Trooper 1100 RPM hang-up

dirtydog · February 2, 2012

Hello.

I'm hoping the Trooper Forum can help me with a nagging problem on my 08 T4. When the vehicle is moving, the RPM's hang up sometimes between shifting and also when I push in the clutch and roll to a stop. Shifting at RPM over 4000 it sometimes stays there (doesn't drop down between shifts). If I put in neutral and roll to a stop it hangs at about 1300 RPM. Once the vehicle comes to a complete stop the RPM drops to 900 like it should. I cleaned up all sensors in the intake throttle body and just replaced the throttle cable but problem remains. Otherwise this rig runs awesome, but my mechanic background makes this really annoying. After reading too many posts on this forum I'm pretty sure I have one of the very early 08 models. Any ideas would be appreciated.

Dirtydog in Phx>

February 2, 2012

For starters, I would disconnect the Idle Air Control on the throttle body. Just unplug it. Also try putting an extra spring on to help pull the throttle all the way closed. I'm use the extra spring to solve a simular problem. Replacing the throttle cable itself isn't enough. I had to replace both the cable and sheathing. I found that water could acculumate in the sheathing at a low point and just stay there rusting the original steel cable which left wire fragments in the sheathing.

Lenny

dirtydog · February 2, 2012

Thanks Lenny. The new cable came complete with new sheathing so that is covered. I will unplug the IAC test. If that doesn't work I will try return spring. Can't get my head around the fact that it only happens when vehicle is moving. Just doesn't make sense. Results will be posted after testing. Have a great day!

lowgear · February 2, 2012

My 08 does the same thing, I just unhooked the iac like lenny said, as far as the idle being a little high when you stop then falling back down I was never able to find the problem to correct. If you disconnect the speed sensor it will probably quit doing it, but you won't have a speedo. I left it connected and put up with it like it is, yes it is very annoing. If you find out what it is let me know.

dirtydog · February 3, 2012

Thanks Lowgear. Did you try unplugging the speed sensor? I have thought of that but hesitated unplugging things due to brittle nature of connectors on this beast. I will post any/all remedies I come up with.

rocmoc · February 3, 2012

Hope you find the cause and post the fix. Hang in there!!!!!

rocmoc n AZ/MX

lowgear · February 3, 2012

Yes I unplugged the speed sensor to find my problem but I plugged it back in I want to know how fast I'am going because I drive my on the street a lot. It's OK to unplug just be sure you squeeze the wire retainer enough so it will pull off easy.

dirtydog · February 6, 2012

Unplugged speedo sensor and problem fixed! Now what to do? Can I live without speedo?? Will new sensor fix the problem? Does sensor send signal to computer or only to speedo in dash? So many questions, so little time.....Thanks to all for advice.

February 6, 2012

Hook the speed sensor directly to the speedo. Thats what I did when I switched my computer to a Megasquirt aftermarket computer.

Lenny

dirtydog · February 11, 2012

Thanks Lenny. I will try to rewire the sensor directly to speedo. That should solve all my problems unless computer gets angry about lost signal. Oh for the good old days before computers and electronics.....not that they are a bad thing but it makes for increased difficulty for an old fart like me! Thank you all for your help and ideas. Happy motoring!!

lowgear · February 13, 2012

To answer your question wether to buy a new sensor, I tried it and it did not help I can't tell you what causes this problem but I did leave mine unhooked for about 50 miles and it didn't seem to have any effect on the ECU, but you my find out something different on your's.

dirtydog · February 14, 2012

I think the computer has to translate from Chinese to English so if I disconnect speedo sensor from computer then will it drive on the wrong side of the road??

It will probably be Sunday before I can get back to the rewire. Will post more info then.

Thanks everyone!!

February 14, 2012

I think your right about the wrong side of the road. You will also only be allowed to have one child.

Lenny

dirtydog · February 14, 2012

Lenny.

Regarding your previous post, can I just clip one wire from speedo sensor harness to disconnect computer?

If so, do you know which one? I can't get enough info from Joyner elec diagrams. Always looking to make things easier if others have travelled the same road.

Thanks!

PS: think of it, the peace of mind having only one child/juvenile delinquent per household. I came from a family of nine.......

February 14, 2012

When I changed my computer over to a megasquirt, It was easiest for me to just run a wire from the speed sensor directly to the speedo. Nothing goes to the computer from the sensor. If you can run without the speed sensor plugged in, just cut the wires coming form the sensor. Then connect the wire coming from the speedo to one of the wires coming out of the plug which is still clipped to the sensor. If one wire doesn't work, try one of the others from the sensor. Look at the back of your speedo and you should be able to see the color coding of the wire going to the back. You then should be able to find that wire in the rear wiring. Shouldn't be any reason to run a new wire.

Lenny

dirtydog · February 14, 2012

That makes sense. I will post results when done. Thanks again!!

lowgear · February 15, 2012

I sure hope his wiring is better than mine my wires not only change colors but also sizes frm front to back.

February 15, 2012

After you find the other end of the wire, check it for continuity from one end to the other. I agree, Joyners wiring is pretty scattered. If they would have just provided a good detailed schematic.

Lenny