AW4 downshifting issue?

89 4.0 aw4/242/33" tires/3.55 gears

So, i have had this combo for awhile, and the problem has just started within the last few weeks..

When accelerating from a stop, it goes just fine.. shifts smoothly on time threw the gears.. but as soon as you get up to speed, the only way to shift down is manually shifting. flooring it will not do anything..

The tranny fluid looks fine, i have a minor leak at the pan, but it is still "full"

I have replaced the throttle position sensor.

I was advised to adjust the kickdown cable.. if thats the case.. HOW?

I expect it to be dog-slow, due to the gearing and tire size, but it should atleast shift down in the hills...

Cable adjustment: http://www.naxja.org/forum/showthread.php?t=1015963&highlight=adjusting+transmission+cable

X2..

Bump:
I have done the cable adjustment 10 different times now, tryed to ad slack, also tryed to make it a little extra tight.. everything.. to no avail! it just will not downshift! i have put about 500miles on it trying to figure it out.. it has gotten to the point where you have to manually shift if you need to accelerate after its in OD..

I know you already said you replaced the TPS... but could you measure the voltage at the input to the ECU itself perhaps? On an 89 it will be pin C7 (a yellow/green wire) if the 89 has a similar layout to the 88. Perhaps there is a break in the wiring harness somewhere and the input to the ECU has sufficient capacitance and insufficient leakage current to return to one end of the scale, but can be brought to the other end of the scale by the TPS... just a shot in the dark.

what should the voltage to this wire be? is this done at idle?

It'll range from a little over 0 volts to just below 5 volts depending on the position of the throttle.

Remove the four-wire connector from the TPS, turn key ON, check between pins D (grnd) and A (5 volt supply). Got 5 volts? Reattach the four-wire connector to the TPS, key ON and throttle plate fully closed, backprobe the connector at B (+) and D (grnd). Output voltage 4.15 volts? If yes you are done. If no, then attempt to adjust TPS so the output voltage is 4.15 volts. Adjusted to 4.15 volts, then TPS and wiring Ok; if can't adjust, then replace TPS and adjust to 4.15 volts.

If everything else checks out OK, check the "trans" fuse in the fusebox. It supplies power to the Power/Comfort switch. If it's blown, you will be in the default Comfort-Grandma mode and downshifts will not come easy. I found this when my P/C switch was shorted internally and blew the fuse. I wired it permanartly into Power mode by unplugging the switch and putting a jumper wire into the switch harness crossing the tan and the dark with stripe wire. Leave the black wire out of the equation.

nw-xj-scott said:

what should the voltage to this wire be? is this done at idle?

Click to expand...

It should mirror the TPS output at the TPS plug. You're just following the path of the signal back to the ECU-- the '89 uses a two plug TPS, though--

I think you'll want to find the pin location on the TCU that receives TPS signal and verify that the proper signal is reaching that point.

I'll see if I can find the pin location-- no promises.....

Pin "B" on the square TPS plug is output (should be about 4.15V with throttle closed)
Pin "D2" on the TCU should receive the same voltage from pin "B"