Archived My son needs help

[edgeman]

My son is heading back to collage tomorrow and his 96 CTD, auto transmission, started acting up today. The tach is jumping up and down, and it wont stay in overdrive. It kinda sounds like the throttle position sensor? This is his only transportation, and he has a 10 hour drive back to welding school. Any ideas? Thanks, Larry

 

[RCorbeil]

Will need more info. Does the engine rev or is it the tach that is acting up?

Ron

 

[HBarlow]

I've never owned a 12 valve so don't know much about them but when the APPS died in my '01 the engine simply ignored me and my desires and went to idle speed.

Sounds like the truck may have lost the speed sensor. Is it on the differential on a '96? With erratic speed input the engine and transmission don't know what to do.

 

[edgeman]

More info. When the tach starts jumping, the engine does not change RPM with the tach, but, the transmission does start comeing out of OD at about the same time, and of corse the RPMs do change at that time. He said, driveing 60 mph, the transmission comes out of OD and then starts hunting to get back in OD. I told him it sounds like the TPS, but we dont even know where it is or what it looks like. Also, I have herd other TDR members on this forum saying something about being able to clean them, we would try this if we knew where its located. Thanks

 

[DavidC]

Could be the crank sensor. I believe it is visible by the damper on the front of the engine. There has also been frayed wiring to the sensor and the plug that is there also. Others with more 12 Valve experience may chime in but I would look at that sensor and wiring in the mean time.



Dave

 

[Missouri Mule]

With a quick glance of your symptoms I going to say it is your Engine Speed Sensor (crank position sesnor)/connector/wiring located to the left of the vibration damper.





The ESS sends a signal to the PCM which sends a signal to the tach. But the PCM also uses the data to control shifting into overdrive.

Besides sending data for the tach and the overdrive the PCM also uses the data for the A/C, the ESS also activates the Automatic Shutdown relay which sends line voltage the EVR(electronic voltage regulator) in the PCM.



Sometimes not all the symtoms appear just a few.



5-volts wire violet/white provided by PCM

signal wire grey black

ground wire black/light blue provided by PCM



The TPS is located near the Injection pump and should be attached to throttle linkage.

Looking at 96 Factory Service Manual the ESS,TPS and the Vehicle Speed Senosr send data to PCM which determines when OverDirve is used( Your not loosing the speeddometer and its not unlocking the Torque Convertor Which needs input from all three ESS,TPS,VSS like overdrive.

 

[GaryOwen]

Sounds like the same problem I had and it was the TPS. I tried cleaning it and it helped some, but not completely. I drilled a couple of small holes in the side of the TPS and squirted some contact cleaner inside. Shook it around a some and reinstalled. I helped some, but ended up getting a new one at NAPA. Seems like it was in the $150 range. Do a search for "TPS location" under 12-valves and you should find plenty of info.



Your TPS is located on the front-left corner of the engine. Looking over the driver side fender, find and follow the throttle cable to its end. You will also find the end of the cruise cable at the same location (if you have it). There is a black box bolted to the side of the assembly that the cables run too. This is your TPS. It has a three prong cable attached.

 

[MMeier]

Check the plug for the CPS, it should be on the front side of the cylinder head. Pull apart, clean and coat with some dielectric grease and put back together, check back !

 

[DGamelin]

We just had a truck in the shop that had the speedo jumping up and down trans not shifting right and the check engine light flashing on and off but no codes. After a lot of time wasted it was the alternator, it was in bad shape. It almost looked like it had been on fire, we were guessing it was spiking the computer then shorting out back and forth. I know this odd but it's a place to look. Good luck



_________________________

93 250 2wd xc 354 auto 280k

04. 5 3500 4wd qc dully 373 6speed

 

[p-Bar]

We just had a truck in the shop that had the speedo jumping up and down trans not shifting right and the check engine light flashing on and off but no codes. After a lot of time wasted it was the alternator, it was in bad shape. It almost looked like it had been on fire, we were guessing it was spiking the computer then shorting out back and forth. I know this odd but it's a place to look. Good luck



_________________________

93 250 2wd xc 354 auto 280k

04. 5 3500 4wd qc dully 373 6speed

This is cheap to do, put a volt meter on the truck and drive it and see if their are any voltage spikes. Cigarette lighter or any place that you can get power from will work.

 

[edgeman]

Thanks for the replys. Here is a short up date, my son found the TPS, pulled it off and cleaned it the best he could. That helped, but didnt fix it. So he now is going check the ESS (crank sensor) and if that dosnt help, hes going to rob the TPS from his brothers 97, and see if that does it. Im liveing (working) 14 hrs from home and cant help with this, other than talking with you TDR members. Thanks again. I will update as soon as I hear something.

 

[HBarlow]

We just had a truck in the shop that had the speedo jumping up and down trans not shifting right and the check engine light flashing on and off but no codes. After a lot of time wasted it was the alternator, it was in bad shape. It almost looked like it had been on fire, we were guessing it was spiking the computer then shorting out back and forth. I know this odd but it's a place to look. Good luck

_________________________
93 250 2wd xc 354 auto 280k
04. 5 3500 4wd qc dully 373 6speed

This suggestion makes a lot of sense. I've never seen the problem but I have a vague memory that something like this has been reported and discussed on the TDR website years ago. Alternators do wear out.

 

[fox]

Thanks for the replys. Here is a short up date, my son found the TPS, pulled it off and cleaned it the best he could. That helped, but didnt fix it. So he now is going check the ESS (crank sensor) and if that dosnt help, hes going to rob the TPS from his brothers 97, and see if that does it. Im liveing (working) 14 hrs from home and cant help with this, other than talking with you TDR members. Thanks again. I will update as soon as I hear something.

Swapping the TPS's would be a good idea. cheap and if the problem moves you are sure what the issue is.

 

[edgeman]

Ok, he found the problem!!!! It was the crank sensor. Somehow the wire got moved and the belt cut the wire. A new one is just under $100 and would have to be ordered, so he spliced it back togather. He took it for a 20 mile test drive and all is well. Thanks to all who helped. He now knows where the TPS is, and how to clean it. Also he knows what the crank sensor does when it acts up. I hope his trip back to welding school goes well. Thanks again, Larry