Engine 'hunting' on idle

ceb · 26th August 2010, 14:39

Good day my fellow keepers of the faith.

Had the pleasure of sitting in traffic jam on the M25 this morning, when I got clear I was then sitting in heavy traffic on the run in to North London when I noticed that the engine/revs were 'hunting' between 600 and 14-1500 rpm, it would drop down then run straight up then back down etc. I put the dash in to diagnostics and checked the temperature (just in case!) and all seemed well, blipped the throttle a few times but it went back to hunting once the revs had settled. On the run back made a point of putting the box in sport mode and running the engine up through the revs and it seems to pick and run fine, no miss fires etc so any pointers/suggestions of cause or what to check etc. would be appreciated.

Cheers,

ceb

Phil · 26th August 2010, 20:46

You can reset the stepper motor, I forget the procedure but IIRC it is rapidly pumping the throttle pedal to the floor with the ignition on but the engine OFF about 15 times, maybe someone else can clarify.

Andyd358 · 26th August 2010, 21:38

Had a similar thing on mine (CDTI) and after 2 deisels had alook turned out my fan wasnt working properly and the Aircon was causing the hunting when idle.

Phil · 26th August 2010, 22:06

Quote:

Originally Posted by Andyd358

Had a similar thing on mine (CDTI) and after 2 deisels had alook turned out my fan wasnt working properly and the Aircon was causing the hunting when idle.

That is worth checking out Ceb, if the a/c is on with no fan the compressor will go bonkers.

ceb · 26th August 2010, 22:38

Quote:

Originally Posted by Phil

That is worth checking out Ceb, if the a/c is on with no fan the compressor will go bonkers.

Will do, although I'm pretty sure that all is well in that dept. I had a Jules special fan replacement done when I first got it and I was watching the dash diagnostics temp and am pretty sure the fan was cutting in o.k. as temp was dropping back from 99/102 to 94 or so and I'm 'sure' I could hear the fan cutting in, I was stationary in traffic for a good long while (45 mins) so would have expected temp. to go really high if the fan was playing up?, but I'll do a 'demist' check on the fan again in the daylight anyway and do a stepper reset.

Cheers guy's.

ceb

jcwatrichmond · 27th August 2010, 07:57

Amongst many other causes, that sort of idling hunting can be caused by ignition problems; plugs or leads or coils etc.

JCW

26th August 2010, 14:39	#1
ceb Loves to post Rover 75 Saloon V6 2.5 Club SE Auto 2001 (X) Join Date: Nov 2009 Location: Stansted Posts: 374 Thanks: 0 Thanked 0 Times in 0 Posts	Engine 'hunting' on idle Good day my fellow keepers of the faith. Had the pleasure of sitting in traffic jam on the M25 this morning, when I got clear I was then sitting in heavy traffic on the run in to North London when I noticed that the engine/revs were 'hunting' between 600 and 14-1500 rpm, it would drop down then run straight up then back down etc. I put the dash in to diagnostics and checked the temperature (just in case!) and all seemed well, blipped the throttle a few times but it went back to hunting once the revs had settled. On the run back made a point of putting the box in sport mode and running the engine up through the revs and it seems to pick and run fine, no miss fires etc so any pointers/suggestions of cause or what to check etc. would be appreciated. Cheers, ceb

26th August 2010, 20:46	#2
Phil This is my second home Rover 75 CDT Connoisseur SE Join Date: Nov 2006 Location: Wales Posts: 12,227 Thanks: 469 Thanked 523 Times in 241 Posts	You can reset the stepper motor, I forget the procedure but IIRC it is rapidly pumping the throttle pedal to the floor with the ignition on but the engine OFF about 15 times, maybe someone else can clarify. __________________

26th August 2010, 21:38	#3
Andyd358 Posted a thing or two JAguar X-Type 2.0d Sport Join Date: Jan 2010 Location: Bedlington, Northumberland Posts: 1,902 Thanks: 2 Thanked 15 Times in 8 Posts	Had a similar thing on mine (CDTI) and after 2 deisels had alook turned out my fan wasnt working properly and the Aircon was causing the hunting when idle. __________________ This was My MGZT [SIGPIC][/SIGPIC] Going to miss driving it Support Our Troops http://www.helpforheroes.org.uk/

27th August 2010, 07:57	#6
jcwatrichmond Loves to post Rover 75 1.8T 2003 Club SE Join Date: Jan 2009 Location: Solihull, Posts: 370 Thanks: 0 Thanked 0 Times in 0 Posts	Amongst many other causes, that sort of idling hunting can be caused by ignition problems; plugs or leads or coils etc. JCW