Very odd T5R problem

**Niles** · Thursday 19th February 2009, 23:48

Not my car but a mates. T5R manual M reg. When the cars running it idles at 800rpm very smoothly. Rev it & the revs build to 6500 no problem, however, the revs take ages to drop. Sometimes it behaves, I went out in it tonight & gave it some welly, go's really well but when at 'giving it some' the revs don't fall between gear changes & when coming to a halt allowing the engine to help with slowdown (trailing throttle) the revs still stick up around 4500-5000, then sits for a second or 2 then slowly falls.
Really annoying bit is that if you pull over & rev it while the cars standing still the revs seem to behave.
Throttle body has been cleaned & linkage isn't an issue. Can't see any air leaks & as the idle is perfect an air leak isn't really a suspect.
Turbo blows nicely.
Any ideas? The owner is getting majorly tired of it.

**Taff - t5** · Friday 20th February 2009, 00:02

Have you cleaned the air idle control valve?
The revs tend to stick when its full of c--p!!

**Jod T5** · Friday 20th February 2009, 01:01

IAC valve comes to mind http://www.volvoforumsrepairs.org.uk/800Repairs/iac.htm , also the operation of the recirc valve spring....
Cheers
jod

**Niles** · Friday 20th February 2009, 11:55

Originally Posted by Taff - t5

Have you cleaned the air idle control valve?
The revs tend to stick when its full of c--p!!

not sure mate if its been cleaned. at idle the cars fine. May well be worth a good look & clean!!!

**Niles** · Friday 20th February 2009, 12:01

Originally Posted by Jod T5

IAC valve comes to mind http://www.volvoforumsrepairs.org.uk/800Repairs/iac.htm , also the operation of the recirc valve spring....
Cheers
jod

why the spring,do you think that a tired spring won't release the pressure & hold the pressure in the cylinders?

**Niles** · Friday 20th February 2009, 21:43

just been told the Idle Control Valve is spotless & squeeky clean.

Any further ideas other than the recirc valve spring? (it will be investigated)

**Saaamon** · Friday 20th February 2009, 22:54

Same problem on my 850R its very annoing, would like to find a solution.

**Dangerous Dave** · Friday 20th February 2009, 23:20

Have you checked the throttle flap (sounds noobish I know) it gets the crud from the PCV system on it, obviously this would also mean that the IAC valve should be fouled up too, but its not always the case. Its another thing to scratch off the list.

**PaulZX** · Friday 20th February 2009, 23:41

I get the same thing on my T5.... I'll be watching this thread with intrest...

**Dangerous Dave** · Friday 20th February 2009, 23:46

Also, to check the IAC valve, disconnect the multiplug, there should be three pins on the IAC. Connect a multimeter (set to resistance) to pins 1 and 2, then pins 2 and 3. The reading should be 9 to 14 ohms.

You can also check the movement of the valve by removing the assembly and twisting the body back and forth, you should be able to hear the valve moving inside. If not, then it might be stuck/sticking.

HTH

Bomb

**marky 76** · Friday 20th February 2009, 23:56

i had the same problem on my c70 and i ruled out airleaks ,,,, BUT i found the problem was indeed a airleak on the inlet manifold gasket ... sounds very much like it,s getting more air from somewhere !!!!!!!!!!!!!!

**Niles** · Saturday 21st February 2009, 00:00

Originally Posted by bomb192uk

Have you checked the throttle flap (sounds noobish I know) it gets the crud from the PCV system on it, obviously this would also mean that the IAC valve should be fouled up too, but its not always the case. Its another thing to scratch off the list.

The throttle body & flap have been cleaned. My mate who owns the car is a very VERY experienced mechanic & the problem has lost him already & doing his head in.

So, things to check are..... Recirc valve & inlet manifold gasket. Boost control solenoid???

**Dangerous Dave** · Saturday 21st February 2009, 00:05

Fair enough mate, hope he gets it sorted, seems like its affecting quite a few people.

**Tomcat** · Saturday 21st February 2009, 01:04

Sure it's not the throttle cable?, sounds like it from the syptoms. If you have a spare then why not swap it just to be sure?.

**flyingbrick** · Saturday 21st February 2009, 01:08

Ye mine has the same problem this winter. Cant remember it doing it last summer. It seems to have gone away at the moment. touch wood.....

**Saaamon** · Monday 2nd March 2009, 21:59

Originally Posted by Niles

The throttle body & flap have been cleaned. My mate who owns the car is a very VERY experienced mechanic & the problem has lost him already & doing his head in.

So, things to check are..... Recirc valve & inlet manifold gasket. Boost control solenoid???

Had anymore luck yet mate?

**roryscott30** · Monday 2nd March 2009, 22:25

I posted a message a few back and unlike you got almost no response, thanks guys. I struggled on and carried out the same checks as you. I researched the problem to the temperature sensor and got a new one from Rufe and it has cleared up. Mine was along the same lines erratic revs which can be a classic case of TS fault. New one is around £20 and in any case worth a try.
Other things to try are lambda sensor which should really throw up a code.

It's nice to get replies when you're tearing your hair out!

**callyuk** · Monday 2nd March 2009, 23:18

This is a common issue on the 850's my T5 does it as well and was told by a few people that the only real way to elimiate it was through a remap although cleaning out throttle body ect. does help

**850twr** · Monday 2nd March 2009, 23:41

i had this problem untill i fitted my forge dv and blanking plate, so the original recirc must of been at fault. made a big difference .

**Alan M** · Tuesday 3rd March 2009, 08:02

I disconnected and blanked off the pipework to and from the PTC in the Maf pipe and cured this problem. Even with new pipework and clips from Rufe mine still had a rise in revs with the throttle closed until it was cured by venting the PCV to atmosphere and blanking off the nipple on the side of the inlet manifold.