Sounds like the TPS isn't returning to the default closed throttle position meaning either a failing TPS or you got too enthusiastic when you adjusted the throttle cable. The Engine ECU will have a memorised voltage for the TPS at a closed throttle so if it is seeing a higher voltage it assumes you have opened the throttle slightly so opens the IACV to raise the revs. Apparently the throttle cable adjustment is pretty critical on a Thor and needs to be done by the book.

Thanks Richard.

Right I've returned it to "original" with regards to throttle cable, and it still does it..

I noticed it started right after I overtook a tractor "with the original throttle cable setting" instead of going 1/4 to 1/2 throttle like i usually do I just mashed the throttle and she rightfully took off however when turning around in my drive i noticed the idle had raised to 1100 and would just sit there, and then drop back down..

Now on cold start it sits at 1500 or 1700 and sits there until she warms up, then it starts to fluctuate and it drops suddenly to the normal idle speed.

I've replaced the TPS mainly because I was getting spurious codes "fixed"

From memory i have an Idle air control valve malfunction code, but my code reader has been borrowed by a friend!

IIRC it was PO505..

Before this issue it would fire and then cut out or it would fluctuate between 100 and 1200rpm rapidly, so i had to hold the throttle for around 30secs to allow it to stabilise.

This is my idle when cold..

The old TPS was all rattly, which i thought was odd..

Thanks all.

If you've changed the TPS you need to reset the adaptive values to store the closed throttle voltage from the new sensor which will be different to the old one.

Cheers Richard

Will a standard OBD reader be able to do it?

Nope, Nanocom, Faultmate, EASUnlock V4 and maybe Lynx. A reader is just that, a reader, it can only read not write.

Update time..

After pondering the idle issue I clouted the thing with a rubber hammer and squeezed the pipes going to the IACV the idle dropped and a "click" came from it, and the idle dropped down to normal...

Helps being a caveman I guess!!

Sounds like the IACV is gunked up then.

You can't pull the Thor ones apart - you have to just squirt cleaner into the openings and drain out all the muck that it dislodges and keep doing that until it moves freely.

Right i fitted a new 2nd hand unit and the idle is back to how it should be..

I've taken my old one apart "with a hammer" and have noted a few things.....

1 The air restrictor thingy has 2 bearings the upper most one is a needle roller bearing, mine had seized solid, due to corrosion..

Spraying contact cleaner in there might release any crap in there, but it will only sit and seep through this bearing, probably only washing out the grease in the rollers..

You'd probably be better off spraying a release agent in there instead of contact cleaner, from my observations

H

I just made a mental note to not buy "known good" P38 parts off any e-bayers based in Herefordshire : o)