Tach

[samsonitesamsonite]

My 88 was wired by someone other than myself before I bought it. I know the tach does not read right, it says that at 60 MPH I am running 3500 RPM (4.0 5spd 3.73 gears and 31" tires) how do I "recaibrate" the Tach, or "Re-wire"

 

[MAKG]

You take that 2.3L tach and throw it in the garbage, and get one from a V6 donor with EDIS.

 

[samsonitesamsonite]

the truck had an origonal 2.9 that i swapped for the 4.0, I thought that they had the same tach?

 

[MAKG]

That could be a problem as well.

2.9Ls have one coil. 4.0Ls have three.

 

[samsonitesamsonite]

is a gen 1 dash so how woud i fix the tach mike?

 

[MAKG]

There is probably a resistor you can change (I know there is between 4cyl and 6cyl), but I don't know the values. The resistor lives in the instrument cluster.

 

[Ozwynn]

sam, I am all for finding the problem but i don't think the 4.0L likes the gen 1 tach. it costs $30 for a sunpro tach at autozone.

 

[samsonitesamsonite]

yeah yeah.. I know john, I just like the stock look... I am thinking of stripping the motor down the the basics and going with a 1st gen exploder wiring harness and dash, that will solve more problems than one. Although, with the 96 spliced into my truck I have OBDII

 

[Ozwynn]

there you go, there is your problem. you are trying to use an OBD1 tach with an OBDII computer...... they don't like each other. Take out your factory tach and put the sunpro in the hole. you just need to find 1 that will fit. Are you using a cable or a VSS for the speedo and how well is it working?

 

[samsonitesamsonite]

Im using a cable and it's working fine, i changed my speedo gear with my tire size and when im running 60 mph i get radar'ed at 59

 

[Ozwynn]

how you gettin that to work with the obd2?

 

[Wicked_Sludge]

i think what hes getting at is the fact that the obdII computer has to have a speed sensor signal to function properly...but even gen 1's had a speed sensor in the transfer case, right?

 

[Ozwynn]

yeah, for the computer, the speedo still ran on a cable through 91. 92's had a VSS for the speedo. I am trying to figure out how he is using the older trans with OBD2 ..... i was under the impression that there were differences.

 

[Wicked_Sludge]

actually the speedo was cable driven untill 95 (when they switched to OBDII)...when the switched and ran it off the VSS in the rear diff. the computer has always used the VSS in the transfer case.

 

[samsonitesamsonite]

well i will say this much, I have no idea how its working, its out of a 96 explorer, that much I know for a fact. the guy that did the swap and wiring was an electrical engineer.