Anybody got any feeback on this post from "protozee"???? (Link included, but text is below also)
http://www.automotiveforums.com/vbul...ht=fuel+filter
The jeep shake or shudder, misfire may occur when the vehicle is operated between 50 - 70 MPH
I tried 2 jeep dealers and they could not fix this, one said it was the coil, replaced it no help, and tune up, injectors cleaned too no help. The other on said it was the torque converter and pump it was under warranty, no help. So I think they just want to sell you something or they don’t know any more then we do, or maybe they throw the service bulletins away. So I did some research on the internet and this is what I found the trouble. So far
I have paid a lot of money at the dealers.
Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.
So I bought a 16 oz. bottle of Marvel Mystery Oil, put half in the gas tank and the other half in the oil. No more jeep shake or shudder or misfires.
By the way the $500 at the dealer for decarburizing
4.0L MULTIPLE CYLINDER MISFIRE
Date: 08/01/03
Model Year(s): 1999-2004
Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.
Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).
If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC?s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in ?Limp-In? mode.
The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.
This condition may occur when the engine is not allowed to run at engine RPM?s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM?s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.