I have a 1998 GZMC Jimmy. Recently it started to rattle but only upon acceleration and driveing. Today however, it has began to vibrate badly. The whole truck vibrates. You can feel the vibration hen accelerating, driving and when in park. I'm really nervouse because this is my only mode of transportation and I have little money to fix. It is a 4wd.
HELP!! My 1998 GMC Jimmy is badly vibrating!!!!!?
- Thread starter myarene99
- Start date
Molson02536
New member
It sounds like you may be in need of a major tune up, Spark plugs and wire set, rotor and cap, and fuel filter will need to be replaced. Also cleaning out the throttle body and replacing the air filter will help.
The rattling you described could be the timing chain rattling upon acceleration or your timing jumped from a worn distributor gear. The other case would be a bad knock sensor that has failed which can cause your issues.
This engine has 1 knock sensor at the rear of the block just below the distributor i believe, but if you go to the dealer with your vin number to your jimmy. They can look it up for you to pin point where the knock sensor is, on some 4.3 vortec, there were on the drivers side on the engine block.
Severe burning on the leading side of the electrodes in the cap, would indicates that the timing is consistantly to far advanced. This engine has a fixed distributor and no mechanical advance. This means that when the PCM varies the timing, the spark must jump a larger gap depending on where the rotor is at the firing time.
Because of the consistant heavy wear on the leading side of the electrodes, this would indicate that spark is firing BEFORE the rotor reaches the electrode. According to my understanding, the knock sensor RETARDS the timing as much as 30 degrees which would bring the rotor closer to the electrode and thus less cross firing. That may suggest that with a faulty knock sensor on the engine would maximum advance is attained, and the spark might actually be hitting the cylinder electrode that just fired again or even another cylinder.
This would produce the engine stubble you are experiancing, and really mess up the o2 sensors if it's on the other bank. Now, if the rotor too far past the intended electrode, you might fire the spark at the next cylinder in the firing order, creating pre-ignition. This seems to be what was happening to you with your Jimmy.
The other issues you may have would be a failing fuel injector system. Here is a link that may interest you. http://members.shaw.ca/betterthanyoutoo/Sticking Poppet.htm
Regardless, if there is a Auto Zone or Parts Source. Have then scan your jimmy for DTC codes and hope there is a code in your history that would lead us to your Jimmy's issues. Good luck and keep me posted.
