Chrysler Repair/2002 3.7L Liberty Cranks but won't run
I have a 2002 Jeep Liberty, 3.7L with just over 100K miles.
First symptom was rough idle / vibration. That went away and it drove fine. Then a few days later it would crank but not run.
The car will crank, spark, and stutter then die. RPMs bounce and it smells of gas out the tail pipe. It vibrates horribly and sounds like it is missing on one or more cylinders. No codes are being thrown (not by the key trick or my OBDII reader via the Torque app).
CKP (have used OEM part)
Installed new plugs.
After replacing the above I left the battery disconnected for 24+ hours to reset the computer, but it still won't run. Same as before, the car will crank, spark, and stutter then die.
I checked the fuel pressure and with key on it reads 42 psi (picture attached). When cranked it bounces like crazy between 40 and 50 psi.
It will try to run but I have to hold accelerator down and keep RMS over 2000. It smokes out the tail pipe. As soon as I let off the gas it dies.
I'm thinking bad fuel pump or filter, but would like to have a better idea before I have it towed in for repair...
Any help would be appreciated on how to solve this.
When you have the sudden onset of poor running/no starting but no fault codes it means there is something wrong which is not well-monitored by the self-diagnostic capability of the engine. It could be a malfunction of a component which is not so severe as to be 'caught' as fault, or the other item which often causes missing as you described it is the exhaust gas recirculation valve which although monitored somewhat can get gummed up and then fail to close tightly which it has to do to give a proper mixture to start and idle. That will usually not be detected by the self-diagnostic capability.
So I recommend lubricating the stem of the valve and the valve seat. What is shown in the '06 manual which is the only one I have for the 3.7L engine is a more complex system too with air control valve which is described as being 'open' to some extent always.
I haven't worked on such a system nor do the drawings show a close enough view of the egr valve itself to let me know if the valve stem is exposed or hidden away. If the stem were exposed to view you would see a circumferential slot, then you could start by moving the stem back and forth with the tip of a screwdriver to determine if the internal spring-action is closing the valve to a dead stop. If not then I have had success using WD-40 sprayed on the stem where it enters the valve body followed by using the screwdriver to loosen up the action by moving the stem back and forth.
So if you can ID the egr valve and check out that approach it might be all that you need to do solve this.
I can copy about 10 pages from the '06 Liberty manual showing the overall system and how to take it apart. Tell me your email address, but don't use the @ symbol instead use "at", or the address will be erased automatically.