87 Cherokee won't up shift

[Bullet3600]

I pressure washed the engine over the weekend and no my 87 Cherokee with a 4.0 won't upshift and stays stuck in 1st gear. Everything worked fine before the wash. I sprayed some quick dry around the TPS but still no luck. Any help would be appreciated.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[Bounty__Hunter]

Pretty common. Could be a bad TPS, they're easy to check with a multimeter.

Check here for some troubleshooting tips. I've got this same problem in my '88 MJ.
http://www.transonline.com/transdige...ers/index.html

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[graewulf]

also check the trans fluid.. i know its a long shot, but water in the fluid would cause shift problems.

[Bullet3600]

Thanks for the info. I will try those steps on Saturday when I make time. The Trans fluid is clean and a nice red, but was also wondering if some junk or something broke loose in the pan and clogged something. This is very frustrating having to share only one jeep with the wife.

[LBR]

Don't know this particular engine/tranny setup, but does this automatic have a vacumn actuated modulator? If it does, the pressure washing could have blown a rubber line off of the modulator. A lot of older trannys will not upshift if that vacumn line is not "talking" to the modulator. LBR

[Bullet3600]

Well I changed the TPS and still no luck, Time for step 2.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[MudderChuck]

Originally Posted by Bullet3600

Well I changed the TPS and still no luck, Time for step 2.

Did you check the fuse behind the glove box? There is one is the harness near the TCU, for the TCU (tranmission control unit).

[Bounty__Hunter]

Pulling the fuse behind the glove box for the TCU should allow you to manually shift the tranny. This will rule out mechanical failure inside the slushbox.

[Bullet3600]

Well the fuse checked out ok, does anyone know where the vacuum modulator is located on the trans?

[MudderChuck]

There isn´t a vacumm modulator in the AW 4 that I know about.
I´d check power first, there is a 7.5 amp fuse in the fuse block, the 15 amp fuse behind the glove box and a fusible link, probably near the starter relay, behind the battery.
Next check would be the TPS, what is your input voltage, output voltage and how does your ground wire test for resistance? 4 pole connector at the TPS. Normal input voltage is around 4.65 or so, no matter what the book says. The output voltage should be around 3.85 but the tranny will work just fine up till about 4 volts or so. The check is made with the plug connected ( straight pin through the wire), the ignition on and using the 4 pole plug (TCU) ground, not a chassis ground to test.
A TV (transmission Valve) cable adjustment, might also cause problems. But with a miss adjusted cable, it will usually eventaully shift. or have really soft slipping shifts.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).