Ropey idle

[Dodger]

New boy in school here. I bought my 1992 S13 auto six or seven weeks ago.....goes like stink (as my tame garage man suggested). It starts fine and runs smoothly from cold until it's warmed up and then the idle turns lumpy. It's not horrific but irritating since it runs so brilliantly otherwise. It'll idle at the 850 mark for say 10 sex and then drop 100 rpm off for a second and then pick up again. Mr Garage (as mentioned above) even drove it round to his mate at a Nissan main dealer, who plugged it into the diagnostic gizmo and couldn't find a fault. Previous experience suggests it's idling as if the cold start isn't dropping out (like my old Volvo 244 idled when the choke wasn't all the way in)- I wondered if a coolant temp. sensor replacement might be in order. Any views?

[Nathan_200sx]

Howdy, Mines done that for around 2 years now, I was told it was the idle sensor. so I havent done anything about it. it seems to idle ok then go high and then drop low and the ok again. as there was no detrimental effect to the car I've just left it.

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Nathan
Red S13 Mongoose, K&N T3 280ish BHP http://mysmilies.com/smilies/cwm30.gif
Empty bank account

[Paul_S13]

Your car is scary Nat, "its alive Jim but not as we know it" http://300zx.co.uk/200sx/ubb/biggrin.gif

[olly200sx]

The idle is controlled by a number of factors, mine did the same and I changed the temperature sensor, no good, I then took out and thoroughly cleaned the AAC valve and this worked wonders my car now idles with perfection even though I have an atmospheric dump valve that leaks at idle !!!

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S13 - Lots of Mods

[dave_s13]

My idle's a tad lumpy n'all

so

whats an AAC valve, where is it, how do you remove it and what did you clean it with?????

[Ripper]

Have you got Air-con?

That kicks in and out...


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Ripper

Grey 1993 S13

[dave_s13]

No air con unfortunatly (its furkin boiling today, can't wait to sit in traffic on the way home and get roasted alive).

Am I correct to assume the AAC valve is part of the air con system?

[David_S14]

Idle speed is controlled through the adjustment of the amount of air which bypasses the throttle valve via the IACV/AAC valve. The IACV/AAC valve cycles on/off according to a signal from the ECU.
The ECU gets its info from the cam position sensor and so varies the cycle of the IACV/AAC to get the desired idle speed.
The valve is above the inlet manifold on mine right on top on a bracket (level with no. 3 cylinder)


David Cater
1995 S14
K&N,Mongoose,HKS pump,Blitz FATT-S
RLTC (when I get it fitted http://300zx.co.uk/200sx/ubb/wink.gif ).

[This message has been edited by David_S14 (edited 25-06-2001).]