Low Speed Lumpy Running

[PeterC]

Since buying the S3 some 15 months ago, I have slowly been working through the car making sure everything works as it should and making improvements.

I have over this period done the following:
Tappets
Replaced throttle springs
Cleaned Idle Control Valve
Cleaned Air Flow Meters & Air Filter
Replaced Throttle Pot (with good s/h unit)

and last weekend, which did improve things noticeably
Replaced Distributor Cap, Rotor & Plug Leads

All now seems to be working as it should and confirmed by Gunson tester.

The problem that I have is when driving at low speeds (boring but necessary in built up areas)I have to drive in third to sustain 30 mph and 4th to do 40 mph. The lower gears mean that the engine is running at around 2000 rpm

If I attempt to drive at low speeds in top, the car will very quickly start to judder and would I believe eventually kangaroo to a halt.

Is this usual for the 2.9i Ford motor, am I expecting too much? Surely a big V6 should remain tractable down to quite low revs. Comments anyone?

Johno - now that you have had your engine tuned on a rolling road, how does your car compare? Can you sustain 30 mph in top and accelerate away OK?

[Pete_W]

Mine will sit at 30 in 4th without these problems, pulls about 1500 rpm I think.....might well do it in 5th! Engine's covered 90k so maybe slightly more run-in

[johno]

Peter,

There are several things that may contribute to this as you are well aware...

I would certainly get the Pot checked as they are the centre of all evil in the universe of the S.

Since you have cleaned/replaced and maintained all the various ignition/fuelling sensors then I would recommend taking it to someone possibly with a rolling road and getting them to run through the sensors diagnostically whilst under road conditions to see why it isn't running.

Mine will now (again) sit at 30mph in 5th and pull away. None of them like it immensely but it is not lumpy in th slightest (when I had the latest engine problem I was sometimes having to hold 2nd !!)

These problems though are often a combination of problems. My last ones were mixture too weak, timing just off and throttle pot mis reading (again f**king things !!). None of which had been resolved by a full service and Fault Code reader and engine set up in the workshop. This was all only found during rolling road session.

Yours may be a lot simpler and my problems were more severe, but after all I have found that you are better off giving it to the experts when it comes to engine sensors. I hate to admit defeat and resent paying out money but when it comes back singing like mine you have to admit defeat and cough up !!

Cheers

Mark

[HarryW]

Johno

I would have thought to have got all of the niggles out of your car was not admitting defeat, more of a result still interested in the rolling treatment, if you could pass on the details of your experience at tower view, email off line if nescessary, I'm very keen to ensure that the toy is running at its optimum

Harry

[bills1]

I just had mine sorted at Colin Blowers.
Firstly a new set of HT leads and cap as you have already have done, then richen the mixture which was weak and causing it to 'hunt ' at lower revs being too weak.
This sounds like yours.

Cheers Peter, are you going to the Air Show at RAF Waddington with the Eat Mids Group.

Bill

[ssbell]

This describes the problem I am experiencing - just deleted my post on " HT Leads for S2" - if anyone read it (Johno did - thanks for the advice).

Despite the new HT Leads, my S2 is still doing it and hunts at tick over. It is intersting that this is a common problem. The message seems to be start with a new TP and work from there. The mixture seems the next most logical thing, if you can work out how to do it?

Does anyone have any advice on adjusting the mixture? It occurs to me that if you do not know what you're doing you could make matters worse.

Beyond that, it must all be down to tuning and tappets gaps, which surely is best done by an expert. It's a shame to have to shell out all the time, but where else do you get this much fun every day?

[PeterC]

Johno
I concur with your thoughts - that it is a combination of small errors and problems, not simply one problem. I think that cars of this age can suffer from a multitude of small ills that appear over time and are not in themselves immediately obvious.

One interesting comment made by the mechanic during the last MOT some two months ago. His exact words to me over the telephone were "the cars passed OK, the only fault was that the car appears to be running a little weak on idle when doing the emissions test, when I pressesd the throttle she was fine".

Q. Can one tweak the mixture settings by adjusting the small screw on the air meter without having access to electronic testing? How should one go about this or have I reached the point where a novice mecahnic must give way to a professional.

Don't get me wrong , the cost is not the issue here. But I do have a problem paying anyone to do something that I can easily do myself (and enjoy doing)