I had a '92 Dakota 3.9L with a timing belt (at least that's what they told me). It went at 90,000 miles and ruined the engine (for once extended warrany paid off!). I now have a '99 3.9L with 92,000 miles. I just had the catalytic converter and O2 sensor replaced because that's what the code said to do. I'm afraid i may be treating the symptoms rather than the cause. Does a '99 3.9L have a timing belt or chain? Are there any tests i can run or have run to determine if the engine is running right? Before the catalytic converter started rattling I could smell that it was running rich even after it had warmed up. I guess i am concerned that i may have a timing belt issue again. If it has a chain, could it just be getting loose? What would cause that and is there a way to check it without tearing the engine apart?

Thanks

 

Yes there is a timing chain. There is a TSB somewhere on the chain rattling. If you do a search you may find a thread that has it here. I'm not sure though if the timing chain would make it run rich.

 

I too need to replace my timing chain. I got a new one to put in, but just a lack of time to put it in. Yes I know its a poor excuse.