Changed my front brake pads yesterday and now my Z idle is very high. I did clean around the bottom if the engine and remember hitting the wire in the picture below.It had tape wrapped around it so removed it and there is one yellow wire. What is this for?

 

That looks like the oil pressure sender.

Do you have a Conzult Gary?

Do you have a Conzult Gary?

 

No mate I dont.

That looks like the oil pressure sender.

 

Thanks Stephen and that would not affect the idle.

Ok firstly, get a Conzult! It can make diagnosing these things easier. For example in this instance you could electrically disconnect the AAC from the IACV without physically disconnecting it, which’s saves time and potential damage to the harness (especially if it’s original!).

 

Disconnecting the AAC and monitoring its position could help isolate a vacuum issue from an AAC fault. Have you ever removed the IACV to clean inside it as it’s possible that it’s gunked up causing the piston to stick.

 

Have you had any hoses or vacuum lines off recently and do you have a boost leak tester?

Thanks Stephen and that would not affect the idle.

 

Yeah your right, that wouldn’t impact it. The brake work is probably coincidental. There’s a multitude of factors involved in the idle control, as Joel said you could do with hooking it up to consult or similar. When you say high? How high?

For reference, this is the AAC connnector to remove. You need to remove the retaining clip with a pick (and a magnet so you don’t drop/lose it!) and then you can gently pull it off. Once removed, your idle should drop down to its base setting of around 650/750RPM.

 

Idle is at 1500 and if its not an obvious fault and an easy fix then I might need to get my mechanic to check it over. Will look into what you posted up JP.

Given it's sat around 1500 Gary, it's probably the hard idle switch mate. Try unplugging it and putting it back in

Given it's sat around 1500 Gary, it's probably the hard idle switch mate. Try unplugging it and putting it back in

 

Where is it Lee?

Assuming your engine is warm, here are the FSM steps:

 

ec-69.pdf

If you do decide to remove the IACV for cleaning/inspection, that pic clearly shows the location of the 4x10mm bolts holding it on. I’d recommend removing the small scuttle trim and the battery for easier access.

 

You’ll need a new gasket for when you refit PN 2378540F00

 

 

 

https://www.allcarpartsfast.co.uk/nissan/nissan-2378540f00-gskt-aac-valve/

Where is it Lee?

 

Just off the tps. I think its a grey oval connector off the top of my head

This is from Z32 wikispaces:

 

Consult Interface

The best way to set the TPS is to use a Consult interface such as Nissan DataScan or conzult. This allows you to quickly and easily see both the voltage of the Throttle Sensor and condition (ON or OFF) of the Hard Idle Switch.

After loosening the two small screws holding the TPS to the driver's side throttle body, rotating it will change the states of the two sensors. Rotating it clockwise lowers the Throttle Sensor's voltage, and rotating it counter-clockwise increases it.

There is a "sweet spot" found while rotating the TPS where the Hard Idle Switch will turn on WHILE the Throttle Sensor reads between .4v and .5v. A common method of failure for the TPS appears where these two requirements cannot be met at the same time. That is, it can be set to show voltage between .4v and .5v, but the Hard Idle Switch shows off. If it's set to a position where the Hard Idle Switch turns on, the Throttle Sensor won't be in the proper voltage range (often around .3v). Owners will often set their TPSs to in the ~.4v-.5v range, but without the Hard Idle Switch being on, the car will idle high (between 1500RPM and 2000RPM).

 

If you're unable to get the TPS voltage and hard idle switch to their "sweet spot," try this:

•Rotate the TPS so that the TPS voltage is reading between 0.4 to 0.5v.

•Unplug the gray oval TPS connector for several seconds. You should be able to see the voltage (as displayed via consult) rise. After about ~8 seconds, the hard idle switch should display "on"

•Reconnect the gray oval TPS connector.

 

Another, less common method of failure is one where the Throttle Sensor "track" becomes dirty. This causes the voltage to have "dead spots", which can present itself as hesitation or bucking while driving.

Sorry, here's the link. I recon it's probably the hard idle switch being off, rather than on when you are idling. Fairly common occurrence IMO:

https://z32.wikispaces.com/Throttle+Position+Sensor

Careful pinching that air regulator pipe as it’ll likely split! Removing the hose and blanking it might be the best option. Out of curiosity, when you start from cold and it revs up, does it ever drop down or does it just stay at 1500 when hot?

Thanks for all the posts guys I am very busy today with a BBQ for 12 people but I have fiddled with a few wires and taken it for a drive and it now idles at 1000 revs but new issue in that the boost gauge needle is flickering about on idle and mostly sits at -7 on idle. Should it not sit at 0 in the center? Car drives and boosts well.

It shouldn’t sit at 0 on idle, -7x100mmHg is good.

It shouldn’t sit at 0 on idle, -7x100mmHg is good.

 

Ah thats good then just a worry why sometimes it flickers back and forward across the gauge.

So what was it then

So what was it then

 

Haven't a clue mate I checked all the wires and connections and took it for a drive and the idle dropped.

 

Drove it to work this morning and all is good so still don't know what caused the high idle and boost gauge needle flickering back and forward on idle. Nervous now that it will do it again so might get it checked by an expert some day soon. MOT on Wednesday wish me luck. :)