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?

[sideways danny]

change the thermostat. Clean the throttle body. Clean and lubricate (second part is important) the idle control valve

[16v_russ]

Next on the list to do Danny - Stat was changed along with coolant before it came off the road for a year, so I am assuming that should still be ok - it was more me wondering if I had earthed the right wire, due to the difference in symptoms when unplugging the cable wiring pulg, compared to plugging it back in - ie the idle and reving although not right, was better with cable plugged in, but im really just speculating, il give the mentioned a good clean up and report back

[16v_russ]

Update time,


Had about 2 hours on Duf today, I took the ICV off and gave it a good clean with carb cleaner, followed by some WD40, I cleaned every electrical plug I could find with electrical cleaner, I re-earthed the dash again (Made a better job of it) and took the air filter off and cleaned the throttle body (Well I say clean, it was spotless to begin with).

I put it all back together, jump started it as the battery was flat (Not used it all week and I think the battery needs a charge so il chuck it on the battery charger at work tomorrow) and took it for a tentitve first drive.


Bottom line is, it was better than before, but still not fixed.

Was pretty gutted to be honest, I was hoping it would fix it, but I thought of one thing I didn't try - looking at the idle screw on the throttle body.

So I had a look, and the white cap was down the side of the screw, which was a big relief - it's not great it had been fiddled with, but at least I knew it wasn't as it was supposed to be. So while it was running, I screwed it in - I was screwed out LOADS! As I kept turning, the idle got lower (As expected) and I took it to about 1000 rpm - I went for another drive and it was so much better - revs dropping much faster, and every time I stopped the idle dropped to circa 1000rpm.

Now it's not perfect - the revs still go up slightly when I dip the clutch, and the revs don't drop to idle as quick as id like, but it is not correctly mapped so that may be something to do with it and it is now 95% better and much much more enjoyable to drive :)



Just a few questions:

Should the ICV 'tap' if you tap it? When it was off, I noticed if I shook it, there was like a tap or rattle from inside the IVC - if I tapped it lightly on my carpet in my garage it tapped - as if something was loose/worn inside it - does anyone know if they are supposed to?

Secondly, the revs drop sometimes when you are on idle and turning - does the Williams have a rev stabalising valve in the power steering pipes or pump?

Cheers guys and thanks for all the advise so far :)

[16v_russ]

Anyone?

[Coops]

theres a pressure relief valve in the rack i believe that could cause the idle fluctuations on cornering

and yes the ISCV will rattle, the position of it is held constantly by a suppose a magnet or something, so with no power to it the shutter is free to flap about, the looser it is the better, its the build up of soot and crap over the years that stops it moving freely

[16v_russ]

Cheers Coops :)

Il see what i can find out r.e. The valve, apart from a new speedo cable its the only thing i can think of that is causing the idle problem