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The mkiv Supra Owners Club

Idling issue (hot)


AlexM

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I bought my car from carl0s, which previously had some idling issues. I was of the understanding that everything was fixed before I bought it - but it seems not.

 

The car idles at ~250rpm when hot, and struggles to keep itself alive (It 'hunts' and the rev counter fluctuates slightly). At SRR it refused to idle at all, with the car starting fine then the revs slowly dropping down to 0. LeeP had a look and adjusted the throttle stop to keep it running, and noticed that a second stopper was missing (I think Ryan mentioned it was just to take the slack out of the cable? Not sure I caught what he said correctly).

 

Up until this point I had only noticed the problem after a long journey (30mins+, with some motorway running).

 

I dropped it in to Silverstone Garage before Christmas, they reset the throttle stops to the correct position (and replaced the missing one), found the oil filter to be loose, so checked/tightened that and changed the oil, and refitted the upper radiator hose as it wasn't on correctly. They didn't notice the problem after that, having given the car some test drives and left it running for some time - so told me it was fixed. I drove it home, parked on my driveway... and the revs dropped to about 200. :rolleyes:

 

It now seems to have the issue more frequently, as even a 5 minute journey to the petrol station can result in the idle dropping right down..

 

The car will be going back to Silverstone Garage after the New Year as I don't have bits and pieces lying around to troubleshoot. However what should I/we be looking for? Carl (previous owner) seems to have spent considerable time and effort in trying to fix the problem, and all the obvious avenues look to have been investigated already..

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  • 3 months later...
Guest SupraGTE

same here, changed idle control valve, leads, cap, sparkplugs, adjusted tps and the problem wenayt away for a week , only short trip (5km) then today a long trip and now it is back :(

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I had same broblems last summer, suddenly rpm ~250, mostly when driving in city (waiting for traffic lights... = idle). I cleaned idle control valve and it stopped :)

 

How about that last thing, ecu? Isn`t the ecu controlling idle control valve? When i got airleak in intake manifold (leak in those small pipes between intake manifold and engine) rpm went ramdomly between 1500-2000rpm on idle.

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Just a thought, Poss might be the rubber injector seals in the cylinder head. Thinking could be that they are perished and opening up when hot?, making it run lean/ poor idle when hot.

 

May be worth checking the spark plugs to see what state there in may give an indication as to what maybe at fault , i.e lean or rich.

 

Although from what I've read there's no indication of misfire, so I may be wrong.

 

Only other thought would be a wiring fault or MAP sensor. Had an IS200 which had similar symptoms due to an aftermarket piggyback ecu fitted, which tapped into the ECU end wiring for the MAP sensor / Temp sensor / Cam position. removed the aftermarket ECU and repaired the wiring back to OEM, ran just fine , but it's just a thought.

Edited by GreaseMonkey (see edit history)
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I had same broblems last summer, suddenly rpm ~250, mostly when driving in city (waiting for traffic lights... = idle). I cleaned idle control valve and it stopped :)

 

How about that last thing, ecu? Isn`t the ecu controlling idle control valve? When i got airleak in intake manifold (leak in those small pipes between intake manifold and engine) rpm went ramdomly between 1500-2000rpm on idle.

 

any pics of were this is and how to clean it pls

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i had this on my 300zx for a while,

 

car just woundt idle at all after i transplanted the engine into another shell.

 

i knew the ins & outs of the engine, coudnt see/find any vacuum leaks,

 

it would idle fine when cold, but not when warm

 

(idle valvs have cold & hot part to them, which is why idles high when cold)

 

i removed the valve, cleaned it, re-fitted it. still nothing.

 

i fixed the idle problem.........

 

by just turning up the idle screw! thats what its there for at the end of the day!

 

just turn it up, and not just a little tiny bit, give it a few good turns when the cars warm, then just adjust bit by but until idles on about 900rpm

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  • 4 months later...

hi

i have nearly the same probleme

ok when cold , but hesitating (200?250 rpm) and even dies in traffic or after high rpm drop (like when passing gear slowly; 4000rpm to ... 0 )its awfull

have already cleaned the iacv but it come back ; will check for vacuum leaks!

 

did you solve yours??

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  • 1 month later...
Guest Dasher220

Can someone post a pic of where the IACV is, i have the same problem and have been told to clean this valve but ive got no idea where it is.

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