Just recently I started experiencing a lot of issues with my jeep that were not present before and i am not too sure how to go about trouble shooting.

1: A while ago I had a battery die on me and after replacing I found that my battery gauge is reading 17 consistently or at least it was until the other day. (It may not be 17 but it is ever so lightly always dipping in the red above 15)

2: Now I am getting constantly fluctuating readings only my gauge for my batter anywhere from 9 to 18 while I am driving.

3: My engine idle is getting rougher even though I am off a fairly recent tune up. (plugs, wires, distributer cap, oil. fuel filter)

I don't want to jump to anything too crazy and just worry myself so I am looking for advice. That being said if I do end up needing a new pcm how would I go about finding out what I am looking for ( I have a jeep Cherokee sport 1994 ).

 

Start by checking your battery connections and cables. Check that alternator to battery connection, too. Remember to check the grounds. And don't be gentle with checking those cables. Corrosion can wick up inside and do a lot of damage without being obvious. Pull, push, and yank. If it's marginal, you want to break it. That way you know it's broken and you can replace it.

And don't just look at your connections. Take them apart and make them clean! Shiny bare metal! For all but the battery terminals, slap on some dielectric grease before you reassemble them.

And do NOT use these crappy auto-parts-store terminals! Any terminal that clamps bare wire down with screws is asking for trouble. Just don't do it. (Okay, in an emergency, like a spare tire, yes.)





Some guys like to use marine terminals. I prefer military terminals. They don't stick up as much and they give you one more mounting point for the cable. I get cables custom made by BestBoatWire.com. Do the clear heat shrink, on the ends. That way you can keep an eye on things. Great prices and excellent quality. When I did mine I went one size bigger than stock. So, for the main cables, I got 4 gauge, as the stock are 6 gauge. Don't go crazy - there is no real benefit to going with monster cables here.


So, yes, it could be your PCM, but it's more likely one of your connections is flaky. Can't hurt to renew them.

 

This is great advice thank you, do you happen to have a rough estimate of how much wire I might need specifically of the 4 AWG I am going order some and just don't want to under or over order.

 

Get a multimeter and check to see what the voltage actually is. Could be a bad gauge too.

 

What should I be measuring with my multimeter, apologize if it is a kind of noob question but i am new to cars in general.

 

Multimeter set on DC Volts 20 scale. Black probe on battery negative red probe on battery positive. Measure with car off and car running. If those are both ~13.0 volts, with car running bang on dashboard. If fluctuation recurs start looking for loose wire or solder connection.

Alternatively, if battery readings are normal cover voltmeter with black tape.