No kickdown

[AndyH]

Hi folks, having changed the exhaust, front brake pads and alternator successfully there is only one niggle left. The gearbox won't kickdown from top gear. Whatever I do it changes into top at around 38mph, uphill, downhill or flat. This is annoying on the hills as I either have to put up with sluggish performance or manually change down to S. The hold button does nothing at all and the hold light flashes codes 11, 12 and 16. 12 is the throttle position sensor but the other codes I don't know.

What do we reckon folks, splash out on a throttle position sensor and hope? Has anyone else had this?

Yours in hope,

Andy

[Northern Bongolow]

on the top of the pump is a nut and locknut, under the metal top is a diaphragm and spring, this gets full of oil from the 10mm tube that goes to the inlet manifold elbow, carefully open it up and check its cleaned out and the 10mm pipe is connected, they snap off, and check to see if the diaphragm is in good nick not splitt of crinkly.

if thats all ok then,

on a 96 diesel its an adjustable throttle position sensor, undo the screw at the black cap with the writing on it, then try moving it along the slot, marking it first may be a good idea. this adjust when it changes all gears, have a play about.

[AndyH]

Thanks NB. I'll be getting greasy on Friday!

[AndyH]

Well I stripped that diaphragm and whilst it had a small amount of oil it looked ok. I've tried the Throttle Position Sensor at each extreme of its adjustment but it makes little difference. It will kickdown in the lower gears but it changes into overdrive at 2500 rpm (indicated 35mph) and drops to 1500 rpm where it is gutless until over 2000rpm. I wonder if it has to do with the 16inch wheels someone has fitted? All tyres are 215/60 R16. Surely the rpm at which overdrive is selected should vary with throttle position?

[mikeonb4c]

Well I stripped that diaphragm and whilst it had a small amount of oil it looked ok. I've tried the Throttle Position Sensor at each extreme of its adjustment but it makes little difference. It will kickdown in the lower gears but it changes into overdrive at 2500 rpm (indicated 35mph) and drops to 1500 rpm where it is gutless until over 2000rpm. I wonder if it has to do with the 16inch wheels someone has fitted? All tyres are 215/60 R16. Surely the rpm at which overdrive is selected should vary with throttle position?

Wheels shouldn't affect it - I swap between 15" and 17" wheels with no issues. If its not the TPS then I wonder if its related to something like the solenoid pack. He doesn''t come on here much but we have and excellent autobox specialist whose avatar name is Alacrity (real name Geoff). If you've searched old threads and found nothing that covers your symptoms you could try PMing him in case he picks it up and replies

[Northern Bongolow]

Well I stripped that diaphragm and whilst it had a small amount of oil it looked ok. I've tried the Throttle Position Sensor at each extreme of its adjustment but it makes little difference. It will kickdown in the lower gears but it changes into overdrive at 2500 rpm (indicated 35mph) and drops to 1500 rpm where it is gutless until over 2000rpm. I wonder if it has to do with the 16inch wheels someone has fitted? All tyres are 215/60 R16. Surely the rpm at which overdrive is selected should vary with throttle position?

that sounds about right to me, the turbo doesnt start to kick in till about 2200-2300 so wont take off till then, the overdrive or top gear is only for when the revs are just about off, any hill will make it jump down. it should go into top at around 30 mph though if your light footed, maybe a fuel filter or a clean of the thimble filter in the top of the injector pump will help

[AndyH]

It takes off fine if I drop it into S. It just won't kickdown automatically on a hill or if I floor it in overdrive. It must be some sensor somewhere I feel. There is a sensor thats not fixed to anything just floating on its cable. It has the markings 953 No 9. Is this a temperature sensor that should be clamped to something that gets hot? Would this give me a diagnostic code 11 or 16?

[Northern Bongolow]

is that the little black square block hanging at the side of the diesel pump.

[AndyH]

Yesterday whilst earthing the fuel tank, (the gauge now reads full when full), I decided to wiggle every electrical connector block that I could see and leave both batteries disconnected with the headlights on over lunch. Lo and behold, upon reconnecting the batteries no hold light! Overdrive was not reached till over 40 mph and would kickdown again. The hold button was working, which was a shock at nearly 50! Alas after a couple of minutes the light came back and normal behaviour was resumed. However upon stopping and restarting no light for about 30 seconds and then hold light fault. I'm getting closer! Some bad connection or sensor is putting the gearbox into a limp mode I guess. WD40 on all the connector blocks is next I fancy.

[AndyH]

Hi NB. Yes, the free floating little black square that unplugs. What is that thing?

[Northern Bongolow]

its 13-1552 on the bottom of this drawing, if you click on the drawing number it opens up on the left as a resistor. it also shows where it should sit, in a little slide mount.

http://lushprojects.com/bongopartsmk2/c ... no=.html#1

[g8dhe]

Not certain but I think its used in calibrating the pump for the right fuel level injection, given the table of values to be selected from on the diagram.

[AndyH]

Thanks Geoff and Vanessa. I guess I can just secure it and ignore it.

I've found I can get rid of the flashing hold light and kickdown problem temporarily by stopping and restarting the engine, even whilst coasting in neutral. It still comes back though. A proper connector block clean up is next.

[AndyH]

Sorry for the late reply. I'veach had trouble logging in.

I can report that a new throttle position sensor (TPS) has vastly improved things. The hold light no longer flashes, gear changes are smoother, kickdown now happens sometimes but not always. It still sticks in too high a gear on the hills sometimes but at least I can now hit the hold button.

This result was only achieved with the TPS at the very extreme of its adjustment (it mounts with screws in slots so it can rotate a little). I got the new sensor from Japan at considerable saving. It comes with wiring and plug and also the socket for the mystery resistor I mentioned previously. I'm now wondering if this resistor is to calibrate the TPS. Surely the hold button should only be needed when the van is fully loaded with 8 passengers and not when empty? Perhaps a different resistor would allow me to further tweak the position of the TPS?

However the van is now much improved and I used it to tow my sailing dinghy around the race meetings all season.

Thanks for your help everyone.

[mikeonb4c]

Thanks for the update Andy, it did sound to me like the TPS was worth eliminating from enquiries although as you imply the extreme setting makes you wonder if another problem may be lurking behind it.