1990 4.0 auto TPS adjustment?????

[gl1200aman]

I used the 4.0 jeep renix fuel injection manual that was referenced in another post to try and adjust the TPS on the 90 comanche that I recently bought. It stated that using a digital multimeter the reading between wires A and D should read 5V and then adjust so the reading between wires B and D should be 4.15 giving 83%.

 

I only get 4.67V between wires A and D. I adjusted it to the 83% per the manual and it jerks/sputters worse. I now adjusted the reading between wires B and D to the 4.15V and it runs pretty good. The battery is fully charged.

 

The questions I have is: Why would the voltage between wires A and D be 4.67 and not 5V as stated in the manual? What controls that voltage? Could the lower input voltage be the problem?

[juan]

You are asking 20 year old wiring to have a perfect text book voltage reading - bottom line is not going to happen. Maybe when the jeep was new the reading was 5v but after 20 years the is going to be some resistance in the wires therefore you are going to read less - actually 4.67v is not bad at all, adjust to about 20% of that reading, if it does not work adjust manually by feel untill the jeep runs to your liking.

[gl1200aman]

Thanks for the reply. I did assume there could be some drop with age but was hoping that there was a way to correct it or a part that controls the voltage to replace. I have it adjusted to run pretty good.

[Pete M]

if you can get it to run good, then that is all that's important. :thumbsup:

[bigalpha]

What do you do if you adjust the TPS while the truck is running but the idle still isn't normal? Replace the TPS?