Running rich & lumpy - TP ????
Discussion
I'm sure the TP issue has been covered to death on this forum but I'll post this anyway.
My S (2.9) has started running very rich (it stinks) and lumpy, particularly when cold. When warm, tickover will suddenly go from 800-900 revs upto 1500 revs and remain high until I turn the engine off, leave for a few seconds and fire it up again at which point the revs return to normal. Pulling away, the throttle has to be feathered for the first couple of seconds otherwise she coughs and dies (it seems like over fuelling). She also suffers the odd 'hiccup / kangarooing' when running at, say, 2000 revs.
I replaced the coil, leads, rotor last weekend and the plugs were new about 1000 miles ago but the problem is getting worse not better.
So, are these symptomatic of the dreaded TP ?
Can TPs be tested ? After all, its a potentiometer (variable resistor) so has anyone done resistance tests ? Any ideas what to expect Ohm wise from one extreme to the other ?
I'm kind of loathed to blow £50.00 on a new TP and find the fault lies elsewhere - although KS2's £22 Cerbera TP trial seems successful.
Thanks in advance, guys.
My S (2.9) has started running very rich (it stinks) and lumpy, particularly when cold. When warm, tickover will suddenly go from 800-900 revs upto 1500 revs and remain high until I turn the engine off, leave for a few seconds and fire it up again at which point the revs return to normal. Pulling away, the throttle has to be feathered for the first couple of seconds otherwise she coughs and dies (it seems like over fuelling). She also suffers the odd 'hiccup / kangarooing' when running at, say, 2000 revs.
I replaced the coil, leads, rotor last weekend and the plugs were new about 1000 miles ago but the problem is getting worse not better.
So, are these symptomatic of the dreaded TP ?
Can TPs be tested ? After all, its a potentiometer (variable resistor) so has anyone done resistance tests ? Any ideas what to expect Ohm wise from one extreme to the other ?
I'm kind of loathed to blow £50.00 on a new TP and find the fault lies elsewhere - although KS2's £22 Cerbera TP trial seems successful.
Thanks in advance, guys.
By all acounts the cerbie TP is a better option for replacement and is approx £23
I think "KentishS2" recently fitted one
Edit for link
http://pistonheads.com/gassing/topic.asp?t=129816&f=11&h=0
>> Edited by Pies on Wednesday 13th October 12:39
I think "KentishS2" recently fitted one
Edit for link
http://pistonheads.com/gassing/topic.asp?t=129816&f=11&h=0
>> Edited by Pies on Wednesday 13th October 12:39
Thanks Pies, its certainly an option and if the TP has gone, definitely one I'll be taking.
I was wondering though if anybody had actually tested, dismantled or rebuilt a TP.
As I understand it, it only comprises a strip of metal which slides along some brushes so it could be cleaned or refurbed if you can get inside the thing (I won't know this until I take mine out and have a prod around).
I was wondering though if anybody had actually tested, dismantled or rebuilt a TP.
As I understand it, it only comprises a strip of metal which slides along some brushes so it could be cleaned or refurbed if you can get inside the thing (I won't know this until I take mine out and have a prod around).
See this link with ref to cerb pot and dismantling throttle pots. http://pistonheads.com/gassing/topic.asp?t=113644&f=11&h=0&hw=E1586
They are pretty well sealed and completely knackered once opened so refurb is out of the question.
I used the cerb pot many years ago because a TVR dealer suggested it.
They are pretty well sealed and completely knackered once opened so refurb is out of the question.
I used the cerb pot many years ago because a TVR dealer suggested it.
chris_chim said:
See this link with ref to cerb pot and dismantling throttle pots. http://pistonheads.com/gassing/topic.asp?t=113644&f=11&h=0&hw=E1586
They are pretty well sealed and completely knackered once opened so refurb is out of the question.
I used the cerb pot many years ago because a TVR dealer suggested it.
Thanks for the tips CC. At £20 odd its probably worth replacing the S TP with a Cerb TP anyway for longer term reliability (hopefully !). Who knows, it may even solve the running problems.
It certainly did on mine (90 S3).
I think there may be some issues with very early engines where the pot slider goes the other way so you have to reverse the two outer wires on the connector but most should just bolt straight on. You know if its wrong as the car won't be at all happy...
It is certainly a direct replacement for all the various Ford TPs I went through for a Granada/Sierra 2.9 engine (including one that had an O ring seal, that was useless as well).
I think there may be some issues with very early engines where the pot slider goes the other way so you have to reverse the two outer wires on the connector but most should just bolt straight on. You know if its wrong as the car won't be at all happy...
It is certainly a direct replacement for all the various Ford TPs I went through for a Granada/Sierra 2.9 engine (including one that had an O ring seal, that was useless as well).
Top advice as always guys.
I have a copy of the Bible (it was my first purchase after getting the S) but I didn't realise the resistances were listed. I'll do some tests. Thanks for the offer of the info though Bugsy.
Editted to add: Idle sensor, eh ? That could make sense. I'm pretty confident the variable tickover is a electrical / electronic (ie sensor) issue rather than mechanical since the revs return to normal if the engine is switched off then on again.
I'll have a good poke around this weekend.
>> Edited by sotonS2 on Thursday 14th October 08:36
I have a copy of the Bible (it was my first purchase after getting the S) but I didn't realise the resistances were listed. I'll do some tests. Thanks for the offer of the info though Bugsy.
Editted to add: Idle sensor, eh ? That could make sense. I'm pretty confident the variable tickover is a electrical / electronic (ie sensor) issue rather than mechanical since the revs return to normal if the engine is switched off then on again.
I'll have a good poke around this weekend.
>> Edited by sotonS2 on Thursday 14th October 08:36
Bear in mind that the resistance of the potentiometer doesn't really matter (within reason) as the slider is just reading of a voltage between one side of the resister and the other.
All my duff potentiometers read fine on a meter so I don't believe this is any indication of their condition anyway.
Disconnecting it as mentioned earlier seems the most reliable test.
All my duff potentiometers read fine on a meter so I don't believe this is any indication of their condition anyway.
Disconnecting it as mentioned earlier seems the most reliable test.
chris_chim said:
Bear in mind that the resistance of the potentiometer doesn't really matter (within reason) as the slider is just reading of a voltage between one side of the resister and the other.
All my duff potentiometers read fine on a meter so I don't believe this is any indication of their condition anyway.
Disconnecting it as mentioned earlier seems the most reliable test.
Will bear it in mind that your duff TPs meter test OK. I just thought I might be able to detect a flat spot / dead zone with a DVM.
I'll disconnect and see what happens.
shnozz said:
Will Power said:
It's probably worth checking the loom around the TP as they are also known to be unreliable.
More unreliable than the rest of the wiring on a TVR ??
neil, if you need a loom I have one in the garage.
Cheers Phil, I don't think it will come to that but it's handy to know there's one kicking around if needs be.
I've nipped home at lunchtime and with it being sunny I'm going to take the Tiv back to the office to give the spray a go - the boss is away and I am nursing a hangover so tinkering with car is far preferable to working.
All being well, I can drop the spray to yours tonight before the H&C meet (6ish ?) and let you see the results.
Gassing Station | S Series | Top of Page | What's New | My Stuff