Hi. I've got a '99 XL with the 4.2 and 5-speed, but no tach. I went to Autozone earlier this week and picked up one of their cheap Sunpro tachs, later to find in the instructions that it isn't compatible with my truck. Well, I didn't want to accept that, so I read around and saw that many people were connecting their tachs to the PCM on pin 48. I took this approach, drilling the hole out at that pin in the harness and running the wire there. Much to my excitement, it seemed to be working. It was showing a reasonable speed for idle. Well, I pulled a little on the throttle cable to find disappointment. It was responding to the change in engine speed, but I'm pretty sure it wasn't accurate. It went up to about 2k, while I'm sure the engine was beyond 3k. Has anyone else had this problem? Should this actually work, and my judgement on the engine speed is completely wrong?

 

thats how we wired my roomates shift light in his old car. was more accurate then the tach. But the problem is, that your (cheap) anolog tach isnt as fast or accurate as a digital gauge would be..... umm actually i think its anolog or electric.. idk

 

On v8 engines, an adapter is used to drive a standard tach.
Auto meter has an adapter for such purposes but I don't know if a 6 cylinder would still readout correctly as most tachs are calibrated for a v8.
Good luck.

 

Thanks for the responses...

What exactly does the adapter do, do you know? This tach actually has a switch for 4-, 6-, and 8-cylinder engines, but I assume that was for calibrating with the distributor. I've installed another tach (in a friend's car... already had a tach in the cluster, very easy...) that was adjustable for cylinder count, though not quite as easy as a switch...

Anyhow, is the adapter itself universal or is that made for certain engines or ignition systems?

EDIT: ah, AutoMeter... I guess I can go to the site and answer my own questions...

 

if the crankshaft isnt a "splayed" crankshaft then you need to set it up as a 4cyl tach