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Anyone familiar with the Jeep 4.0L


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#1 TAHOE OFFLINE  

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Posted July 01, 2016 - 08:39 AM

So my son has a 2000 Jeep Cherokee 4.0L auto that's giving us fits. It's throwing all kinds of code and runs like dog poop at idle. Sometimes it fires right up, others times it spins 8-10 times before firing. It will run fine after idle sometimes, most of the time it misses good until it warms up, almost like it's got huge cam in it. It seem sto have rough idle all the time though.

 

We have replaced

*both O2 sensors

* all 6 injectors with upgraded brand new ones

* Crank position sensor

* Cam position sensor

* Coil rail

* plugs

* cleaned IAC

 

Not sure what direction to take

One of the codes it was throwing was a "no trans bus" code which a buddy of mine told me that's usually on indicator of ECM going bad.

 

I am trying to keep from going to a shop, but looks like I may have no choice.


Edited by TAHOE, July 01, 2016 - 08:40 AM.

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#2 Sawdust OFFLINE  

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Posted July 01, 2016 - 09:08 AM

Marty my friend your in a pickle. We have a 1999 GC with the 4.7 & my son has 2002 Dodge Ram with the 5.9. Between these two vehicles in the last two years we have had enormous electrical problems that cause both vehicles to do crazy things because if so many signal codes. Go on YouTube & look at the problems these Chrysler are having. Some qualified dealers can't figure out their problems. Class action suits are being requested all over the map. All I have done is to retrieve the codes & from there. Vehicles will run just fine for days or weeks & it's another code. Good luck.

#3 TAHOE OFFLINE  

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Posted July 01, 2016 - 09:20 AM

Marty my friend your in a pickle. We have a 1999 GC with the 4.7 & my son has 2002 Dodge Ram with the 5.9. Between these two vehicles in the last two years we have had enormous electrical problems that cause both vehicles to do crazy things because if so many signal codes. Go on YouTube & look at the problems these Chrysler are having. Some qualified dealers can't figure out their problems. Class action suits are being requested all over the map. All I have done is to retrieve the codes & from there. Vehicles will run just fine for days or weeks & it's another code. Good luck.

 

Thanks for the pep talk Jim haha

I now own 3 Chrysler vehicles, not sure what I've been thinking. :wallbanging:  The Durango isn't even on the road yet, not sure what that bundle of joy will bring us :(


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#4 Mtypython ONLINE  

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Posted July 01, 2016 - 10:01 AM

Check the throttle position solenoid and fuel pressure is all i can thhink of
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#5 Sawdust OFFLINE  

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Posted July 01, 2016 - 10:42 AM

Just a thought Marty on our GC rough idle, staled,hard to start & died a couple times. Code read too high voltage to MAP sensor...but MAP is good. A buddy said it was a false read so just take positive lead off of battery for a minute to reboot & problem was solved.

Edited by Sawdust, July 01, 2016 - 10:42 AM.


#6 DougT ONLINE  

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Posted July 01, 2016 - 11:09 AM

When you replaced the cam sensor, did you check the timing of it? Did you check the slop in that drive gear. The gear is prone to wear. I've seen the teeth totally gone. As for the electrical problems, start with the grounds. Take them off and clean them. Clean the battery posts good. Maybe even add a body ground and block ground. Anything that could short the 5v reference could cause a bus code. Do you have a scan tool or just a code reader?


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#7 Sawdust OFFLINE  

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Posted July 01, 2016 - 11:17 AM

Wow Marty I'm brainstorming. I just remembered years ago I changed a few sensors & had to have my computer reset at the dealer so it would recognize the new parts.
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#8 TAHOE OFFLINE  

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Posted July 01, 2016 - 11:37 AM

Just a thought Marty on our GC rough idle, staled,hard to start & died a couple times. Code read too high voltage to MAP sensor...but MAP is good. A buddy said it was a false read so just take positive lead off of battery for a minute to reboot & problem was solved.

yea, I've done that every time we've worked on it. Seems to help for about 5 mins then it starts up again.

We have managed to cure a dead miss we had with the injectors and coil rail, but it's still got the hard start and rough idle.

I was thinking the MAP maybe a cause, about the only thing I have replaced.

 

When you replaced the cam sensor, did you check the timing of it? Did you check the slop in that drive gear. The gear is prone to wear. I've seen the teeth totally gone. As for the electrical problems, start with the grounds. Take them off and clean them. Clean the battery posts good. Maybe even add a body ground and block ground. Anything that could short the 5v reference could cause a bus code. Do you have a scan tool or just a code reader?

 

no, I just pulled the cam sensor off and replaced it, did not pull drive up and out.

We've got new terminals on the battery and it's clean, but I told my son it could be even something as simple as a ground wire somewhere. It's got a engine to body strap on it, maybe I need to remove and clean real well.

We borrowed an actual scanner that we could clear codes and watch live reads as it was running. It was throwing so many different codes that last time we did it we weren't sure where to start. It was reading high on front O2 and really low on rear one so we replaced them both, didn't help much.

 

 

I had thought of low fuel pressure too, was going to change filter, but it's only a sock inside the tank :wallbanging:  :wallbanging: :mad2:  :mad2:  


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#9 DougT ONLINE  

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Posted July 01, 2016 - 01:37 PM

 

 

no, I just pulled the cam sensor off and replaced it, did not pull drive up and out.

We've got new terminals on the battery and it's clean, but I told my son it could be even something as simple as a ground wire somewhere. It's got a engine to body strap on it, maybe I need to remove and clean real well.

We borrowed an actual scanner that we could clear codes and watch live reads as it was running. It was throwing so many different codes that last time we did it we weren't sure where to start. It was reading high on front O2 and really low on rear one so we replaced them both, didn't help much.

 

 

I had thought of low fuel pressure too, was going to change filter, but it's only a sock inside the tank :wallbanging:  :wallbanging: :mad2:  :mad2:  

High O2 voltage means low oxygen. (rich condition) The MAP can cause a rich condition if the voltage is higher than normal. At idle with 18-20 in vac you see 1.0-1.4v. Another common  item to cause a rich mixture would be a coolant temp sensor that shows too low. It should start out at ambient temp with a cold engine and come up to the 195 operating temp if the T-stat is good. They won't set a code if it's in the operating range but can cause other codes to set. TPS should be 1v or less at idle and stay steady. If it is jumping around it can cause unsteady idle and rich condition. If you're in doubt of the MAP you can unplug it and run the engine. The ECM will use a default setting and you will usually be able to tell a difference, I've seen the ground straps corrode and not conduct as well. You can check the gear slop in the cam sensor somewhat by turning the shaft from the top to see the back and forth slop. Clear the codes and record the ones that return and their definition. Maybe we can see a common cause.


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#10 ckjakline OFFLINE  

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Posted July 01, 2016 - 02:23 PM

On the timing note,maybe your timing chain has excessive slop.Put a socket on crank pulley and see how far you turn engine until rotor moves,if it has a distributer.(i'm not sure when they stopped using them).That was an issue on my 90 xj.


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#11 toppop52 ONLINE  

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Posted July 01, 2016 - 03:33 PM

The ECM is likely failing, one day it will not start, but it might start the next time, it will progressively get worse. It's sprung up a whole industry of rebuilding PCM/ECM's. When I wa service manage rat the dealership, we ordered them from eBay. There is a chance your harness either to the ECM or some sensors, is bad or corroded. I would try unplugging them and spraying electrical cleaner in the contacts. Best way to test the ECM is to use a rubber mallet and tap it while idling to see if there are any changes.


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#12 propane1 ONLINE  

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Posted July 01, 2016 - 04:01 PM

I would look for a vacuum leak. Intakes, hoses and any thing operated by vacuum. Things could leak when hot or cold or all the time. Just a thought.

Noel
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#13 glgrumpy ONLINE  

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Posted July 01, 2016 - 09:46 PM

Well, I had a Jeep with one recently.  The hose from the charcoal canister to the manifold was kinda soft and kept falling off the manifold fitting, specially if it back-puffed a bit when starting. Ran like crap at idle till put back on. Mine kept just stopping, like you pulled  the plug and left me by side of road many times. I worked on it for long time checking and replacing things. All it was was a box in fuse box under hood that said ASD, Automatic Shut-down. Pulled that and replaced, ran instantly.  Did again on road. Had extra relay, put it in, good to go for awhile. Kept doing this on and off at wrong times, then one day, that didn't work. Even the starter never cranked. Replaced key switch in column, then even that didn't work. I ended up selling it as is, was tired of it.  Another thing that goes bad on these a lot and makes odd things go on, is the crankshaft position sensor switch. It is really down on the trans bellhousing area at an opening, and reads off the flywheel, kinda crude, but worked. I've seen those go bad on a couple and once changed was good. It is a PIA to reach up there, best from underneath car and long arms, ha! Right near exhaust too, so don't do when hot!



#14 olcowhand OFFLINE  

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Posted July 01, 2016 - 11:44 PM

I've had a few Jeeps with the 4.0.  2 gave me fits, and both times led me to buying a new ECM.  Of course I wasted a bit of money throwing new sensors & such on it first.  :wallbanging:


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#15 TAHOE OFFLINE  

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Posted July 05, 2016 - 05:29 AM

I've had a few Jeeps with the 4.0.  2 gave me fits, and both times led me to buying a new ECM.  Of course I wasted a bit of money throwing new sensors & such on it first.  :wallbanging:

 

 I remember you fighting with your GC.

 

I check grounds and cleaned them. The strap from motor to firewall only had like 4 small strands holding it on. Fixed that, not much a difference. I removed MAP sensor and clean out the little port, didn't make much of a difference either. It seems to idle better, but now has delayed start up, still spins 8-10 times to start when cold.

I drove the thing all last week while my son was in Florida. He comes home and first day he drives it calls me from Walmart, won't start. :wallbanging:  I banged on starter with hammer and started to spin, but then stopped, it was locked up. Changing a starter in a Wally's parking lot is not a fun Sunday afternoon, but it spins motor much quicker now.

Still need to try to borrow my buddy's scanner and see what TPS and MAP sensors are reading. It runs fine once above 1000 rpm, just hard start and rough idle.


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