Unstable/fluctuating idle - K-Series

v-man · 6th August 2015, 09:19

After my recent issue with camshaft sensor - http://www.the75andztclub.co.uk/foru....php?t=220552m - I thought my 1.8 45 (not 75) would present no more issues for a while. Seems I was wrong as on Tuesday driving to work the engine was idling at approx 2000 rpm, I did stop and restart but it was the same. However the drive home was different, it still wasn't idling at the correct speed, but it wasn't as high as in the morning. When I reached my garage and the engine warm the idle speed was fluctuating by approx 300 rpm, dipping down to 750 or so (almost cutting out) and then picking back up to 1050, then down again and so on.

Haven't driven it since, just in case it got worse.

There are no stored error codes, according to Torque app.

Am I correct in thinking the idle air control valve is the culprit?

Thanks for reading.

suzublu · 6th August 2015, 09:34

Ian, try resetting the iacv by turning the ignition on but don't start the engine, then press the throttle 5 times quickly, turn off then restart the car. Might help.

v-man · 6th August 2015, 09:56

Quote:

Originally Posted by suzublu

Ian, try resetting the iacv by turning the ignition on but don't start the engine, then press the throttle 5 times quickly, turn off then restart the car. Might help.

Thanks Ronnie, have tried that already. Though I think that is the procedure to reset the throttle position sensor.

roverbarmy · 6th August 2015, 11:54

Check for inlet manifold leaks/ connecting pipes loose/perished etc.

pletevl · 6th August 2015, 13:52

Has anyone ever adjusted (turned) the throttle position screw on the throttle body ?

stevestrat · 6th August 2015, 20:12

Quote:

Originally Posted by pletevl

Has anyone ever adjusted (turned) the throttle position screw on the throttle body ?

If its the screw I am thinking about it adjusts the stepper motor and should be done while connected to a T4 to monitor idle speed etc.

RogerHeinz57 · 6th August 2015, 20:41

With engine at running temperature, spray some brake cleaner about all the inlet seals / joints first. For those not in the know, this should tell if there is an air leak caused by a failed sealing joint, the engine would change running when you spray near the culprit , OBD won't find this out.
Start with basic stuff that costs pence to try out before spending £ at a garage who will probably have your trousers down ££££££££.
Also fiddling with base settings on throttle housing wont effect a proper fix, unless the engine has been running like this for a while with a replaced body fitted.
The skills needed are basic on this and should be easy to practice to find the problem, then effect a proper repair from a proper diagnosis.

pletevl · 7th August 2015, 09:27

Quote:

Originally Posted by stevestrat

If its the screw I am thinking about it adjusts the stepper motor and should be done while connected to a T4 to monitor idle speed etc.

Exactley, this is why I asked, my ZR went in to my local MG Rover garage (in 2004) because of bad engine vibrations with the aircon on. They started playing around with this screw to try to up the idle speed.

A couple of days later, the car would idle eraticaly, reving up and down on its own in neutral at junctions etc.

Took it to another garage who set it back up on T4 properly.

Pete.

v-man · 15th August 2015, 13:18

Quote:

Originally Posted by stevestrat

If its the screw I am thinking about it adjusts the stepper motor and should be done while connected to a T4 to monitor idle speed etc.

I know better than to mess with that screw and yes you are correct a T4 session is needed to set it correctly.

Quote:

Originally Posted by roverbarmy

Check for inlet manifold leaks/ connecting pipes loose/perished etc.

Thanks for the tip.

Quote:

Originally Posted by John H

With engine at running temperature, spray some brake cleaner about all the inlet seals / joints first. For those not in the know, this should tell if there is an air leak caused by a failed sealing joint, the engine would change running when you spray near the culprit , OBD won't find this out.
Start with basic stuff that costs pence to try out before spending £ at a garage who will probably have your trousers down ££££££££.
Also fiddling with base settings on throttle housing wont effect a proper fix, unless the engine has been running like this for a while with a replaced body fitted.
The skills needed are basic on this and should be easy to practice to find the problem, then effect a proper repair from a proper diagnosis.

Thanks John for the wise words.

Now quick update: Having not used the car since my last post I went around my rented garage today to see what I could find. Started up as normal, no sign of weirdness. Left it idling while I checked the tyre pressures, still ok. Had a quick check around the pipes and wiring, couldn't see anything. Oiled the exposed end of the throttle cable, took off the air filter and multiple times sprayed some Wynns carb/injector cleaner into the pipe leading to the throttle body, it was definately going through as it was clearly affecting the engine rpm, indeed at one point I did stall it. Put the air filter back and went for a quick 10 mile drive, no issue at all. Wondering if the ambient temperature being cooler today is masking a sensor issue, which manifests when hot.

Ste.Sales · 15th August 2015, 18:13

I had a similar issue with my zr, turned out to be a faulty throttle position sensor.

6th August 2015, 09:19	#1
v-man I really should get out more....... Ford Fezza Poverty Spec & ? Join Date: Dec 2010 Location: Lincolnshire Posts: 2,892 Thanks: 526 Thanked 349 Times in 275 Posts	Unstable/fluctuating idle - K-Series After my recent issue with camshaft sensor - http://www.the75andztclub.co.uk/foru....php?t=220552m - I thought my 1.8 45 (not 75) would present no more issues for a while. Seems I was wrong as on Tuesday driving to work the engine was idling at approx 2000 rpm, I did stop and restart but it was the same. However the drive home was different, it still wasn't idling at the correct speed, but it wasn't as high as in the morning. When I reached my garage and the engine warm the idle speed was fluctuating by approx 300 rpm, dipping down to 750 or so (almost cutting out) and then picking back up to 1050, then down again and so on. Haven't driven it since, just in case it got worse. There are no stored error codes, according to Torque app. Am I correct in thinking the idle air control valve is the culprit? Thanks for reading. __________________ Report potholes, flytipping, broken streetlights - www.fixmystreet.com Find cheaper diesel/petrol - www.petrolprices.com 2001 Rover 45 1.8 Impression S owned for 15 years, now scrapped.

6th August 2015, 11:54	#4
roverbarmy This is my second home Roverless + 1.7D Sportage Join Date: Aug 2014 Location: East Norfolk Posts: 7,050 Thanks: 729 Thanked 2,021 Times in 1,449 Posts	Check for inlet manifold leaks/ connecting pipes loose/perished etc. __________________ Oil in my veins!

6th August 2015, 20:41	#7
RogerHeinz57 I really should get out more....... A Reasonably Priced Car Join Date: Jan 2014 Location: Burton Latimer Posts: 2,530 Thanks: 408 Thanked 1,064 Times in 712 Posts	With engine at running temperature, spray some brake cleaner about all the inlet seals / joints first. For those not in the know, this should tell if there is an air leak caused by a failed sealing joint, the engine would change running when you spray near the culprit , OBD won't find this out. Start with basic stuff that costs pence to try out before spending £ at a garage who will probably have your trousers down ££££££££. Also fiddling with base settings on throttle housing wont effect a proper fix, unless the engine has been running like this for a while with a replaced body fitted. The skills needed are basic on this and should be easy to practice to find the problem, then effect a proper repair from a proper diagnosis. Last edited by RogerHeinz57; 6th August 2015 at 20:45.. Reason: Needed to edit.

6th August 2015, 09:34	#2
suzublu This is my second home rover 75 1.8 vvc club se wedgwood blue Join Date: Aug 2009 Location: Seaton Carew Posts: 26,922 Thanks: 65 Thanked 7,142 Times in 4,642 Posts	Ian, try resetting the iacv by turning the ignition on but don't start the engine, then press the throttle 5 times quickly, turn off then restart the car. Might help.

6th August 2015, 13:52	#5
pletevl Posted a thing or two rover 75 cdti(rhd), MG ZR(lhd), MG TF(lhd), MG TF(rhd), mini mpi (lhd), Renault megane III (awful) Join Date: Mar 2014 Location: East of France Posts: 1,282 Thanks: 124 Thanked 114 Times in 93 Posts	Has anyone ever adjusted (turned) the throttle position screw on the throttle body ?

15th August 2015, 18:13	#10
Ste.Sales Avid contributor Rover 75 Saloon Join Date: Jan 2015 Location: Preston Posts: 233 Thanks: 9 Thanked 37 Times in 35 Posts	I had a similar issue with my zr, turned out to be a faulty throttle position sensor.