Throttle pot percentage

[STE VR]

Hi all,

Have been checking engine set up lately and found that both throttle pots only read to 86.7%. I think from what I have read they should be approx 94%.

Disconnected throttle cable and the throttle bodies manually moved do get to the desired 94%. It seems the travel of the throttle cable is the limiting factor. Pedal restrictor bolt removed so getting full travel on pedal. Installed new cable and still the same. Also adjusted cable clevis so it just starts to lift throttle bodies off the idle screw (so full tension).

Any ideas?

Thanks (2003 T350 3.6)

[nawarne]

With the engine warmed up and idling, what do you get for the throttle pot %'ge opening?

Guess you know that it should be about 15% at idle?


Might be worthwhile pressing the throttle "reset" tab - providing engine is running/idling smoothly, and then seeing what you get for wide open throttle percentage? (Might also be worthwhile hitting the reset adaptives tab too).


Nick

[Basil Brush]

You can alter the length of the push rod on the back of the throttle pedal to change the starting position of the pedal and therefore the stroke.Also there are a couple of holes on the back of the pedal for the ball that connects to the push rod so you can also alter the cable to pedal ratio.

[Englishman]

I had this when I replaced a throttle cable. Seems the outer sleeve on some cables is a bit too long. Got a replacement from TVR Parts that fixed the problem. They are well aware of the issue on some cars!

[STE VR]

Hi gents,

Some great thoughts there. Will go away and have a look and see where the answer lies. TB’s sent away to Andy just for refurb/clean up so will test the above suggestions on their return.

Will keep thread updated with answers.

Much appreciated.

[STE VR]

Throttle bodies now back on and set up lovely. With ignition on/engine off throttle pots at approx 12.x%. Throttle pots only get to 90%. Do I have to have engine running and then full throttle to see the correct %? With engine idling they are both 15.5% and very linear throughout travel. Just wondering if the missing 3% with ignition off is translated to an additional 3% when running.

The above probably doesn’t make any sense but just curious before I try some of the suggestions previously posted.

Thanks

[STE VR]

Can anybody help with the above post? Just got back in garage and would like to resolve this. Only problem is I don’t really want to WOT the engine from cold to find out

[PetrolHeadPete]

For sure there is always a step between not running and running. I haven't figured out why or what it means. I have a feeling that the mbe is doing something creative with the throttle pot % and is actually the source of quite a few of its oddities in relation to consistency of running each time you start (seem to get a slightly different effect from start to start)

I noticed the other day, that even if you have a failed start attempt, the indicated % remains "as though its running" proving that its not some odd GND offset when the engine is running; its the mbe having shifted the reading for whatever reason.

[STE VR]

Thanks Pete.

Hmmm, going to have to investigate this a little further. Curiosity getting the better of me now.

I wonder why this was programmed as such and does this correspond to what I’m seeing

[STE VR]

Just to close the result of the thread.

It ended up being the throttle cable. Another new one but this time from Powers. Difficult to explain but it wasn’t the length of the outer sheath and fixings but the travel of the inner wire. The one from Powers could be pulled an extra 10mm compared to the other 2 I had. This gave me the extra I needed and now all sorted. I now have to use the throttle stop on the pedal box to restrict travelling too far.

Regarding the throttle readings with ignition on but engine off, the readings I see of 12.3% are irrelevant for this.

Might help somebody in the future.