post #1 of Old 04-29-2009, 11:24 AM Thread Starter
Sambox
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1996 XJ Cherokee 
 
Join Date: Feb 2007
Location: Tucson
Posts: 508
Tachometer reading fluctuates

I was driving down the interstate yesterday (65-75 mph) when I noticed that the tach would jump. I was cruising in 4th at about 2100 RPMs and it would jump up to 2400, then back down, the drop to 2000, then up again. I didn't notice any surging from the engine though.

Is there a sensor for the tach that could be going bad or is the flucuating a mechanical issue? Or do I not need to worry about it?


"Jeeps are the equivalent of barbies for men."-JaikYJ

1996 Cherokee XJ, All stock except for a Flow Master exhaust.........for now. He He.

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post #2 of Old 04-29-2009, 03:01 PM
dodger889
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1989 YJ Wrangler 
 
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If you are still orginal the signal comes from the ecm drives the tach.

A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
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post #3 of Old 04-29-2009, 03:58 PM
Smash209
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Did you recently replace the speakers with better, ie bigger magnet ones? Its the speaker next to the tach causing it to jump a little when the bass hits (ha... bass out of a 4x6)

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post #4 of Old 04-29-2009, 04:36 PM Thread Starter
Sambox
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Yeah, I'm all original and no, the speakers have not been changed...at least by me. This is the first time I've seen/noticed it happen.

So for it to fluctuate, the ECM is sending false signals? Is this indicating a bad ECM?

"Jeeps are the equivalent of barbies for men."-JaikYJ

1996 Cherokee XJ, All stock except for a Flow Master exhaust.........for now. He He.

http://www.cityprofile.com/forum/tucson/
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