Kv6 2.5 1999 model Cold start problem - Page 4

paul hindmarsh · 4th January 2010, 20:50

I've started the car from cold and ran it happily 3 times now but tonight it's back to square 1. Removed the IACV and it's closed.
So it seems the stepper motor is only moving the valve into the closed position but not opening it on start up. Knackered stepper motor ?
However it must be working ok when warm because with the throttle in the closed position and I select D on me auto box the revs increase slightly then settle to normal . IACV working ?
Iv'e had a call from my garage today .They have had a response from XPart and they suggest replacing the MAP sensor which incorporates an Air Temperature sensor.

paul hindmarsh · 4th January 2010, 22:21

Quote:

Originally Posted by paul hindmarsh

I've started the car from cold and ran it happily 3 times now but tonight it's back to square 1. Removed the IACV and it's closed.
So it seems the stepper motor is only moving the valve into the closed position but not opening it on start up. Knackered stepper motor ?
However it must be working ok when warm because with the throttle in the closed position and I select D on me auto box the revs increase slightly then settle to normal . IACV working ?
Iv'e had a call from my garage today .They have had a response from XPart and they suggest replacing the MAP sensor which incorporates an Air Temperature sensor.

From what I've read on the internet the MAP sensor and Air Temperature sensor have more to do with the fueling side of things and don't directly involve the IACV. Is this correct ?
Again from information gathered from the internet ,with the stepper motor removed but connected to the cars loom ,switching the ignition on should make the plunger at the end move in and out.
Is this correct ?
Mine doesn't move until the ignition is switched off ,then it only moves out or towards the closed position.

paul hindmarsh · 9th February 2010, 14:29

At long last I have found the cause of my problem. A faulty coil in the IACV.
Replaced the IACV with a known working one and no more cold start problem.

BigRuss · 9th February 2010, 15:28

IIRC the idle control valve is made by Magnetti/Morrelli quite a few cars use the same type as those fitted to our cars, the main difference is the length and shape of the tip.

I had a problem with a Citroen recently where the whole throttle body had been replaced by another mechanic with one from another slightly newer car. This had got rid of the original low power and mis-firing faults but it stalled often when pulling up at junctions and traffic lights etc.

The shape of the tip was different on the newer part and restricted the air in the throttle body at idle, correct new one fitted and fault disappeared.

Anyway, I wonder if the tips are removeable if they are and the stroke of the shaft is the same then it's possible that others could be modified to provide a cheaper source of parts. Will go and see if I can get the tip off that old Citroen one then compare the stroke with one on the V6.

Good to se you got yours sorted.

9th February 2010, 15:28	#34
BigRuss Premium Trader 75 CDT Tourer,2.5 Launch Saloon, Omipro MG/Rover (T4) Join Date: Jul 2007 Location: Liversedge, West Yorkshire Posts: 5,414 Thanks: 1,105 Thanked 1,340 Times in 661 Posts	IIRC the idle control valve is made by Magnetti/Morrelli quite a few cars use the same type as those fitted to our cars, the main difference is the length and shape of the tip. I had a problem with a Citroen recently where the whole throttle body had been replaced by another mechanic with one from another slightly newer car. This had got rid of the original low power and mis-firing faults but it stalled often when pulling up at junctions and traffic lights etc. The shape of the tip was different on the newer part and restricted the air in the throttle body at idle, correct new one fitted and fault disappeared. Anyway, I wonder if the tips are removeable if they are and the stroke of the shaft is the same then it's possible that others could be modified to provide a cheaper source of parts. Will go and see if I can get the tip off that old Citroen one then compare the stroke with one on the V6. Good to se you got yours sorted. __________________ Replacement Key Service http://https://the75andztclub.co.uk/...d.php?t=244732 Full T4 Testbook diagnostics available. Diesel ECU repair and replacement. Options enabled or disabled as required. Diesel X-Power 135 and 160bhp, Rover 1.8T 150 to 160 MG 160 V6 to 177 upgrades available P.M. for details.

4th January 2010, 20:50	#31
paul hindmarsh Newbie Rover 75 2.5 V6 1999 V reg Join Date: Jun 2009 Location: Lynemouth ,Northumberland Posts: 20 Thanks: 0 Thanked 0 Times in 0 Posts	I've started the car from cold and ran it happily 3 times now but tonight it's back to square 1. Removed the IACV and it's closed. So it seems the stepper motor is only moving the valve into the closed position but not opening it on start up. Knackered stepper motor ? However it must be working ok when warm because with the throttle in the closed position and I select D on me auto box the revs increase slightly then settle to normal . IACV working ? Iv'e had a call from my garage today .They have had a response from XPart and they suggest replacing the MAP sensor which incorporates an Air Temperature sensor.

9th February 2010, 14:29	#33
paul hindmarsh Newbie Rover 75 2.5 V6 1999 V reg Join Date: Jun 2009 Location: Lynemouth ,Northumberland Posts: 20 Thanks: 0 Thanked 0 Times in 0 Posts	At long last I have found the cause of my problem. A faulty coil in the IACV. Replaced the IACV with a known working one and no more cold start problem.