S2 Idle

[chingers]

Parked the car in the drive for a week over Easter and when I get back problems changing gear arising from the revs not dropping quick enough. Under normal conditions foot off throttle dip clutch and the revs drop slowly to 2000rpm hesitate then again drift down slowly to idle speed.Apart from that everything is running as normal with a good steady idle about 8-900rpm. I have checked out the other threads on idling and have done all the obvious stuff i.e. stripped cleaned and lubricated pedal, cable throttle linkage and throttle body and the throttle closes to the stop immediately you take your foot off the pedal. The idle speed control valve has been removed, split, cleaned with carb cleaner several times. A cheap replacement valve from a scrapyard cleaned and fitted but the symptoms remain.Does anyone know of anything else I should check before I part with cash down at Mr Fords for a new control valve?
Chris P.

[Gilesy]

Hi Chingers

My S2 does EXACTLY the same thing! I have also gone down the route of cleaning Idle Speed Control Valve, Throttle Butterflies etc.. I was advised by a TVR garage to change the Throttle Pot., which I did, all to no avail. The timing is about right, I have reset the ECU. What I have noticed recently is that the idle seems OK when the engine is cold but plays up as soon as you open the throttle when it is at normal operating temp.. I was thinking that maybe the mixture is all to cock ie. ECU still giving cold engine fuel for a warm engine, the exhaust also stinks of over fuelling when this is happening, so this is the route I am now going down.

I'm not sure about the Idle Speed Control Valve as you have already changed it for another and the chances of it being faulty and giving the same symptoms are small. Although that said .....................?

Let me know how you are getting on and I'll do the same, two heads better than one and all that.

Cheers
Ian

[Colin BlueS2]

Don't know if this helps.

My S2 would only idle between 1400 and 2000. Did all the usual clean the idle valve, throttles, air vanes etc but didn't seem to make any difference. For a while I disconnected the idle valve and that reduceed the idle when hot to about 900 but was a pain when cold.

I noticed that when I moved the cables associated with the throttle pot and idle valve it seemed to have an effect on the idle speed. So I re made the solder connections that I had done to connect the new gold contact loom for the throttle pot and that seems to have fixed it. Sat in traffic today for over an hour this morning and idle was steady as a rock at 900.

I can only assume that there was a poor connection and so the bad input from the throttle pot was upsetting the ECU causing it to compensate using the idle valve.

Hope it helps

Colin

[chingers]

Thanks for the input guys. I have decided to hold off paying the £62 that Mr Ford wanted for the new valve and drive it around to get a better feel for the magnitude of the problem. Unfortunately driving it around was easier said than done as I got distracted by a ruptured fuel return pipe which sent a significant amount of petrol down my driveway and what I think was a faulty cigar lighter causing the indicator fuse to blow every few minutes. These now sorted (I hope) that leaves me the weekend to get back to the throttle problem. If I come up with anything new I'll post it.
Thanks again.
Chris P.

[HomerJ]

I used to have an S2 which had similar problems with erratic idling and throttle response. My local dealer diagnosed a faulty throttle potentiometer. It was such a common problem with S's that it was the first thing the mechanic looked for, and he had a box of them in stock.

As far as I understand, the potentiometer is a variable resistor which is connected to the throttle butterfly and converts its position to a current, and sends it to the ECU so it 'knows' how much throttle you're giving it, and adjusts other settings accordingly. (That's it in layman's terms, which is as technical as I get). It's a small black plastic gizmo, about the size of a matchbox, attached to the throttle butterfly spindle with a multiplug, and held on by two little nuts, I think.

The dealer kindly replaced mine, but it was well over £50 + labour etc and that was years ago. So when it did he same thing again I had a go at cleaning it.

No problem, just undo the nuts, and slide it off - no need to disconnect the wiring. The best stuff to clean it with was a 'rubber and nylon lubricant' which I got from Halford's, but which is probably available elsewhere, all sorts of places I imagine. It was an aerosol, like WD40, which would also do the trick I would think.

The problem is that the part has a plastic on plastic rotating parts, so dirt, or lack of use can cause it to stick, sending duff messages to the ECU, and that's also why the rubber lubricant is best. If cleaning it doesn't work, then replacement is the next easiest option.

For what it's worth, my wife had a 205 GTI with Bosch LE jetronic injection, I think, which used to idle very badly. The main problem was a tiny bit of dirt on the air bypass (idle) valve, dirty butterflys (it was all 'downwind' of the crankcase breather - that was clever), but also that the spring in the airflow meter wore. Even this wasn't too difficult to fix, it was the diagnosis which was the tricky bit.

I mention this in case it's some help, deffo worth cleaning the butterflys but I'd try the potentiometer first.

Good luck.

Nick