idle speed adjustment

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.

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.

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

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?

I'd just get a standard thermostat from Nissan.

Tony

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.

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

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

Tony

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

Quote:

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Originally Posted by 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

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

Hey Bigrig!!! The price of the temp sensor has gone up, well here in Adelaide anyhow. Now $63.......jesus wept thats a carton+......
going to pick one up today.
I plan to call at the recycle place and cash in my empties, bins full, 10c a can here. Might ease the pain. Ha ha ha

Quote:

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Originally Posted by Stumpjumper

Hey Bigrig!!! The price of the temp sensor has gone up, well here in Adelaide anyhow. Now $63.......jesus wept thats a carton+......
going to pick one up today.
I plan to call at the recycle place and cash in my empties, bins full, 10c a can here. Might ease the pain. Ha ha ha

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Bloody Nora!!! Hmmm ... Fix the truck versus have a drink ... well, I'm afraid the weekend is upon us, so I'm going 'have a drink'!! If it was Monday and I was making the decision, I'd go with 'fix the truck'!! lmao

Hope it sorts it out for you mate - sounds eerily similar to the problem I had, so my fingers firmly crossed for you.

Wow the new coolant temp sensor has fixed the crappy idle problems........................purrrrrrring like a kitten! only got $20 for my empty beer cans......didnt cover the cost!
Yes I know what you are thinking, if I had drank more beers I would have more money from the empties?

I have stopped my happy dancing cos I just opened the fridge, shock horror!!! an I spent my beer money on that sensor

Quote:

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Originally Posted by Stumpjumper

I have stopped my happy dancing cos I just opened the fridge, shock horror!!! an I spent my beer money on that sensor

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Feeling for you fella - you had a tough call to make, but in true forum fashion, you bit the bullet and took care of the rig - full commendations to you ...

Well, on that note, I'm off for a beer!!!! lmao

Glad it sorted the problem mate!!!

could this be the issue I have with my carby tb42. Mine runs fine on cold start wont run on gas and as soon as it gets a little warn it wont idle at all. I have more details in my members ride thread:
http://www.nissanpatrol.com.au/forum...ry-in-progress)

Quote:

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Originally Posted by evilhighway

could this be the issue I have with my carby tb42. Mine runs fine on cold start wont run on gas and as soon as it gets a little warn it wont idle at all. I have more details in my members ride thread:
http://www.nissanpatrol.com.au/forum...ry-in-progress)

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Hmmmm ... dying on you probably isn't the thermostat temp sensor - doesn't sound quite the same. What about the TPS? Did you adjust it when doing the head??? I'd fiddle with it a bit first ...

The temp sensor going would make it run rough on petrol hot or cold (less noticeable on gas), but worse when hot as it stills thinks its cold and throws fuel into it and idles up ...

I'd try TPS position and back off the AAC screw first (so its idles high) and tweak from there ... if that fails, maybe a small investment into a new temp sensor??

Good luck mate!!

Quote:

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Originally Posted by Bigrig

Hmmmm ... dying on you probably isn't the thermostat temp sensor - doesn't sound quite the same. What about the TPS? Did you adjust it when doing the head??? I'd fiddle with it a bit first ...

The temp sensor going would make it run rough on petrol hot or cold (less noticeable on gas), but worse when hot as it stills thinks its cold and throws fuel into it and idles up ...

I'd try TPS position and back off the AAC screw first (so its idles high) and tweak from there ... if that fails, maybe a small investment into a new temp sensor??

Good luck mate!!

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TB42s's don't run a TPS Bigus as they don't run a ECU.

Thats more a fuel injection thing although not exclusive.

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Originally Posted by patch697

TB42s's don't run a TPS Bigus as they don't run a ECU.

Thats more a fuel injection thing although not exclusive.

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Haha ... true!!! Didn't even note the 'carby' bit - just saw TB42 and went insane with the thumbs on tapatalk!!! lmao

then why does the carby tb42 for auto's have a tps on the opposite side of the carb to the throttle cable?

Its an auto and to it looks like a tps on the opposite side of the carb to where the throttle cable is..
Or is it something different than a tps?

Quote:

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Originally Posted by evilhighway

Its an auto and to it looks like a tps on the opposite side of the carb to where the throttle cable is..
Or is it something different than a tps?

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It is a TPS as such but its only for the Auto trans on board computer or control unit. It has no effect on engine tuning on a TB42s (carby model) as these engines don't run an on board ECU (Engine control unit).

However, engine tuning & shifting the throttle position can effect the way the auto changes & holds gears if not carried out correctly.

hmmm well i havent touched the tps as yet but gonna start it this morning and see if it runs till warm. if so then i know it can run and i would again suspect the head gone after warm up but it a brand new reco one? one thing i did think is when i did the tappits i adjusted them to 0.017 inch instead of 0.015 inch as recomended to give the tappits extra room for heat expansion when warm. The manual that i have says to adjust to 0.008 when cold which is smaller so it doesnt exactly make much sense to me. It still wouldnt really explain the not idling though would it?

Quote:

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Originally Posted by patch697

It is a TPS as such but its only for the Auto trans on board computer or control unit. It has no effect on engine tuning on a TB42s (carby model) as these engines don't run an on board ECU (Engine control unit).

However, engine tuning & shifting the throttle position can effect the way the auto changes & holds gears if not carried out correctly.

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I had to adjust mine - did it manually under trial and error till it was changing correctly ... 0.69 volts once I got it spot on ... That said, mine is a Pintara TPS!! Dodgy as!! lmao

good to know about the tps! The mrs went to work so I went out and tried starting it it started no probs the choke was on (didnt realise) It was running at around 1k no probs but as soon as it started to get a little warm (temp guage didnt even move) she died and not idling again. Maybe i should run some chemiweld and that other head gasket stuff in the bloody thing and piss it off. Ive never had any luck whatsoever with nissan 4wd's I love em but they must think im the funeral director.

Quote:

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Originally Posted by Bigrig

I had to adjust mine - did it manually under trial and error till it was changing correctly ... 0.69 volts once I got it spot on ... That said, mine is a Pintara TPS!! Dodgy as!! lmao

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Yeah but as you said, that was to try & sort out your autos shifting issues. This guy is trying to sort out engine tuning problems.

is there a carby rebuild thread at all that i cant find? Ive been looking but cant seem to find one if there is.

Quote:

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Originally Posted by evilhighway

is there a carby rebuild thread at all that i cant find? Ive been looking but cant seem to find one if there is.

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I think there is but I'd need time to search for it.

When I get a chance at some stage today/night Im going to have a real good read of your wright up to get a grip on what your dealing with but given what I've flicked through so far I don't think your carbies the issue so I'd maybe hold off on that one for the mo.

I can clearly see your pretty hard on the hunt to get this sorted so I'll try getting to it asap & I'll give one of the other members a call to look over it as well to help give some sort of direction. He is a top bloke & an even better mechanic.

Stay tuned.

thanks mate I really appreciate the effort any questians you need to ask to decipher whats happening, please do ask!