micra fast idle when at running temp

[CMF_micractiv]

Hi to everyone, and thanks for making this wonderful website available to micra drivers out here. It's great that there is a place like this to find solutions to problems.

I've just bought a 1.4 activ 2001 reg. The car is great in every respect apart from one - when it is at running temp the idle speed is far too fast. I have no rev counter fitted, but would estimate it to be about twice the speed it should be. My brother has an older 1.3 and that idles at around 750rpm i think.

When driving the car it performs great. It starts and runs at a slow idle speed from cold in the morning, has clean acceleration throught the range, no stalling, no lurching, no hiccupping, no misfires, but it revs fast when i come to a stop at junctions etc.

I also feel that it is using more fuel than it should, but haven't measured this yet.

Has anyone here had a similar experience? I've read through some of the threads about throttle bodies failing, and am hoping that mine is not faulty as it's going to cost if it is. I think this one's a bosch, but ill have to confirm that.

Any help would be muh appreciated. Thanks.

 

[CMF_Paul Smith]

Hi it doesn't sound like a throttlebody failing however you could try adjusting the idle screw with an alun key. This screw is located to the back left hand side of the throttlebody as you look at the engine.

if that is no good and doesn't solve it? Does the car ease down slowly or just stay at high revs? my engine if i have been going well takes a few seconds to settle down at junctions.

Let me know how you get on?

Thanks
Paul

 

[CMF_nz_aj]

EVLGTI has a similar problem with his, it idles around 1250rpm most of the time.
There is a procedure for adjusting the idle speed, you don't just turn that screw

 

[CMF_Yom]

Yeh it'll probably different for the 1.4L as well> Different engine management!

 

[CMF_micractiv]

Thanks for all your replies. I'm going to have a good look around the throttle body this weekend to see if I can locate the problem.

I will look for the idle screw if there. I think the body is a Bosch model, will confirm that on Saturday. Am hoping my Haynes manual arrives today.

I will keep you updated as to how I get on. It's really annoying, as in every other respect the car runs fine. It is very quick through the gears and runs smoothly through the entire rev range.

The revs just stay high on tickover, not coming down at all, but very occasionally there is a momentary drop in the revs as if it's about to settle, then it's back up again.

 

[CMF_micractiv]

Well, I couldn't find anything, and that was after a lot of studying and seraching. So, took micra to Nationwide Autocentre for diagnostic check. £27.50 later, they couldn't find a fault, but also couldn't fix the fault.

Narrowed it down to a possible fault with the engine temp sensor, which they said would have to come from Nissan dealer.

Ordered part, fitted it today, no change, so I've booked it in to Nissan Dealer for check up. Nearest appt is in two weeks, so I've got a long miserable wait, with a car that revs its nuts off when hot.

Word of warning to anyone considering buying a car from Oldham Car Sales - DON'T! They're rip off con merchants, and they have no after sales care at all.

Will keep you updated as to the outcome, good or other.

 

[CMF_siblinghk]

micractiv WROTE:

"Well, I couldn't find anything, and that was after a lot of studying and seraching. So, took micra to Nationwide Autocentre for diagnostic check. £27.50 later, they couldn't find a fault, but also couldn't fix the fault.<BR><BR>Narrowed it down to a possible fault with the engine temp sensor, which they said would have to come from Nissan dealer.<BR><BR>Ordered part, fitted it today, no change, so I've booked it in to Nissan Dealer for check up. Nearest appt is in two weeks, so I've got a long miserable wait, with a car that revs its nuts off when hot.<BR>

hi guys, my micra 1.3 has similiar problem in the other way. it also run prefectly in every other respect except the idle speed stay low at around 600rpm when it is at running temp but no stalling. i have checked 2 garages and i was told no proble with the exhaust and air filter. ive also booked it in to Nissan Dealer for check up in 2 weeks. so i just hope u can update me what u found......thanks in advance

 

[CMF_asdamepop]

hey
from whats been described i think i might be a stuck AAC valve.

mine used to start from cold very slowing <400rpm then goes upto 1100rpm once warm, adjusting the idle screw didn't fix the core problem

i recently resolved it by basically cleaning out the AAC valve (idle control valve device located at front of TB, it works like an automatic choke). it was clogged by years of carbon buildup.

once it was clean and the mechanism working freely, pop it back on started car, had to turn down the idle screw adjuster all the way cos it revved more than before at first, now it's runs perfect

on cold start the engine instantly goes up to 1000rpm to warmup as it should (AAC opens up), then once it's warmed up it lowers down to 600rpm (AAC closed) bang on spec.

you could check it out on my MSC thread
http://micra.org.uk/t13606-p9-cylinder-head-prob.html

so i'd advise cleaning the AAC valve first to get that workin properly, then if needed the idle screw could be turned to adjust the idle range

 

[CMF_Yom]

Guys the other thing the CG motor uses is a wax pellet that expands as the coolant heats up (there is coolant flow to the rear of the TB).

the wax is contained in that cylinder looking part and as it heats up it expands it pushes the throttle butterfly closed (where the idle control screw comes into play). When the wax is cold (at ambient temperature) the wax contracts and the TB is angled open slightly.

So yeh the idle control screw should NOT be used to adjust cold idle. It is only there to control idle at operating temp. Sorry if this post is slightly confusing. Its a pretty simple setup if you think about it.

And YES the wax pellet will not last forever. It works in the EXACT same way your thermostat does. It WILL wear out eventually. When it does you will have to disable it and put up with a possibly crappy idle when cold and also difficulty starting it when cold. Alternatively you could replace the TB.

 

[CMF_micractiv]

Thanks for all your input on this. Just been to my local Nissan dealer in Abergele today, where they tested the car to find the fault.

From what they said they found no fault codes on computer, but said that the most probable cause of idle speed problem is the throttle body, which they have quoted me £642.86 including parts, labour and VAT, to fix.

I think this is veyr expensive, and anyway i don't have that amount of money to throw around at the moment. And I'm not convinced that they know 100% what the problem is. I think that they've eliminated everything else, and that they suspect one of the component parts in the throttle body, but as with all so called modern day mechanics, they're not prepared to searhc further or fit parts to parts, they're just out to fit parts to cars.

So I'm going to have a go at cleaning the throttle body this saturday as I've got nowt to lose, and if that fails i'll buy one myself for a third of what they've quoted and fit it myself.

Are there any real mechanics left in the world, i wonder? I mean ones that work for major dealer networks. I doubt it very much. £52 just to be told after 30 minutes what i already suspected.

I'll keep you updated as to how i get on.

And i'll reiterate, don'y what ever you do buy a car from Oldham Car Sales in Manchester, because they'll stuff you up just like they did me.

 

[CMF_asdamepop]

£642 for a TB?! that's insane. prob cost more than my cars market value.

it's one reason why i'd rather learn to fix/overhaul my own car rather than let a garage, unless it's a specialist job that i can't do of course.

good luck with the TB overhaul

 

[CMF_nz_aj]

Cleaning the AAC valve reminds me of another K11 that had problems a few years ago. Cleaning it out made the same difference as described & the idle speed screw needed adjusting afterwards.

Is that wax pellet arrangment the thing that screws into the block at the dizzy end that has two vacuum hoses coming off it? I've seen this on 1992 to ~1995 Jap spec CG motors. After that it appears to have been left off.

 

[CMF_Yom]

Nah the wax pellet to adjust idle on mine and the jap CG13 i have are on the back of the throttle body. There's coolant hoses going to it and it adjusts the throttle butterfly stop.

 

[CMF_Brendon]

idle control valve could be playing up as well.

my gtir has same problem. when warm idles around 1400rpm. is rather annoying

 

[CMF_micractiv]

Well, after suffering for weeks with a problem tickover, I'm happy to be able to report that it's finally cured.

Ordered a remanufactured Bosch throttle body from www.bba-reman.com on an exchange basis at £284.00 and fitted it myself this evening.

My Micra is now runing better than ever, and has a nice low steady tickover speed.

At least now I can start enjoying driving it, and should see an improvement in fuel economy.

I would like to know exactly what part of the throttle body was faulty, but can't be sure. I suspect the aac/idle speed control, but even if I had known, I doubt I would have been able to source just the individual components on the Web.

I guess that if you have a problem with tickover speed, staring or stalling, it saves a lot of wasted time, misery and heartache to just go out and buy a remanufactured throttle body and have done with it.

Thanks again for all your helpful comments, much appreciated.