgy fix is increasing the idle speed.
  • Clean your MAF.  Don't use brake clean, whatever you do.  There are MAF cleaners available that you can buy at pretty much any auto parts store.  If you have been using an aftermarket airfilter with an oiled filter element, throw it away and kick yourself in the shin.  MAF equipped cars hate oiled air filters, because the oil eventually begins to mess up the little wire in the MAF.  Replace the oiled filter with a dry style filter, and clean your MAF.

These are the fairly common causes for Skyline RB engine idle issues. I'm sure there's plenty of other causes, but I've yet to encounter them in my own travels. If you've had any problems with yours, let me know in the comments and I'll add it to this article. Keep in mind that if you're rolling around in an R32, well, these are old cars now, and old cars tend to be maintenance queens. When you pick up an old sports car, it's pretty important that you replace just about everything you possibly can with your budget. Don't even think about aftermarket mods until after you've replaced any old and tired sensors, cleaned the MAF, replaced the coils/loom/spark plugs, and inspected every other major component. Replacing the old vacuum lines is also a great idea, as you can be sure that there is probably a vacuum leak somewhere. Replace the fuel filter, fuel pump and injector loom as well, if you can afford it. If you can't afford it, save up money until you can! 

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Comments 17 comments

ajaroslav 6 years ago

After installing a RB20 into a 240Z I experience many of the idle issues your described including a full stall during throttle off. It was determined this was caused by irregular air flow through the MAF.

The solution turned out to be moving the MAF to a blow thru position. The result was runs perfectly...even with all emissions removed.

A bit unorthodox but VERY effective.

Thanx for the article!

pat 5 years ago

my car started to clunk and then die i put fuel filter in and i am using a carborator and injections fluid now it it sounds like a zip and also now the car when it idles it pops what is wrong?

Pete 5 years ago

this article is soooo helpful... ive been looking up videos on youtube and everywhere to try figure out why my car keeps stalling on me. thanks a heap. finally some help

Owtaman 5 years ago

I have idling issue on my ECR33-S2, RB25DET, it fluctuate but does not stall.

Recently I replaced no.2 and no.4 ignition coils and I see the biggest improvement since all the other things I have done to fix this idling issue.

Dean 4 years ago

Great write up ive gotta rb20det in a s13 silvia been tryin to fix an idle problem only happens after revving the car say at idle it'll die, i watch my boost guage it reads 20 vaccuum then i rev it and when i back of it reads 30 vaccum??? Then it goes back to 20 but that's only if it doesn't stall frustratin the hell outa me

But from this write up im gonna try find somewere they sell tps's for a decent price n go from there, cheers mate :) 4 years ago

Im having problems with high idle on rb20 got idle turned all the way down and still idles about 1500rpm messed with the TPS still doing the same thing.first the motor would idle high then cycle to low then high.Seeing if you had any ideas.

Thanks Rob

tammie 4 years ago

any chance you could tell me if i can put a r33 tps in a r31 motor

rfucknb 4 years ago

You can also try cleaning the aac valve on the plenum theres a detailed write up on skylines australia.

seems lots of people are happy with the results and they recommend it to all rb owners, i just cleaned mine waiting for it to dry

shanon 4 years ago

i have a idle problem and overfueling, new afm fixed the overfueling and bad idle but now sometimes it still drops down 2 low and stalls . it will idle fine on its own but as soon as you give it a rev it goes up then drops big nearly stalls or sometimes does stall

25tskyline 4 years ago

I recently aquired a skyline with an rb25det, and im having trouble with it when i try to go full throttle/boost when in gear. I can only reach .5 bar before it starts stumbling/stuttering. While in neutral this doesn't happen though. Please help!!


curtoyeh 4 years ago

rb20 in r31 conversion MAP sensor wiring

sham 4 years ago

hi i have a rb25det put a new turbo but i have oil coming out the airflow meter and my car is smoking very bad what could be the problem

Tommy 4 years ago

To Sham.

Since you have a bigger and better turbo, it sucks oil from the breeder. Have a cath tank for oil mounted and no more oil problem. Had the same problem with my built.

Drifting Skyline r34 rb25det neo6, 600hp.

william 4 years ago

hae m8,my r32 idle pulsates between 1ooo nd 2000rpm.ive changed the tps.any ideas on what could be causing this

Jay Kalis profile image

Jay Kalis 19 months ago

So 4 months ago i bought my first skyline also is the first turboed Between 2500 and 3000 it revves up and down by itself from cold to running temp it back fires it stalls every now and then guy I got it from pulled out $12g werth of receipts for the motor full mapping and rebuild it was fine driving her little hard spent the last week driving it grandma and it developed all these issues stalling, reving to 3000 and cutting out and now the weird reving between 2500 and 3000 help me please I miss driving my skyline already

Peter Chan 5 weeks ago

i got a idle problem after my car warm up about 20 minutes and turn on the air-con, the idling suddenly drop down 100-150rpm together with the oil pressure. The oil pressure display is not stable and drop down to O just 1-2 second then back to normal,

it seem that these appear every-time when the air-con start to refrigerating, can anyone give a hand

anthony 4 weeks ago

we have a a vaccum hose 1\4 inch running from inlet manifold to a little black box ith grey electrical connector , what is this little blck box ?

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