Ok guys, it's been a while since I've been on here but I've been busy doing bits to the micra. I was playing around with my idle speed today as my engine has been really lumpy at idle, grumbly with a lot of vibration and a constant whine/drone and when I turn on heavy electrical components such as headlights/heaters or fan comes on the car rumbles like an old tractor while I enjoy a good back massage. These symptoms are at 700-800rppm (+ or -50). If I increase the idle speed to 1000rpm via idle screw however the car idles very smoothly and doesn't whine or rumble/chatter. And it doesn't threaten to die and rumble worse still when an electrical demand is applied. Only downside at this idle speed is car soundsunnatural slightly unnaturally loud but I can live with that. Is 1000rpm the normal idle speed for these cars? A few folk told me their micra idles at 750rpm but mine does not like that speed at all and runs like a bag of spanners and sounds like it too at that rpm. Is their idle differences between coil pack micras (mine) and distributor micras? I'm guessing at 1000rpm my alternator is generating more current therefore headlights fan etc doesn't make the car stumble whereas at lower rpm the genny maybe isn't coping.... And oil pressure is obv higher at faster idle. I have cleaned my iacv out and this is a replacement one that opens and closes fine so no probs there. But my car just will not behave under 1k idle. Possibly my alternator is getting old so not generating enough current therefore spinning it faster is making it generate enough current? What are your thoughts guys... Hit me with all you know about idle
Idle Observations about Idle
- Thread starter SparkyMarc
- Start date
Marc - my coilpack K11 idles OK at about 750-800 RPM - the problem is the car doesn't want to idle at that speed - if you take your foot off the gas, the idle will drop to about 500 RPM and then die.
How did you manage to get the IAC valve off to clean it? It's in a terrible position to access - I'm thinking I might have to take the throttle body off to get at it.
How did you manage to get the IAC valve off to clean it? It's in a terrible position to access - I'm thinking I might have to take the throttle body off to get at it.
Mine did the same and I took the IAC valve off and gave it a good clean out ... put it back together and it still wasnt right ..... so I got a new pack of o rings from B&Q for about £1 and put a new one in that solved it .... seems there was a tiny bit of bypass on the o ring that was making all the difference....
It will now idle at 600 rpm relatively smoothly .... although i think 750/850 ish is better.
Was the o ring that was the main problem with mine .. although it looked fine.
Main difference if o ring isnt good i noticed was needing to turn down the idle screw a lot before idle drops .... whereas now the o ring is right it only needs small adjustments to raise or lower tickover.
It will now idle at 600 rpm relatively smoothly .... although i think 750/850 ish is better.
Was the o ring that was the main problem with mine .. although it looked fine.
Main difference if o ring isnt good i noticed was needing to turn down the idle screw a lot before idle drops .... whereas now the o ring is right it only needs small adjustments to raise or lower tickover.
@Micra Steve- you gotta remove one end of the brake booster hose....the hose that's getting in the way of the lower bolt ...just raise the little clamp clip up the hose (you'll need to squeeze it together to part it first)
And you'll be able to to remove the other bolt. Just remember to refit the end of the brake booster hose when your done and make sure it's tightly on as this is a vaccum line.
Also clean the iacv with carb cleaner and carefully work the little valve while spraying it also, give it a good thorough going over you'll know it's clean/freed off as you'll be able to shake it and hear it rattle mate. Mind put the wee gasket back on with it chances are though that this will be stuck the the mating surface of the iacv and in which case use a veeery thin slither of silicone on mating surfaces before refitting.
If cleaning iacv doesn't work I would try spraying generous amounts of carb/electrical cleaner into the throttle body/ Maf sensor while revving the car directly via the butterfly so it doesn't stall. If it kangaroos/hesitates while driving however I would simply replace the Maf with a denso One.
Sorry for long reply mate just want to give you as much info as possible as I've worked through all these issues and have gotten to know this car inside out almost it seems hehe
A general reply to everyone ....think I've cured my dodgy idle. Seems it was a combination of a badly wired up aftermarket stereo that was grounding where it shouldn't and shorting (my headlights would come on with ignition regardless of stalk switch position and a buzzing noise) and a slightly contaminated Maf. I haven't actually lowered the idle back down to 750 yet but already its much smoother and quieter the engine was making an ominous tappet noise before this it sounded like sticky lifter tick tbh. Sounds fine now. I'll test further tomorrow . I have a spare alternator on hand if it's still crap as that'd be my next guess
Thanks for the tips Marc.
In your first post you said you had a coil pack K11, but I've just noticed that you mentioned an idle screw - the coil pack K11's don't have an idle adjust screw do they?
I know the distributor K11's do - but as far as I know, there is no simple way to manually adjust the base idle in a coil pack K11.
If anyone knows how, please tell me!
In your first post you said you had a coil pack K11, but I've just noticed that you mentioned an idle screw - the coil pack K11's don't have an idle adjust screw do they?
I know the distributor K11's do - but as far as I know, there is no simple way to manually adjust the base idle in a coil pack K11.
If anyone knows how, please tell me!
Steve, the coil pack k11's and the distributor models both have idle screws to adjust base rpm they're just located diffrently. The distributor versions have a pretty big black screw that sits in a housing on the side of throttle body, this screw is flush with the housing/tb so you might not notice it unless your looking. The coil pack k11s however have the throttle screw mounted on the cable guide on the side of the butterfly it's the curved thing the cable sits in. It's below this the screw is tiny though and you'll probably need to move a little cannoster type thing out it's housing to see it with your eyes. Just have a feel around its the only screw of its type on the tb mate.
1 million points to anyone who can tell me exactly the size of the star/spline but needed to remove Mac screws. I don't think it's a spline bit but don't know size . Could be a security star though. It's bloody annoying whatever it is. Requires a very uncommon 'bit' to remove it
Thanks Marc - I'm still learning my way around this, so I'm not sure exactly where you mean - I presume you mean on the OUTSIDE of the throttle body (not inside, where the butterfly valve is)?
Will I need to take the air box off to access the screw?
When you said "Mac" screw, did you mean MAF - it's a TS25 Torx security I believe (didn't need a special tool to remove mine, as the previous owner had kindly ground a slot in it for a normal flat head screwdriver).
Thanks Steve now I can buy JUST the bit I need instead of an entire bit set that might set me back 20 quid (bloody cars costing me enough as it is haha). As for idle screw it is indeed on the outside of throttle body mate, if your facing the bonnet, the butterfly valve cable guide is on the right hand side of the throttle body (you can open and close it with your hands) the idle screw is literally just to the left of this ...here's a picture I stole from msc hehe the red arrow is the screw you want Steve. Adjust it slowly as it takes a few seconds for the ecu to respond to the change. Lastly when your adjusting the idle Steve unplug the throttle position sensor first so it doesn't get reprogrammed . You don't want the tos sensor thinking the accelerator is being pressed when the cars simply idling. Once happy with the idle rpm plug it back in. Hope all this helps once you've done it enough it becomes second nature trust me lol.
Actually just realised the throttle body in picture is slightly different from ours. But it's Still near the gold curved throttle guide mate and the screw looks the same.
Thanks for the input Frank - I thought that the idle should be adjusted via the diagnostic port - but am I doing any harm by using the throttle stop screw?
Is there an easy way to get some software that can make simple adjustments? My OBD2 scanner is quite good, but it just reads data - it can't actually CHANGE anything.
Marc - thanks for the help mate, much appreciated - please get a second opinion on the size/type of the MAF screw though before you buy one - I'm not 100% certain I'm right.
Took the car out to the car boot sale this morning and noticed something interesting - the car was idling a bit better - still very low, but it wasn't stalling.
Then I turned my headlights off and the idle dropped back down to how it usually is!
Definately some clue there - I put my lights on and the revs are noticeably a touch higher - still not perfect, but at least the car is driveable and not cutting out when I stop at junctions.
Is there an easy way to get some software that can make simple adjustments? My OBD2 scanner is quite good, but it just reads data - it can't actually CHANGE anything.
Marc - thanks for the help mate, much appreciated - please get a second opinion on the size/type of the MAF screw though before you buy one - I'm not 100% certain I'm right.
Took the car out to the car boot sale this morning and noticed something interesting - the car was idling a bit better - still very low, but it wasn't stalling.
Then I turned my headlights off and the idle dropped back down to how it usually is!
Definately some clue there - I put my lights on and the revs are noticeably a touch higher - still not perfect, but at least the car is driveable and not cutting out when I stop at junctions.
that shows your idle control valve is working then steve, try half a turn in, on that throttle stop screw then
Sounds like good news. So, if this shows my IAC valve is working correctly, is there any point in me trying to get it off to clean it?
Found the throttle stop screw, but I haven't adjusted it yet.
Do I turn it clockwise or anti-clockwise to raise the idle?
Hello Frank. Did you design these cars ? information highway or what !!!!thats the throttle stop adjustment tho marc, the coilpacks have a stepper motor idle control valve that should be set via the diagnostic port iirc (and it wont function properly if that throttlestop screw is too far in)
Nissan Datascan seems to have the ability to perform various adjustments - one of which is "base idle adjust".
I'm sure it's not the same as the full Nissan Consult that you would find at a dealership or Nissan specialist - but a lot cheaper of course.
I'd like to know that myself. Anyone?
Re: My idle problem
I think I may have figured out what's going on.
Using my OBD2 scanner today, while the car was idling (when warm), the live data showed my TPS reading at around 6% - I think I'm right in saying that it should be at 10%, plus or minus a bit.
I know that with the earlier non-coilpack K11's, the TPS is set to read between 0 and 5 volts - and that the voltage at idle should be 0.5 volts (or at least somewhere between 0.4 and 0.6 volts).
So assuming the same is true with the later K11, my reading of 6% suggests a reading of 0.3 volts.
If so, the ECU is not seeing the 0.5 volts that it expects to see when idling and I need to adjust it - I know the earlier TPS could be manually adjusted, but the later TPS on the Bosch TB is factory set.
Am I on the right track here? If so, what are the options (if any) for adjusting the TPS - apart from the obvious "take it to a Nissan dealer" of course!
I'll get the TPS off and give it a clean first of all, when I've borrowed the necessary tool from my neighbour - hopefully that might do it and I won't need to adjust it.
Just noticed my throttle cable seems slightly loose - I think there is supposed to be a little slack in it, but even bearing that in mind it still looks like it could be tightened just a touch.
Would a slightly loose throttle cable cause my TPS reading to be at 6%, rather than the ideal 10% at idle?
Would a slightly loose throttle cable cause my TPS reading to be at 6%, rather than the ideal 10% at idle?
