my jeep has none of those symptoms will start up with no problem and run a lil rough just wont stay running if let it idle below 1500 RPMs. could do it all day and would do the same thing all day start up normal then get to idle speed and wants to shut off and give it gas and keep above 1500 will run all day but wen put in a gear to drive just bogs out.

 

has the iac been checked?

 

your tlkin about the idle air control sensor on the intake right cause i replaced that sensor to.

 

Well that's completely different than what you started out saying - try to be more specific next time.

Check you battery voltage. A dead/dying/weak battery will cause this problem. Since you already replaced the TPS, this would be my course of action. Battery voltage should be around 12.4v with the engine off, 14.2v engine on.

When you let the battery run dead or disconnect it for an extended period of time to do some work, the engine computer ( ECU ) gets re-booted and the idle settings are deleted. The engine will be difficult to start and as you describe it will die unless you keep on the gas pedal. After a short period of time it will idle normally.

This should only happen once after the dead battery or work session. If you find it is happening often, your battery is probably bad. The battery may have enough power to start the motor, but the low voltage re-boots the ECU. Check that all the battery and starter wires are clean, undamaged, and are firmly connected. Have the battery load tested at a shop or parts store.


You can also try the pcm reset procedure.

1. Disconnect both battery cables and touch them together for 30 seconds.
2. Reconnect battery cables.
3. Turn ignition to "on" (do not start)
4. Headlights "on"
5. Headlights "off"
6. Ignition key "off"

 

ok so i went ahead and did all the steps and still runs the same the sensors are good so i went ahead and bought the new computer. now can you guide me in how to install the new one? cause i know there are a few things you must do but probly not all of them. so your help is greatly apprecited and thank you for the previous post it helped alot!!

 

undo ground connection on battery. undo connector(s) at ecm, remove and replace ecm, reconnect connectors (do not overtighten if it has a bolt in it), reconnect ground at battery. Start vehicle, may have trouble idling and runnign for a few moments, and may drive funny for a few miles.

 

Come on now you must have a bit of common sence in there right?

 

ok so now what do i do the computer did not fix the problem still doing the same thing i am stumped what else could be causeing this?

 

Sorry I must have missed something. What are all your symptoms? Is it possible it could it be possible that it could have jumped time? This does happen sometimes where your timing chain gets loose and moves about a tooth and wont start. Like I said I missed where it said what your exact problem was so I could be way off.

 

Map sensor? have you checked all your plugs and wires? my jeep wouldnt stay running when it was moist out because the cap and rotor and wires were old replaced that greased em up havnt had a problem. maybe your coil is going out. have you checked fuel pressure?

 

what codes is it throwing mine was running bad like this and found that it had multiple random cylinder misfire i changed all the sensors and the ecu, finally took it to a shop and it was a bad temp sending unit and a wire to the injectors.

 

This is extremely unlikely on the 4.0L engine

 

It is unlikely but not unheard of. I have seen it before. I am just saying I would not rule it out and not check it before throwing 100's of dollars hoping it fixes it.

 

Start with the basics. Here is a simple checklist. Let us know what you find.


o Spark at a spark plug? (have someone crank the motor while watching spark gap on removed plug). Should be nice and blue spark.
o Do you HEAR the fuel pump turn on for 1 second when the key is turned to RUN. Not start.
o Have you checked fuel pressure at the rail?
o Locate TDC 0 on the harmonic balancer and pull the distributor cap. The rotor MUST be aiming at the #1 sparkplug terminal.
o I'm assuming you have compression of some sort.

Let us know what you find on this list.

Spark, Fuel, Compression is all the engine needs. Something is out of whack.

 

Any ideas on why it wouldnt start at all