stttttuttttering

[shnozz]

My car appears to be "stuttering" whilst cruising along (ie not on acceleration or lift off but just when keeping a continuous speed)

any ideas? famous throttle pot?

need to get her to Pistonfest this w'end.....

[lordb]

could be grunge in the fuel filter?

[andyf007]

Misfire on the HT Leads?

[shnozz]

lordb said:

could be grunge in the fuel filter?

is it easy enough to clean the filter? Is this covered by the bible?

[shnozz]

andyf007 said:

Misfire on the HT Leads?

how could I check for that?


Many thanks for your help so far chaps

[dern]

shnozz said:

how could I check for that?

If you can get the car in a dark garage you may be able to see the spark jumping from the lead if the leads have broken down badly. If the leads feel stiff then they're probably knackered. New leads will feel very flexible.

Has it had the same plugs in for a while? These might be breaking down a bit which would result in a kind of light misfire from my experience. You also want to check inside the dizzy cap for wear on the cap itself and the rotor arm. If you haven't changed all this stuff recently it may be worth doing anyway just to eliminate these causes and save any future breakdowns.

I didn't do the fuel filter on my S but normally they are just a dicardable item and not cleanable (some are I guess). You'll get the part number from one of the parts lists kicking about (do a search). To change it you want to remove the fuel pump relay and then crank the engine. This takes the pressure out of the system. You can the remove the pipes from the fuel filter and change it. You'll still get fuel from the pipes though so have something ready to catch it.

Good luck,

Mark

[Le TVR]

If the acceleration is ok then I'd go with the throttle pot.

[shnozz]

Le TVR said:

If the acceleration is ok then I'd go with the throttle pot.

what makes you suggest that?

Mark - most helpful, cheers mate

[dern]

shnozz said:

Le TVR said: If the acceleration is ok then I'd go with the throttle pot. what makes you suggest that? Mark - most helpful, cheers mate

Any time.

Given that the throttle pot tells the ECU how far the throttle is open and therefore what part of the map it should using and how to fuel the engine then I'd suggest that if it accelerates cleanly and responds to accelerator position changes well and you only notice the misfire at a constant speed then I'd have thought the throttle pot would be the last thing it would be. I've never had one go but the symptoms should be quite dramatic. You could try cleaning the throttle pot I guess (the procedure is, I believe, in the bible) but I'd be surprised if it is that. You've probably got the misfire more or less constantly but these things are more noticeable at a steady speed.

All imo though, of course

Mark

[Le TVR]

Clogged fuel filters, low fuel pressure, dirty pump relay contacts, duff HT leads and dizzy etc do not usually result in normal clean acceleration.

Throttle pots often wear the track out in the position that relates to 'normal cruise'.

If the throttle pot is just dirty then the contact will be intermittent at any setting and the symptom is quite dramatic by comparison.

[rhodri_harris]

Hi Shnozz

I've had 3 throttle pots fail on the S when I had it, and 2 of them gave the symptoms you describe before failing totally (with the afformentioned 'interesting' driving characteristics :-). I'd check it by unplugging it and having a drive, if it is smoother (possibly not as powerful though) then it might be worth changing it. I always carried a spare 'just in case' anyway. The other things I found on mine causing this were HT (check for arcing and tracing - carbon deposits) and vacuum leaks in the brake servo hose and rocker purge hose. These could theoretically give you good acceleration (rich mixture) but lumpy cruise due to the leak leaning the engine off.

Hope that helps

Rod

[shnozz]

hmmm - will try unplugging the throttle pot and see if i get the same problem on the way home.

I have read before about the possibility of using the SP6 throttle pot rather than the Ford Part. Has anyone any experience of this and does it require any alteration to work ok?

[HarryW]

I must say shnozz as the months have gone on your post are becoming more technical in their nature . Coming from a previous tech numpty its good to see you're getting fully involved in TVR ownership, needs must I suppose .

Harry

btw good luck with the fault and post the result as I'm sure someone else will use the information soon .

[rhodri_harris]

Any joy mate?

Let me know if you want a hand

Cheers

Rod

[shnozz]

Hi Rod - been rushed off my feet and havent managed to investigate further. I have a long run in the car tonight and will see if the problem is still apparent then. If so i will disconnect the throttle pot and see if there is any difference. Once I am back from Pistonfest and moved into the new house i have a list of things to do on the S....

new rotor arm
new HT leads
new plugs
new throttle pot
re-align window frame
rub down/waxoyle chassis
check gearbox oil
check diff oil and try and locate minor leak.

aaaaaaaaaaaargh

or i may just put her up for sale and go buy a Griff/Chim

[shnozz]

BTW - how is your Griff 500 going? I have moved from Waterside Park now but walked around for a look before I left. I must say she is gorgeous really stunning mate.

[rhodri_harris]

Going like a charm mate, had a couple of teething problems, but all fine now. Think it needs a louder exhaust though, miss the raw edge of my S

Need to phone the new owner actually, and make sure all is well, anyone on here bought it?

[Psychobert]

shnozz said:

Hi Rod - been rushed off my feet and havent managed to investigate further. I have a long run in the car tonight and will see if the problem is still apparent then. If so i will disconnect the throttle pot and see if there is any difference. Once I am back from Pistonfest and moved into the new house i have a list of things to do on the S.... new rotor arm new HT leads new plugs new throttle pot re-align window frame rub down/waxoyle chassis check gearbox oil check diff oil and try and locate minor leak. aaaaaaaaaaaargh or i may just put her up for sale and go buy a Griff/Chim

1st few of those would take 10 minutes at PF if you've the new bits to hand, also a good place to cock-up as there are bound to be a few around that know what they are doing and could help

Usually have a few tools in the boot if I'm going more than a few miles, (you never know..) Can give you a hand at PF if you like..

[shnozz]

Rod - glad to hear it mate - it really does look lovely. I have seen hundreds of Griffs before and confess i am not a great lover of dark greens on cars - but in the fibreglass yours looked simply gorgeous. Really made me start thinking

Psychobert - not a bad idea that. Could fit it in whilst having a few jars on saturday afternoon. Now where would I go to buy the parts? Anyone? Do Motorcraft have outlets?

[rhodri_harris]

Try the 'Ford' garage in Chandlers Ford mate. I used to get all my stuff there, and if it isn't in stock they can usually get it next day