Idle Issues

[skybox 32]

Hi guys!

I have a crappy idle issue with my r32 gts-t and have done a bit of investigating on the forums.

1. I have cleaned and replaced the acc controller.

2. I have eliminated the possibility of TPS. (Changed that over)

3. Changed the Crank Angle

I still cant seem to work out why the idle is so rough on start up... and rises when engine is warm to around 1100 rpm when decelerating at the lights

I havent changed the plugs yet i will do that shortly.

Is there anything else that could be making this idle hunt / want to stall so much?

I have moved the TPS a little higher to compensate the low idle and adjusted the aac.

I know that there is an issue with skylines regarding this as i have read the forums.. Just wondering if there is any other suggestions.

Does anyone know a decent / cheap electronics place to get the diagnostics checked out. im a bit hesitant of going to Nissan just yet as i dont have a diagnostics tool.

[blind_elk]

Have you adjusted the TPS correctly. If it is "off", it won't send a "throttle closed" signal to the ECU, and the engine will idle fast.

Have you adjusted the AAC correctly?

Have you had the injectors cleaned?

Don't understand about the diagnostics test. Nissan are the ones who will have the diagnostics tool - you don't need one. I might be able to recommend someone, but they might not be in the same area as you.

[skybox 32]

Have you adjusted the TPS correctly. If it is "off", it won't send a "throttle closed" signal to the ECU, and the engine will idle fast.

Have you adjusted the AAC correctly?

Have you had the injectors cleaned?

Don't understand about the diagnostics test. Nissan are the ones who will have the diagnostics tool - you don't need one. I might be able to recommend someone, but they might not be in the same area as you.

Hi!

Thanks for the swift reply.

As far as the diagnostics tool goes, what i meant was that I didnt have a diagnostics tool but didnt want to go to Nissan who would prob charge an arm and a leg to do a diagnosis. Id rather try eliminate every possibility before chekin diagnostics.. ;-)

As for the TPS and AAC I have only adjusted roughly by idle level as I dont have access to a R32 Manual. I purchased the r32 Specs on CD off ebay so that should be coming soon. Is there a more accurate way of adjusting the TPS and AAC?

I am living in the Ringwood area by the way.

Cheers

[LatinR33]

Hey wcastrey,

Had the same prob as you some person increased my tps when I had a BOV installed and tps was in closed throttle mode and car was running bad. Went to a mechanic with a consult and he adjusted the tps accordingly and no more idle probs. I suggest you find a mechanic who has a consult so they can fix up the tps position. hope everything work out.

[Jmaac]

Got the right plugs in?

[SKYPER]

I have the same problem on my car and it's the IACV valve (cold idle valve)

that needs cleaning because it's sticking.

A way to avoid the stall is applying a little bit of throttle when starting

the engine or crank the engine for a longer period.

I noticed IACV valve replaces the choke on the dash of older 80's style Nissan's

and is known as a automatic choke, that I think is controlled by ECU.

The valve inside the IACV valve can stick due to being dirty or can't be repaired

thus needs to be replaced.

The IACV valve on the RB20DET is located on the bottom half of intake plenum,

just behind the throttlebody. If you follow the rubber hose from AAC valve to

J pipe that goes over the top of motor, you'll find a T section and the single

hose from that T section leads to IACV valve.

What you need to do is remove the IACV valve and spray down where the single

hose connects to IACV valve and remove / clean out the built up dirt. Then check

the movement of the valve inside the IACV valve with a flat head screw driver. If

still sticky, then replace the IACV valve.

Before refitting IACV valve, adjust the screw on IACV valve so the valve is fully

open. Can't remember which direction it was.

Basically how it works is IACV valve is fully open when engine is cold and

slowly closes when the engine warms up. Once the engine is warm, ACC valve

takes over to supply air to intake plenum. I think IACV valve adds extra air to

intake plenum which combats the rich mixture in the cylinders when engine

is warming up.

Sometimes one or both of these valves can cause problems and need replacing.

Other area's to look at with similar symptoms can be air leaks in intake piping,

faulty or misadjust TPS and o2 sensor failure.

I hope the above helps.

Edited January 30, 2008 by SKYPER

[skybox 32]

I have the same problem on my car and it's the IACV valve (cold idle valve)

that needs cleaning because it's sticking.

A way to avoid the stall is applying a little bit of throttle when starting

the engine or crank the engine for a longer period.

I noticed IACV valve replaces the choke on the dash of older 80's style Nissan's

and is known as a automatic choke, that I think is controlled by ECU.

The valve inside the IACV valve can stick due to being dirty or can't be repaired

thus needs to be replaced.

The IACV valve on the RB20DET is located on the bottom half of intake plenum,

just behind the throttlebody. If you follow the rubber hose from AAC valve to

J pipe that goes over the top of motor, you'll find a T section and the single

hose from that T section leads to IACV valve.

What you need to do is remove the IACV valve and spray down where the single

hose connects to IACV valve and remove / clean out the built up dirt. Then check

the movement of the valve inside the IACV valve with a flat head screw driver. If

still sticky, then replace the IACV valve.

Before refitting IACV valve, adjust the screw on IACV valve so the valve is fully

open. Can't remember which direction it was.

Basically how it works is IACV valve is fully open when engine is cold and

slowly closes when the engine warms up. Once the engine is warm, ACC valve

takes over to supply air to intake plenum. I think IACV valve adds extra air to

intake plenum which combats the rich mixture in the cylinders when engine

is warming up.

Sometimes one or both of these valves can cause problems and need replacing.

Other area's to look at with similar symptoms can be air leaks in intake piping,

faulty or misadjust TPS and o2 sensor failure.

I hope the above helps.

THanks for your insight skyper.. me an a mate ( mechanic) last night blocked off the IACV valve and the related hose to see if that would help when we cranked it over. Still was hunting bad upon start up, so we changed it back. He mentioned that Ill try clean out the valve and let you know...

Also found when driving home from work today that it is starting to run a little lean. There was a burble on idle and when i drove the burble would go away. Now it seems after accelerating a little and taking my foot off the accelerator i can hear the burble.. Could this be another issue? or related? Maybe an air leak somewhere?

And yes, i have the right plugs in

[skybox 32]

oh and i dont think its the 02 sensor as we had a spare lying around and changed that over with no response.

[skybox 32]

oh and i dont think its an 02 issue, as we had an 02 sensor lying about and changed that over with no response

[SKYPER]

You're welcome.

Engine probably would have idle problems when warming up, as blocking off hose to IACV valve is not

allowing the extra air into intake plenum.

Reading the thread and your post again, I think the sticky IACV valve could be part of the cold start

up problem, but it seems you have replaced the AAC valve without resetting base idle on stock ECU

and TPS could be incorrectly adjusted to the engines problems instead of the recommended factory

voltage settings. So after you have fixed the problems, you'll probably need to readjust TPS to factory

voltage settings.

Also if base idle setting on ECU is set at 750rpm and screw on ACC valve is set at say 1100rpm,

revs can bounce between those rpm's. Basically ECU adjusts idle to 750rpm and idle valve raises

idle to 1100rpm. I guess it would explain why engine rpm drops to 1100rpm when deaccelerating.

You can reset base idle on stock ECU with Nissan's Consult.

Or another alternative is Datascan software, cable, which

allows you to adjust the base idle, reset ECU, erase sensor

error codes, etc.

Datascan software, cable, etc -

http://www.blazt.biz/?gclid=CMCD7rquoJECFRscawodbmIHOg

Screen shot of software, "Base Idle Adjustment" feature -

http://www.blazt.biz/products/images/datascanactivetest.JPG

Burble or pop sound could be flames out the exhaust due to engine running

rich. This could be from ECU running in kind of what you could could call a

limp mode. I think ECU switches to the alternative low octane retarded

ignition map, rich fuel map.

Edited January 31, 2008 by SKYPER

[kcmagee]

What about your Ignition Coils. My car started running much the same especially when it warmed up say 2-5 mins into driving, turned out coils 1 and 2 were below spec level... so i bought splitfires....

[SkyGts4]

Its probably an air leak somewhere in the engine bay or in the exhaust. Have you had a new exhaust installed? Aparently there's mechanic automative type stethacope that you can buy at any automotive shop that can help with detecting air leaks...Hope that helps...

[skybox 32]

Its probably an air leak somewhere in the engine bay or in the exhaust. Have you had a new exhaust installed? Aparently there's mechanic automative type stethacope that you can buy at any automotive shop that can help with detecting air leaks...Hope that helps...

thanks for all the responses.. im goin to get a mate to do a ecu diag so as to track down the culprit.. atm it could be a range of things. so ill keep you guys posted when i get the results

[skybox 32]

thanks for the replies guys.

Just wanted to let you know

i sourced the problem of my idle issues to the Air regulator. Things i did which also may have affected idle where:

Changed fuel filter - this was a bitch to change haha

Replaced spark plugs to iridiums 0.8mm spacing - original sparks werent fouled

Checked coil packs - no hairline cracks fortunately.

Also did an oil change.

Wala.. I swapped the air regulator as the DIY said to undo the four screws to clean the insides.. but they were so tight i didnt bother, and i just swapped it for an air regulator off my old engine..

Now i just have to set idle correctly again and ill be all set..

cheers

[Jmaac]

any mods?