R34 Gtr Won't Idle

[Chris-06R]

Hi people, hoping I could get some advice from the gurus -

Over the weekend I installed a brand new Trust oil cooler and relocation kit. This of course meant that I did an oil change and put a new filter on, as well as having to pull half the front end off the car...

Anyway, it all went relatively smoothly and when all the lines were installed and tightened and i'd put a fresh batch of oil in I decided I'd run the car for a bit to check for leaks or any problems.

Car started fine, oil pressure came up to normal and the car was sitting happily idleing for probably close to 5 mins. I noticed the oil and water temp hadn't even recorded a value yet (too cold still) so I revved the car up to about 3000 rpm and then back to idle - when it promptly died....

I started it up again and from that point on, it would not idle at all...

So what's the problem?

I'm thinking I could have bumped a wire or something while installing the new lines etc but i'm sure I haven't disconnected anything and forgotten it so I'm really not sure where to start... I was working at the front of the car on the drivers side so I guess there's a lot it could be... AAC valve? CAS? anything else? What could I have possibly bumped on that side? Any other ideas? It could also be related to the fact that it must have just come off the cold start etc as I blipped the throttle and maybe the valve closed... I dunno. I'll have to check if it will idle when cold once it has cooled out.

Any help is much appreciated...

[mr 32]

hey chris

check for vac leaks around the aac or that the aac wiring isnt damaged,it's the best place to start from what you where doing

let me know if you need a hand with it

[Michael's R33]

I had this problem on my GTST not long ago it turned out to be fuel pump resistor near the ariel.

hope that helps. good luck with it.

[paulr33]

if the aac valve was toast or not connected it would have sucky idle with aircon etc on, but it shouldnt stall in normal idle

if cas was toast or not connected the car wouldnt start in the first place

check afm

check tps

look for basic loose connections etc

[Chris-06R]

Cheers for the replies guys - checked all the obvious things but nothing seems out of place. All the sensors appear to be working fine according to the power fc.

It isn't related to temperature at all - won't idle when cold either.

Not sure what could have suddenly changed when I revved it - blow a hose of the AAC valve or similar? Can the AAC valve be completely closed? Seems like the engine gets no air unless i crack the throttle...

[Bsa]

Did you bump the tps out of position that would cause bad idol

[mr 32]

check your intercooler pipes

[DVS JEZ]

Is there fuel in the tank? Check all fuses and cooler pipes

[jjman]

i had identical sypmtoms to this when i did the thermostat housing on the weekend and disconnected/reconnected alot of the connections in that area.

What it ended up being was these 2 connections arrowed in the pic.

-i had only hand tightened them and then when the temp got up the connection went bad n the car kept conking.

Not sure where these are on a GTR but might be worth checking to see if they have come loose or there is a connection for them damaged.

Good luck

[femno]

What happens while youre running it cracking the throttle??

Black smoke? No smoke? Running rough?

Is the engine light on?

go etc > Sensor Check on the pfc and look for anything that may be highlighted.

[Chris-06R]

thanks for all the help,

If I have the throttle slightly open (like 2% on the mfd) car seems to idle happily, maybe a little rich but its hard to tell... The pfc shows all the sensors as normal and working

I'm fairly sure it will be a vacuum leak somewhere but I'm going to have to pump some air into the system to find it - didn't pull any thing off during the filter relocation kit install so unless I've knocked something off accidentally...?

[DVS JEZ]

There are alot of vacuum lines under the plenum above the oil filter. Check all these out. Very common for people to knock em off even when just changing oil filter

[Chris-06R]

Again, appreciate all the help, but I still can't find this problem

Have ruled out its not a vac leak by pumping 15 psi through the system - air bled out the intake. So I blanked the afms off and did it again, no leaks...

Have also checked the plug onto the AAC motor/solenoid thing - seems firm, but checked to make sure there was a circuit at the ecu - all good.

Checked the fuses - all ok.

Any more ideas? I was sure it had to be a vacuum leak but now i'm 99% sure its not and I'm out of ideas... almost ready to call in the experts

[SargeRX8]

If I have a stockish car and the standard ecu, plug it in see what she does.

[Chris-06R]

Seems to be idling reasonably ok, missing occasionally, if i just start it up and let it sit there. Will start stumbling after a while then cut out after 30seconnds to a minute. My next question - what should the TPS signal be at idle? I have 0% showing on the mfd and even when I crack the throttle to try and stabilise the idle it still shows 0%. I can get the revs to go from about 800rpm to 1200 rpm before the mfd even shows 1%...

PowerFC shows 0.33v from the tps without the throttle depressed but the engine manual says it should be around 0.5v. The idle definately stabilises with the tps voltage that high but then the car is revving about 1200rpm. Can someone check for me if their PFC shows a reading as low as 0.33v on the tps at idle?

[DVS JEZ]

Normally set it to around .44v. U can adjust it easily to rule it out. Its only 2 7mm bolts to loosen the ritate to adjust. Will only need a very small adjustment. Atleast then u will know if that is the cause.

[Chris-06R]

Thanks Jez, adjusted it so that it now reads .45v to ~4v so that at least my mfd shows throttle percentage maxing at 95% instead of 86% like it used to - hasn't fixed the problem though.

I disconnected the AAC solenoid just to see what would happen - no change to idle - should this have an effect if it was connected and functioning?

If I stab the throttle at idle the revs drop quickly before it recovers, however if I gently open the throttle it revs up smoothly. Its obviously not getting enough air (or too much?).

Jez I know you're the central coast but if you're in Sydney today or tomorrow I'd be happy to pay for your time to have a look at everything and see if you can solve it...

[Chris-06R]

Ruled out the PowerFC as the source - Plugged the standard ecu in and it still idled too low...

Tried winding the idle screw in and out a little bit but it didn't seem to have much impact.

I checked the AAC valve signal at the plug - nothing; supposed to be 12v at ignition and ~10v when cold?? Not sure why that was the case - checked continuity between the halfway harness and the plug - all good. So it would seem the ecu is not giving out a signal. I'd like to try the AAC valve test on consult but I don't have that so might be time to call on a workshop...

[DVS JEZ]

I was in sydney actually. In the way back from the blue mountains. Unfortunately i wouldnt have been able to have a look because my missus would have cut my balls off. Is our anniversary. And i was told NO CARS lol

[mr 32]

Again, appreciate all the help, but I still can't find this problem

Have ruled out its not a vac leak by pumping 15 psi through the system - air bled out the intake. So I blanked the afms off and did it again, no leaks...

Have also checked the plug onto the AAC motor/solenoid thing - seems firm, but checked to make sure there was a circuit at the ecu - all good.

Checked the fuses - all ok.

Any more ideas? I was sure it had to be a vacuum leak but now i'm 99% sure its not and I'm out of ideas... almost ready to call in the experts

dont rule out vac leak yet, you can only test part of the system via that method, it doesnt test after the throttle bodies.

Ruled out the PowerFC as the source - Plugged the standard ecu in and it still idled too low...

Tried winding the idle screw in and out a little bit but it didn't seem to have much impact.

I checked the AAC valve signal at the plug - nothing; supposed to be 12v at ignition and ~10v when cold?? Not sure why that was the case - checked continuity between the halfway harness and the plug - all good. So it would seem the ecu is not giving out a signal. I'd like to try the AAC valve test on consult but I don't have that so might be time to call on a workshop...

the ideal scre wont have an effect if you dont follow the idle set procedure, powerfc and stock ecu are slightly diffrent method aswell

do you have a stock mfd or nismo one?