Cerbera 4.2 Throttle Pot

[Hoover33]

recently having fitted one of these, I can confirm that the car runs a lot smoother, however IMHO it seems not as responsive......

Is this just me, how have you others faired ??????

[KentishS2]

Perhaps slightly more progressive than the S TP where it used to be on/off on the throttle but I thought it was because i had got used to my knackered S TP?

[sotonS2]

Mine was absolutely fine after I fitted it. I think, like KS2, I had become used to it running rough so the new TP proved an instant and very noticeable improvement.

Fired up the S this morning though, and she's running OK at tickover, but she tries to die when the throttle is pressed lightly. Its almost like she's flooding.

So its off to Halfwits now for a can of carb cleaner and fiddle with the air intakey valve sensor jobbie.

[chrischat]

Fitted Cerb T/P two months ago and it cured all the problems,erratic tickover, poor starting, cutting out when slowing down.A quick fix for half the price of Ford part.

[wonderland]

Fitted one last week after the usual running problems started. Wasn't that noticable until a full can of WD40 and a load of carb cleaner - now it's back to near perfection.
Mine also starts to die from take off if it's very cold, have to give it a few revs to counter the problem... any ideas what this could be?

[adrian@]

I posted this on under the poor running ......
Here is my thought's on TP's and fitting .....by NOW 25 Oct 04 most 2.9's will of had at least one TP change and here is the thought .....Ford/TVR originally fitted tinned (SILVER) connections to this unit and the current Ford and TVR units are fitted with GOLD connections and to fit one of these there is a wiring mod that if not done sets the idle signal at 100% throttle open instead of 0% throttle open at idle.....if you have silver connections on your throttle pot then when changing to the gold unit you have to do the wiring mod.
Adrian

Even wired incorrectly at half throttle gold TP'sare giving the correct signal and the car can feel better than before but you get the problems discribed !

[Hoover33]

Wonders what this wiring mod is

[KentishS2]

adrian@ said:

I posted this on under the poor running ...... Here is my thought's on TP's and fitting .....by NOW 25 Oct 04 most 2.9's will of had at least one TP change and here is the thought .....Ford/TVR originally fitted tinned (SILVER) connections to this unit and the current Ford and TVR units are fitted with GOLD connections and to fit one of these there is a wiring mod that if not done sets the idle signal at 100% throttle open instead of 0% throttle open at idle.....if you have silver connections on your throttle pot then when changing to the gold unit you have to do the wiring mod. Adrian Even wired incorrectly at half throttle gold TP'sare giving the correct signal and the car can feel better than before but you get the problems discribed !

Thanks for that info Adrian, if I'm following you correctly on this one all of us who have changed to the Cerbera 4.2 type TP with GOLD connections will have two connections to the engine management that are incorrect and this is fooling the ECU into thinking we have a larger throttle depression than our actual throttle depression, thus some of us are also getting other problems such as flat spots as we pull away especially from cold and possibly idling irregularities.

Mine seems OK but I have changed all the other bits as well including the lower air flow meter, so everything should be fault free. The trouble is a few of the sensors on the car can give similar faults making diagnosis difficult and it seems that it isn't easy to reliably test a TP.

Are you able to post us some details about the wiring mod that you mention, I'm assuming this is just a case of changing the connector on the loom that plugs into the TP and swapping around one or two of the wires to different positions?

If we are going this far, I think there is a connector for the TP with matching GOLD pins which will give an even longer and more reliable service life. No idea what the part number is though, anyone?

I think we have all assumed that the functionality of the Cerbie TP is the same as the S TP.

>> Edited by KentishS2 on Tuesday 26th October 08:58

[Roy C]

KentishS2 said:

If we are going this far, I think there is a connector for the TP with matching GOLD pins which will give an even longer and more reliable service life. No idea what the part number is though, anyone?

Throttle Potentiometer - Motorcraft 6854780

Throttle Potentiometer Wiring Assembly - Motorcraft 5028499 (gold gonnectors).

The replacement assembly comes with wiring instructions. I seem to remember (long time ago) that two wires are transposed.

[KentishS2]

Roy C said:

KentishS2 said: If we are going this far, I think there is a connector for the TP with matching GOLD pins which will give an even longer and more reliable service life. No idea what the part number is though, anyone? Throttle Potentiometer - Motorcraft 6854780 Throttle Potentiometer Wiring Assembly - Motorcraft 5028499 (gold gonnectors). The replacement assembly comes with wiring instructions. I seem to remember (long time ago) that two wires are transposed.

Many thanks Roy, I'll order a new wiring assembly from my local Ford dealer.

[Colin Blues2]

This thread describes how the new loom should be connected up.

www.pistonheads.com/gassing/topic.asp?t=8163&f=11&h=0&hw=throttle+pot+wiring

Colin

[KentishS2]

So, for those who don't want to trawl throught the thread...

Looks like you swap the two outside connections around when you install the new plug with the gold connectors.

I've just ordered one and it wasn't in stock but will after 4:30pm, I'm impressed with my local Ford main dealer!

Mine appears to run fine but it could just be that it runs "OK" thinking that it's at half throttle all the time. It's not much extra work and not expensive (I hope), so I may as well replace it!

[chris_chim]

If the outer wiring on the pot is the wrong way around then the car will be very unhappy. If it runs ok then I suspect the fault lies elsewhere.
The only other potential issue is if one pot is linear and the other logarithmic. As far as I am aware all are linear so this shouldn't be an issue.
Certainly the wiring on my S3 was correct for the cerb pot to be a direct replacement (but then mine didn't have a ford logo, was blue so seems to be different again to all those cerb pots recently sold).

[adrian@]

.....If the outer wiring on the pot is the wrong way around then the car will be very unhappy. .....This is not the case (in my expeirence..toooooo many to mention) when being driven the throttle pot is near to being in the right place and give real information rather than a pot that is Knacker and no/poor information IF all the other parts are working correctly they seem to cope with the wrong infomation and the after several days/ weeks depending on usage does a fault re-appear
Thanks for the wiring link ( I knew someone would find it)
Adrian



>> Edited by adrian@ on Tuesday 26th October 22:03

[Hoover33]

Totally lost now !!!!!!!!!!

Let us know the results KentishS2,

.... its so much better letting someone do the experimenting

Ohhhh and welcome back

[chris_chim]

Doesn't reversing the outer wiring mean that the volts to the ecu (middle pin on pot) goes completely the wrong way around? i.e. full throttle voltage when throttle really closed and closed throttle voltage when throttle fully open.

When I reversed mine (as I thought this may be a problem) the car wouldn't rev at all and idle was all over the place so I changed it straight back. The outer wiring on mine had clearly been modified (wires cut/re-soldered in the loom close to the pot), I assume when the pot was first changed or as a factory bodge. As mentioned previously I would be a little surprised if there were any 2.9 S's that haven't had this mod already if required.

>> Edited by chris_chim on Wednesday 27th October 07:42

[adrian@]

As you say this is what should happen .....I am still finding 2.9's that are on the original PT and only last week a factory passed phone call from a dealer with the same problem, (it was the car's 3rd visit for it's 3rd PT which kept on being "cured" and being blamed on very poor quality PT's, which had never had the wiring changed) I am lucky to have a tuning workshop next door to me that I pass this sort of work to and that have all the lastest gismo's. This is after all a Ford ....all the parts are good for 200 THOUSAND miles !!...
Adrian

[Roy C]

I've found that all the TPs (including gold connector and wiring since '98) on my S2 last about 2-3 years. I've always thought this is due to them being alternately cooked (poor underbonnet ventilation) and soaked (almost directly below the bonnet vent), so it's a TVR problem rather than a Ford one.

[KentishS2]

chris_chim said:

Doesn't reversing the outer wiring mean that the volts to the ecu (middle pin on pot) goes completely the wrong way around? i.e. full throttle voltage when throttle really closed and closed throttle voltage when throttle fully open. When I reversed mine (as I thought this may be a problem) the car wouldn't rev at all and idle was all over the place so I changed it straight back. The outer wiring on mine had clearly been modified (wires cut/re-soldered in the loom close to the pot), I assume when the pot was first changed or as a factory bodge. As mentioned previously I would be a little surprised if there were any 2.9 S's that haven't had this mod already if required. >> Edited by chris_chim on Wednesday 27th October 07:42

Hi Chris,

I think you've provided your own answer there

So, if your car is fitted with a Motorcraft 6854780 (Cerbie 4.2 TP) it will have already had the mod to the wiring, so it won't be necessary to change anything.

Should you have a different part number to this on the existing TP, then it is likely that it is the original 2.9 TP and you should congratulate yourself and your TP for having enjoyed such a long and fulfilling life together.

Basically, we all now know it is best to run a Cerbera 4.2 TP as they seem to last so much longer but if you do change it and the car doesn't run, or runs like a pig then it is most likely that you'll need to swap the two outer connections around.

However, I changed my TP and it did have a different part number to the Cerbera 4.2 type I replaced it with but I didn't change my wiring and the car runs OK, can't explain that really, also my wiring looked unmolested and the connector had original tinned (silver) contacts So what TP did I have fitted previously?

Anyway, I'll have a look at the old one tonight and post the number here. I'll also look at the new one and advise the part number for the new TP which should be for a Cerbera 4.2 as that is what I asked for when ordering.

When I get around to collecting and fitting my wiring kit with the GOLD connectors, I'll solder on some breakable connectors so that they can easily be swapped around. Bearing in mind that I must seal them to ensure long time reliability.

[KentishS2]

Hoover33 said:

Totally lost now !!!!!!!!!! Let us know the results KentishS2, .... its so much better letting someone do the experimenting Ohhhh and welcome back

Hi Steve and thanks, it's nice to be back

Good idea that mate, let someone else do the legwork