LedZep1984

Hi all, my jeep started acting funny today. i was parked with the engine idling and when i put it into reverse, the whole car began vibrating. not a very violent vibration, but definitely noticeable. when i accelerated, the vibration would stop. also, it doesn't happen every time i idle. on my way home, the check engine light came on. my initial thoughts are 1) problem in ignition system (spark plugs, wires, etc...) or 2) possible air/fuel delivery problem (doubtful).

Just after i bought it i had to have some head/valve work done thanks to the previous owner who neglected to tell me it had been overheated. I had this work professionally done.

It's a 1996 XJ w/4.0 and just over 100k. Any thoughts or ideas? Thanks.

BlueXJ

First what did the CEL turn out to be? Second you need to describe the symptoms a little better than a "vibration" because that does not tell us much. Could be a low tire or a lost wheel weight or a bent driveshaft....................I could go on and on. Help us help you LedZep!!!!

LedZep1984

thanks for the reply, but it's definitely an engine problem because it goes away when i accelerate. all the problems you mentioned would be amplified by acceleration. there is no way to describe it other than a subtle vibration when the car is idling. i found some similar posts where people suggested a total tune up of the ignition system, so i might try that. i haven't had time to check the CEL code yet, but will do tomorrow.

LedZep1984

Ok, so my fault codes were 12 and 43, which, according to a previous post mean: recent battery disconnect and misfiring cylinder, respectively. I'm planning to R&R the distributor cap, rotor, wires, and spark plugs. I want to upgrade while in the process, any suggestions? Does anyone know anything about the Standard Motor Products company? How about parts recommendations? Is it worth it to upgrade to MSD components? Thanks, Mike

gpXJ

Cracked or broken motor mount would cause the vibration at idle as well...though that wouldn't toss a CEL. Maybe that was just a coincidence? I know in my last Jeep I had a broken motor mount and it would shake a little, then over time it got worse, but once I stepped on the gas it would clear up.

Just another thought...

LedZep1984

For anyone interested, I did an ignition system tune-up and it solved the problem. Parts used:
Standard Motor Products cap (http://www.summitracing.com/parts/SMP-FD169X/)
SMP Rotor (http://www.summitracing.com/parts/SMP-FD316/)
Taylor 8.2mm wires (http://www.summitracing.com/parts/TAY-84049/)
NGK plugs (http://www.summitracing.com/parts/NGK-7252/)

BlueXJ

All those are great replacement parts but the Champion plugs will last longer and make it run smoother JMHO.

95Cherokee

I have the exact same problem, do you have a rattling noise that accompanies your vibration like I do?

I'm thinking it's my crank pulley, when I stand over the engine bay and look straight down at it, I can see a little back and forth play in the pulley, [about 1/8in. maybe]

01LimitedXJ

depending on the year, some xj's actually came from the factory with NGKs. Believe its the newer models with the coil on plug set up.

LedZep1984

Hmm... I don't recall any noises. Not sure about the pulley problem, but good luck!