Idle hiccup

[krystalized_jdm]

Going to be upgrading coilpacks, I was so annoyed by the powerloss last season and how I couldn't hit full boost without hesitation.

Currently organizing a splitfire coilpack group buy if I find enough people, and a vendor price I like.

[ToroGTS]

this is insanely typical of an ignition problem, either weak coil or weak ignitor. The 'hesitation' you are talking about when hitting boost is the increased cylinder pressure literally blowing out your spark like a candle. The idle is likely the IACV and as people said can be adjusted. with the engine idling full warm use a long Philips head screw driver to adjust the idle down (clockwise to lower), you should be able to get idle to 800 rpm or below. If you are still at 1000+ territory after this I would suspect a vacuum leak and if the idle is bouncing around on you possibly a TPS sensor idle contact issue. After this pull your negative battery cable off for awhile to reset the computer and then start it up again and let it idle for a little, take it out for a spin.

[krystalized_jdm]

Idle doesn't bounce around, it'll start up at around 1200 then go to 1800-2k right after. It never fluctuates after that.

I will adjust the IACV today and see what I get, for the mean time I know I have vacuum leaks as I am still waiting on the t bolt clamps for my front mount. (Idle was the same, previous to the front mount)

I am currently looking to replace my coilpacks, so hopefully issue will be fixed by this season.

[krystalized_jdm]

Took a look at the Iacv today, unable to find a "big Philips screw" on the iAcv.
To clarify I was looking at a device on the side closest to the firewall on the intake plenenum. Only thing I seem was a flat and the mounting screws.


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[Frankyy]

I mixed up the rb26 iacv I thought they were the same for a second, there is 4 mounting bolts for the iacv there should be another screw wether it's flat or Philips there is only 1 other screw on there to adjust it

[krystalized_jdm]

Alright, I figured the flathead was the one to adjust. I'm not in a rush so I figured I'd wait before tampering with the wrong thing.

Thanks frankyy

[Frankyy]

Abd the iacv is always adjusted when the engine is cold, the iacv let's more air in when the car is colds and closes once it warms up a little bit.

The reason why a car with a blocked off iacv doesn't idle well on cold start you need to be on the gas for the first minute or so, your foot on the gas is acting as the iacv technically, and hopefully better coilpack will also help the hesitation

[krystalized_jdm]

Should I not bother with it after it is warmed up? I tried adjusting when cold nd seen no difference. It warmed up, I gave it a little rev now it won't stop dying haha


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[krystalized_jdm]

Well whatever I did, royal ****** it. I adjust screw all the way out, and all the way in and tried in the middle. Car starts, and dies immedietly. If I push on gas, it runs like s**t to the point my door/glass was shaking while it was open. When I push gas as well to about 2k, I am running at 0 vacuum and you can hear turbo spooling (if that is of any help) but it seems extremely low rpm for my turbo to be starting to spool to 0 vacuum.

Tried running with iacv unplugged and engine died as well.

To edit my above post, car was not warmed up. Car was running for 5 minutes, and temp guage was still low so I was editing the IACV on a cold engine.

When I adjusted it the first time, I put the IACV screw all the way in. Made 0 difference on the car and how it was running, I gave it a little rev in the car to about 35-4k and right as it was reving down it died. Won't stay running since that

I reset the ECU after I adjusted it

I am going to go scan for error codes and check the IACV voltage w/ consult reader.

[krystalized_jdm]

Update from last post

I checked for error codes, got nothing.

The engine seems to be really really "chuggy" and when I say that I mean it sounds like it has killer cams. It is retarded, I think adjusting the IACV made it throw a s**tload of fuel at it and it is causing that.

This issue I am having here was the exact same issue I had with it in 2010 (sadly, I don't know what fixed it as I had a shop take care of it

Edit - Read somewhere it is best to unplug it, adjust it and then plug back in.

I'll go try that hopefully come back with good results.

[krystalized_jdm]

Update from last post

Sorry for being a post whore, but I am worried about this as I have next to no knowledge on the matter.

Unplugged the iacv, adjusted it outwards (assuming that gives it more air) and engine RAN on its own but was still a bit chuggy (not excessively like above post) and wanted to die. It was pushing out some VERY black exhaust, and after about a minute it went to a greyish white so above post was correct on it giving to much gas.

Now it is idling at about 800-900 but doesn't stay at a constant value and seems to want to die. I moved the IACV out to the furthest the screw could go (without removing it obv) and I still have same results.

Any input is appreciated.

[Skym]

Ok.

Check that you have earth under ignition module mounting screw. It can blow ignition fuse if don't have that earth connected.

Which idle valve are you adjusting???

AACV (Auxiliary Air Control Valve) is located on back of intake plenum facing firewall.

IACV (Idle Air Control Valve) is located on top of bottom half of intake plenum.

IACV is only used during warmup. Once engine is warm, IACV is not used anymore as it's fully closed.

If adjusting AACV the manual way, turn diagnostic screw on side of engine ECU all the way to left to put ECU into idle rpm adjustment mode (note current position and amount of turns on a piece of paper before adjusting screw) unplug AACV and adjust idle rpm to 650rpm (as shown on white sticker on passenger side, under hood) and plug AACV back in. If idle stays the same, return screw on side of ECU to where it was before adjusting it. But be aware, adjusting screw on side of ECU to the right can raise idle rpm slightly (I think 250rpm at a time). It's easier if have Consult (go to Nissan dealership or use Nistune tuning software), as saves turning screw on side of ECU (can put ECU into idle adjustment mode via Consult).

With coilpacks, remove and check them on bench with a multimeter (if don't know how to, save up and get a mobile auto electrician to check them) to check if they are ok. Then pull sparkplugs and check for black tip (coilpack not firing properly). Ignition module can be checked by swapping it over with a known good ignition module, or auto electrician can check on a oscillioscope.

If engine is trying to wander with idle rpm, unplug o2 sensor. That should make engine idle smooth and rpm is steady. Faulty o2 sensor, misadjusted TPS or faulty TPS (that + lazy 02 sensor could explain the stalling), idle set too high via AACV, a few failed coilpacks could be the problems with your engine. The o2 sensor is checked, changed if necessary every 40-60,000km, but not many replace o2 sensor (same with TPS).

If this is too much for you to do, take it to a Nissan Dealership that deals with Skylines and pay them to reset, fix everything.

[krystalized_jdm]

I don't know which one it is now that you mention it, I adjusted the one that is closest to the firewall. So I guess that would have been the AACV.

I will take a picture of what I was using yesterday, but now I am quite sure it is the AACV.

I will also attempt to do what you recommend in the morning skym.

The coilpacks should be fine, the engine was running smoothly (with the exception of the hiccup)

[Frankyy]

You also said you had a boost leak, and you were waiting on some clamps, even if the piping is in properly with no clamps it can still leak some air out, when my piping blew underneath my car, it took about 1-2 minutes and destroyed the plugs, so look at those they are probably due for a change, get cheap ones as you are still trying to solve this issue and might happen again

[92GTSTproject]

lol dont turn the screw to the extremes, all it takes is little adjustments, if you screw it all the way in it wont hardly start at all let alone run put it back in the middle and turn it accordingly in SMALL increments till you get the idle you want