Weird issue after reseting PCM
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Professional
Joined: Oct 2010
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From: Big Rapids, MI
Weird issue after reseting PCM
I have two Chrysler products, one is a 97 Jeep Grand Cherokee Laredo with the 4.0, and the other is the Ram in my sig.
The other day it was actually nice outside, so I decided to do a few things on both vehicles. The major thing I did was to disconnect both cables from the battery and clean the terminals up. With the cables off, I turned on the headlight switch and turned the key to on to drain any residual charge and reset the PCM. (I hope that was the correct way.)
Anyhow, after hooking everything back up, I started both vehicles. The Jeep was first, and I had to crank and crank on it to get it to fire. After it started, it ran rough until I revved it up a few times, then it seemed to smooth right out. I let it idle for about ten minutes then shut it off.
When I started my Ram, there was no problem at all, and it fired right up and idled nice and smooth.
What I am wondering then, is why the difference in starting when I did the same thing on both of them?
I'm kind of confused, as I have never really messed with doing that on a vehicle before.
The other day it was actually nice outside, so I decided to do a few things on both vehicles. The major thing I did was to disconnect both cables from the battery and clean the terminals up. With the cables off, I turned on the headlight switch and turned the key to on to drain any residual charge and reset the PCM. (I hope that was the correct way.)
Anyhow, after hooking everything back up, I started both vehicles. The Jeep was first, and I had to crank and crank on it to get it to fire. After it started, it ran rough until I revved it up a few times, then it seemed to smooth right out. I let it idle for about ten minutes then shut it off.
When I started my Ram, there was no problem at all, and it fired right up and idled nice and smooth.
What I am wondering then, is why the difference in starting when I did the same thing on both of them?
I'm kind of confused, as I have never really messed with doing that on a vehicle before.
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Joined: Apr 2010
Posts: 87,403
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From: Clayton MI
I would take a look at the IAC motor, and passages on the Jeep. Sounds like they are getting gunked up. 
WHen you reset the PCM, it has to relearn how to idle the engine. Sometimes are more successful than others...
WHen you reset the PCM, it has to relearn how to idle the engine. Sometimes are more successful than others...
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Professional
Joined: Oct 2010
Posts: 174
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From: Big Rapids, MI
Ok, thanks. I will do that the next time we have a halfway decent day.
Does it sound like I did the reset correctly? I noticed my truck seems to run a little bit better now. Of course, I just had the water pump replaced, so there isn't near as much drag on the accessory drive now.
My next project is to do a good tune up and complete fluid changes on both vehicles. As soon as I get moved and have a garage, I plan on hitting the maintenance a lot harder.
Does it sound like I did the reset correctly? I noticed my truck seems to run a little bit better now. Of course, I just had the water pump replaced, so there isn't near as much drag on the accessory drive now.
My next project is to do a good tune up and complete fluid changes on both vehicles. As soon as I get moved and have a garage, I plan on hitting the maintenance a lot harder.