Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Fuel vapour emissions container V8 engine

Sorry been out all day with grandkids, it’s always a good thing to clean the IACV but one thing we spent ages teaching at Volvo was chase the cause not the effect. These systems are super reliable normally and we don’t help them as they hate lack of use so un-gumming things is really important.

Teaching you to suck eggs now but change one thing and test, slow and steady and you will sort it.

BR
Colin

Hi Bruce,
To be honest I have not located the actual speed sensor, I think it comes off the VDU speedo, but I'm not at all sure. Can you give me a clue as to where i may find it please?
Thanks
Martin

Hi Colin,
Yes, very good advice, but to be honest I have been changing things slowly, but as with all intermitant faults, they are hard to find and hard to be sure you have cured the fault. What I have noticed is that each time I repair / replace an item there appears to be a significant improvement in how the engine runs, so I think I am getting there slowly. I'll clean the Idle control valve as suggested as I haven't cleaned it in 5k miles, and as its run perfectly for two years that may indeed be the problem.
Thanks
Martin

Martin, on my +8 if you follow the speedo cable it will go through the firewall and bend round into the tunnel gap at the top of the transmission where the clutch slave cylinder is. The Road Speed Sensor (a small box) is attached there to the tunnel wall, not easily accessible.

Thanks Bruce, I don't think I have a traditional speedo cable from the gearbox, as mine is an early injection model, but I'll still have a good look to see if I can figure it out.

Bruce,
I found the gearbox sender unit, it has a yellow and green wires coming from it. So ill trace it through to the ECU and speedo one day.

Martin,

Jolly good, make sure it is well earthed that was the issue with mine.

Hi Guys,

For your general information, I checked the actual operation of the purge valve, and mine cuts in after the engine has reached a certain operating temp, (not sure the exact temp as I didn't check it, but soon after the engine has run a little bit).

The Purge valve then operates continuously "pulsing" irrespective of the RPM. In otherwords it opens and closes on and off continuously, just sucking tiny amounts of vapours from the carbon canister, but only when the engine is actually running. It does not operate when the engine is stopped, even with the ignition on, although the positive is live with the engine ignition on.

I guess this works well, as it will never have any sudden drop in vacuum, causing further idle control issues.
Hope this info helps someone in the future.

Best wishes to all and thanks for all your help as always.

Martin
1997 +8 4.6ltr
MX5 ND
Touareg