The old high idle thing - Iv tried the speedo earth......

[16v_russ]

And it hasn't worked.

Well, I best explain what it's doing, Basically the engine spec is Angelworks cams with Cat pulleys, Gunnerchip (7100 rev limit) Prowler exhaust manifold, and usual filter and exhaust change.

Idle is generally 1300-1500 rpm, it is a little lumpy (Which i put down to the cams) but it idles about that rpm.

When slowing down, when I go to change down gear, as soon as I dip the clutch the revs shoot up to 2000-2200rpm, hold there for about 3 or 4 seconds, then drop to 1300-1500rpm.

It does this every time, and also does it if I stop at a junction for example.

It also sometimes wants to run on - example is I am driving along 2nd gear in a 30, a bit of traffic so I am on and off the throttle - sometimes I let off and it slows down as you would expect, other times it sticks at circa 2000rpm as if I had not let off the throttle (it is not throttle cable sticking)

If I stop at any point in my trip, it will return to it's 1300-1500rpm idle - if I switch the engine off, then restart it, it will return right away to the high idle.

Lastly, if I drive along at normal A road/motorway speeds, if I dip the clutch the revs will shoot up to 2000-2500 rpm and stay there until I slow down to a near stop, which is when it drops to its 1300-1500rpm again.

I have re-earthed the black speedo earth, and upon start up from cold, I thought it was better as it idled at circa 1200, then dropped quickly to 1000rpm, but after a few miles driving it was back to doing the above again.

I also tried unplugging the speedo cable plug, in which made it much worse, and idle was now 3000-3500rpm. Plugging the cable plug back in returned it to 1300-1500rpm.

To be honest, I don't think the speedo cable is the issue, as if I switch the car off after driving, then start it back up the idle is still high.

The car has stood for a good year without use, so the next stage I am thinking is popping the ICV off and cleaning it fully, checking the TPS, and checking/cleaning the plugs for both.

Does anyone have any other ideas to try? Iv been away from Mk1's for a good 7 years, so although I know my way round an engine bay, id rather ask and be sure

[andyleep]

Clean ICV, maybe adjust tps. That's the start!

[16v_russ]

Oh one other thing, the black wire I re-earthed, obviously I re-earthed the cable side, but I have not earthed the other side I cut - does that little black wire earth anything else or is it just the cable? I assumed it was just for the cable, hence not earthing that other end

[Wobba]

Clean ICV, maybe adjust tps. That's the start!

First thing I would try is ISCV. Then I'd try a air leak test and a new throttle body/tps.

[16v_russ]

Cheers guys, it has had a icv at some point, but if im honest im not sure where, il start with a clean

Just to confirm, I don't need to do anything with the other half of that black wire do i?

[Coops]

pretty sure its the wiring loom side you need to earth. although if i'm totally honest its been that many years since I did mine I really can't remember.
no harm in earthing both sides tho so personally i'd try it

[16v_russ]

Cheers Coops, I did search and as far as I could tell it's the cable side that had to be earthed? I hope someone who may have done it recently might be able to confirm?

[Wobba]

Its the black wire coming from the speedo cable under the dash. Just earth it to the metal under the dash.

[16v_russ]

Im sure I have the right one, it's a very thin black wire than runs from the head of the speedo cable back into a wiring plug (with 2 other wires, a 3 pin plug attached to the cable) then corrisponding plug's 3 wires (a black, white and grey i think?) runs off under the dash.

So I have cut that very thin black one that runs from the speedo head, and earthed that to the metal bracket behind the dash unit (Obviously cleaned some paint off first)

Is that the correct wire guys?

[16v_russ]

And as said, I have earthed it on the cable head side (before the wire reaches the multi-plug) and I have not earthed the loom side (ie the side that is after the multi-plug, that runs off under the dash)

As Coops has said, I think I may try earthing both sides, see if that helps?