Engine/Transmission (1998.5 - 2002) Eratic tach, engine missing due to loose battery terminals?

[jebia]

I drove out to Prescott AZ from Albuquerque (400 miles), NM this weekend. The truck ran great to Prescott and drove it a bit around town during the week end (some of it on very rough wash board type gravel roads, shock up the truck quite a bit).



When I started the truck to return Sunday evening, I noticed the idle was bit eratic (not wild 500 rpm swings), the tack was moving between +/- 50 rpms (idles about 800 rpm). I decided to get going, hoping it would smooth out (my fuel pressure was rock steady at 17 psi, and my voltage was a solid 14 volts).



On normal level roads the truck would stumble a bit (like one of the cyclinders wasn't firing from time to time (kinda of like a car with a bad spark plug wire). Under load (climbing a hill it was worse, bucking a bit). I drove about 100 miles.



I stopped in flagstaff for gas and noticed the positive terminals of both batteries were loose (I could rotate them with my hand around the post). I recently installed two new optima red tops and I guess I didn't tighten then enough, so when I drove those gravel roads, they vibrated loose on the posts. I immediatley tighted both terminals hoping this could fix my eratic idle. I started the truck but the idle was still just as eratic. I continued on and about 15 miles down the road everything smoothed out.



I stopped again in Grants NM and upon startup, the eratic idle came back, this time though the truck smothed out in about 5 miles.



When I got home I started the truck up again, and it started up smooth. I did then disconnected both batteries, and in the mourning I re-connected them and when thru the apps calibration procedure. It started up fine, nice smooth idle. I'm still confused on why this all happened.



My question is, do you think the loose battery termination caused the apps to act eratically (lose its calibration, low voltage at startup)? Did the ECM/apps, after I tighted the battery terminals, need the 10 miles or so to "re-learn" its calibration?



PS, I had this problem a few months ago, and at that time I replace the apps (the idle swings were a lot wilder) with a new one from mopar 4 less. Since then I hadn't had a problem.



Thanks in advance.



Jon

 

[PC12Driver]

Maybe the Cam Position Sensor? That controls the timing and provides the tach info. Any codes?

 

[jebia]

PC12driver,



You may be right, no codes were set, no check engine light.



By coincidence, I have a new came sensor sitting in my garage. I ordered a cam sensor a few months ago, when I replaced the apps, but held off on install for two reasons:



1)after installing the apps I hadn't had another incidence of eratic tach operation.



and



2)At the time I ordered and was waiting to recieve the "improved/heavy duty starter" contacts to come in (thinking it was easier to due both at the same time).



Jon

 

[CumminsAholic]

It's the crank position sensor that's by the starter (at least on my 98. 5 maybe the newer ones are different?) and I'd bet that it's your problem. I had an erratic tach, thanks to TDR I pretty much knew it was the crank sensor, it was. I just didn't want anybody else to get the wrong sensor if they had a similar problem. I got mine from the local Cummins shop.

Corey

 

[jebia]

Thanks Corey, I'll change it out this weeked.



Jon