Go Back   The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club Forums > Technical Help Forum
Register FAQ Image Gallery Members List Calendar Mark Forums Read
Notices

Reply
 
Thread Tools Display Modes
Old 19th January 2021, 19:49   #1
biffa75
Trader
 
biffa75's Avatar
 
Mk1 2004 tourer cdti + MK1 2003 Saloon CDT

Join Date: Nov 2015
Location: west yorkshire
Posts: 481
Thanks: 106
Thanked 91 Times in 57 Posts
Default 75 V6 fluctuating idle when warm

Hi folks,

Having an intermittent issue with our V6. Once the engine is warm, coming to a junction etc when the engine is at idle the revs can vary from around 850rpm to 300 or there abouts, continually going up and down until it cuts out or the throttle is used.

The thermostat had recently been changed but found its opening at around 82°c (not sure if this is likely to cause the issue).
Both breather hoses were replaced as both broke ( the usual one that brakes near the alternator and the other one that is seated next to it when connected to the cam cover).

Can't hear any vacuum type noises from under the bonnet and drives fine otherwise. I've had a read around and believe it maybe down to the throttle position sensor?..

Any advice is welcome
Thanks

Rob
__________________
"A Rover doesn't breakdown.... It merely fails to proceed"
biffa75 is offline   Reply With Quote
Old 20th January 2021, 09:45   #2
Canonite
This is my second home
 
BMW 330d Tourer, MG ZT 180 SE XPG, VW Polo 6R 1.2 TDI Bluemotion

Join Date: Jul 2011
Location: York
Posts: 6,020
Thanks: 363
Thanked 574 Times in 319 Posts
Default

What did they remove when they replaced thermostat?
If they removed the upper inlet plenum, is that seated on the green O rings properly?

Is the flexi hose from the TB to the air box seated correctly?
I’ve seen loads where the rubber underneath is folded so it looks okay from above but massive hole underneath.

You can also buy an Idle Air Control Valve kit, this renews most IACV parts and is a simple easy to do job.
Canonite is offline   Reply With Quote
Old 20th January 2021, 11:48   #3
trebor
This is my second home
 
trebor's Avatar
 
Rover 75 CDTi Connoisseur SE & MG ZT Saloon 190

Join Date: Jun 2007
Location: Coven
Posts: 12,516
Thanks: 526
Thanked 1,877 Times in 885 Posts
Default

A friend of mine John had a similar issue with V6 erratic tickover and it will cost nothing to try his fix, reset the potentiometer, put ignition in position 2 and press down on the accelerator 10 times, has to be worth a try
__________________
www.midlandsnanomeets.co.uk

Robs Car Gallery

Coven near Wolverhampton WV9

2000 Cowley Built Rover 75 2.0 V6 Club SE/ Atlantic Blue/ Sandstone/Walnut (daily driver)
2003 Land Rover Freelander 1 TD4 HSE Helsinki Blue/Black Leather (swmbo daily driver)
trebor is offline   Reply With Quote
Old 20th January 2021, 12:43   #4
biffa75
Trader
 
biffa75's Avatar
 
Mk1 2004 tourer cdti + MK1 2003 Saloon CDT

Join Date: Nov 2015
Location: west yorkshire
Posts: 481
Thanks: 106
Thanked 91 Times in 57 Posts
Default

I removed the upper inlet manifold when doing the thermostat. I fitted new o rings supplied by dmgrs.

I've tried the throttle reset procedure and it doesn't appear to have worked.

The hose that runs to the throttle body had folded when I was fitting it was a bit of a faff to get it to fit without it folding but it's now fitted without it being folded up.

I've seen the iacv kit that Rimmer bros sell.. may have to buy one then..

I have noticed though that when the revs are all over the place when it should be a steady idle, if I put my foot behind the throttle pedal and pull the throttle pedal up the idle returns to normal and is okay until the throttle is used again.
Thanks
Rob
__________________
"A Rover doesn't breakdown.... It merely fails to proceed"
biffa75 is offline   Reply With Quote
Old 20th January 2021, 13:04   #5
edwardmk
Gets stuck in
 
edwardmk's Avatar
 
MG ZT 260, Rover 75 Connie SE auto

Join Date: Feb 2013
Location: Redruth
Posts: 982
Thanks: 1,324
Thanked 399 Times in 271 Posts
Default

Quote:
Originally Posted by biffa75 View Post
Hi folks,

Having an intermittent issue with our V6. Once the engine is warm, coming to a junction etc when the engine is at idle the revs can vary from around 850rpm to 300 or there abouts, continually going up and down until it cuts out or the throttle is used.

The thermostat had recently been changed but found its opening at around 82°c (not sure if this is likely to cause the issue).
Both breather hoses were replaced as both broke ( the usual one that brakes near the alternator and the other one that is seated next to it when connected to the cam cover).

Can't hear any vacuum type noises from under the bonnet and drives fine otherwise. I've had a read around and believe it maybe down to the throttle position sensor?..

Any advice is welcome
Thanks

Rob
I shall watch this thread with great interest. When my V6 2.5 is hot, she idles around 900-1000. If I drop her out of gear and coast down a hill, the idle speed often initially 'hunts between 1200 and 1900 revs. Just failed her MOT( rear indicators wrong colour and front anti-roll bar bushes )........yet nothing about emissions which I was expecting. Currently the fuel consumption is slightly higher than the V8 so I'm glad not to be a road warrior nowadays. I can't hear any vacuum issues either and the hoses all look very good. Nevertheless, contemplating trying a smoke test when I get the chance. Engine has 140k on the odometer. It seems to pull well with no hesitation on acceleration and has never cut out on me.
edwardmk is offline   Reply With Quote
Old 20th January 2021, 13:58   #6
COLVERT
This is my second home
 
R75 Saloon.

Join Date: Feb 2009
Location: France/or Devon.
Posts: 14,003
Thanks: 3,851
Thanked 2,167 Times in 1,816 Posts
Default

Reference post 3.----If your car has a potentiometer then it sounds like you need to renew it if lifting the throttle pedal cures your tick-over problem.
COLVERT is offline   Reply With Quote
Old 20th January 2021, 14:51   #7
SD1too
Doesn't do things by halves
 
SD1too's Avatar
 
Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model.

Join Date: Mar 2007
Location: Former Middlesex
Posts: 20,265
Thanks: 1,587
Thanked 3,749 Times in 3,181 Posts
Default

Quote:
Originally Posted by biffa75 View Post
I've tried the throttle reset procedure and it doesn't appear to have worked.
According to RAVE it's only the MEMS engine management fitted to the 1.8 engine which requires the closed throttle position to be set either by using T4 or by moving the pedal between fully open and closed within ten seconds then waiting twenty seconds without touching anything before switching off the ignition.

RAVE says that the Siemens engine management fitted to the KV6 automatically learns the closed throttle position. It does not give a manual procedure. It's therefore likely that any throttle movement would not affect the ECM but simply clean the carbon track, if you're lucky!

The TPS is indeed a simple potentiometer as Colvert mentioned. I agree that renewing this is a better bet than the IAVC overhaul kit which I have tried with no improvement.

Simon
__________________
"Whatever is rightly done, however humble, is noble."
Sir Henry Royce.
SD1too is offline   Reply With Quote
Old 20th January 2021, 15:45   #8
sworks
Been absent for a while…
 
sworks's Avatar
 
Rover 75 Tourer, Classic mini Cooper S, Abarth 595 competizione, MG TF and a Hyundai Tucson PHEV

Join Date: Feb 2007
Location: Cumbria
Posts: 13,057
Thanks: 1,033
Thanked 1,686 Times in 1,040 Posts
Default

Quote:
Originally Posted by biffa75 View Post
I have noticed though that when the revs are all over the place when it should be a steady idle, if I put my foot behind the throttle pedal and pull the throttle pedal up the idle returns to normal and is okay until the throttle is used again.
Thanks
Rob
Is there any free play in the cable at the throttle body?
__________________
.................................................

'Marmite' Possibly one of the most famous 75 tourers produced! left the production line as the last of only Three Rover 75 tourers produced in Trophy Yellow. 48 hours later Longbridge closed. The last sold ordered 75 Tourer. Paid for by the Phoenix Four and handed over by John Towers to the Warwickshire Northampton Air ambulance service as a Rapid Response vehicle
sworks is offline   Reply With Quote
Old 20th January 2021, 16:44   #9
biffa75
Trader
 
biffa75's Avatar
 
Mk1 2004 tourer cdti + MK1 2003 Saloon CDT

Join Date: Nov 2015
Location: west yorkshire
Posts: 481
Thanks: 106
Thanked 91 Times in 57 Posts
Default

Thanks for all the valuable information. I'm glad the car learns the throttle position itself. One less thing to worry about hopefully.

I have no slack in the throttle cable at the throttle body end. Prior to removing the upper inlet manifold etc I don't recall there being slack in the cable then either. But the issue wasn't present then before starting work on the thermostat.

I'm going to try and pull the throttle cable out of the housing it sits in at the tb end and see if I can rotate the square block slightly.

What's making me also wonder if it's the TPS is the fact that there was a small amount of oil in the tb and when I had removed the upper inlet manifold I'm wondering if some of the oil has made its way inside the TPS..

Rob
__________________
"A Rover doesn't breakdown.... It merely fails to proceed"
biffa75 is offline   Reply With Quote
Old 23rd January 2021, 11:49   #10
Briodyjl01
Gets stuck in
 
Rover 75 Tourer, Rover 75 Saloon

Join Date: May 2018
Location: Castleford
Posts: 959
Thanks: 237
Thanked 185 Times in 113 Posts
Default

For a 2.0 v6 auto what is the normal idle ?
__________________
Too many Rovers to count ……
Briodyjl01 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 22:06.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright © 2006-2023, The Rover 75 & MG ZT Owners Club Ltd