idle speed adjustment

[boggy2006]

hi,

since I got my GQ, the idle speed has been a bit high. It generally stays around 1100rpm and only occassionally drops to 800rpm. The engine speed 'knob' is pushed all the way in and there's plenty of slack in the cable. I've tried adjusting the screw under the throttle cam, but unscrewing it all the way makes no difference. I haven't really noticed a pattern of when it drops to 800rpm, but it's possibly when the engine is much hotter (ie. driving in traffic in high temps). I don't know if it's related, but my temperature guage only goes up to a 1/4, unless I'm standing in traffic at 30C+.
Is there another way to adjust the idle speed? The engine is a TB42E. The idle speed is the same whether running on gas or petrol.
Thanks for any suggestions.

[DX grunt]

Might sound silly, but is your air conditioning running when it idles high? If it is, try turning it off and see if the revs drop.

[YNOT]

Assuming the temperature gauge is somewhere half close to accurate (that's a very big assumption!), you need to get the engine running a proper operating temperature - half way on the gauge.
TB42e has computer controlled idle speed and the computer will raise the idle during warm up. If the engine is not getting above quarter on the gauge then the computer will hold the idle up thinking the engine is still warming up. The first thing I would be doing is replacing the thermostat to get the temp up. Disconnect the battery for 10 minutes minimum after replacing the thermostat to reset the computer.
If the temp does not come up with a new thermostat then I would suspect an inaccurate gauge.

If the idle still stays up with the new thermostat then I would suspect a vacuum leak between the throttle body and the cylinder head or a faulty idle air control valve.

You will probably need to reset the idle throttle stop screw on the throttle body after you fix the fault.

Tony

[boggy2006]

Thanks, I'm more convinced it's temperature related now. I've just left it running at 2000rpm for 10 minutes and the temp guage only just got to over 1/4. However the idle speed had then dropped to 650rpm which seems better. Hopefully it's just the thermostat so I'll replace this. Is there any particular temperature I should go for with the LPG conversion or just the standard one?

[YNOT]

I'd just get a standard thermostat from Nissan.

Tony

[boggy2006]

hmm, seems like the thermostat was a red herring. It still quite often idles above 1100rpm. I can drive it for 30k's and it's idling high. But if I park up for a few minutes, I can come back and the idle will be lower. I checked the resistance of the idle air compensator, adjusted the throttle position sensor and idle switch and checked them, all ok. If I unplug the idle compensator, the revs drop down to about 600rpm, but even then from a cold start it revs high even with the fast idle compensator unplugged. It's so variable, it difficult to keep track of exactly when it is/isn't idling too high (petrol/gas/hot/cold/driven/not driven/etc etc_). I'll keep working on it.

[Stumpjumper]

Did you get a fix for this fast idle boggy? I am asking because I have a TB4.2E and I have the exact same problem.

Marty

[YNOT]

Sounds like a faulty coolant temperature sensor, check this thread; http://www.nissanpatrol.com.au/forum...erature+sensor

Tony

[Stumpjumper]

Thanks Tony, I went to and read Bigrigs posts, I think changing this sensor might be the solution. I shall let you know if it works.

Marty

[Bigrig]

Thanks Tony, I went to and read Bigrigs posts, I think changing this sensor might be the solution. I shall let you know if it works.

Marty

Hope it does mate - sounds like it to me also, so fingers crossed for you.