Hi all,

I have a 2005 Grand Caravan 3.8L. The van started acting up sometime ago specially when trying to accelerate or driving uphill and the check engine came up with P300 code. I replaced the spark plugs and the wires and the code never came back and it was good for about a week but then it started acting up again like before! However, this time with no check engine/codes.

I found a number old threads and webpages with similar problem but with different resolutions from simply replacing a spark plug to changing the manifold gasket or a broken valve spring!

So what are the things that I can check/change to fix/diagnose the problem before needing a real mechanic?

I thought about replacing the ignition coil pack (~$30) but wanted to ask first before wasting money.

 

So exactly how long ago did the poor running start? If enough raw gas gets sent down into the cat as a result of misfiring, it eventually will get trashed out. You could test for a plugged cat by temporarily pulling the upstream O2 sensor to see if it runs better with some of the exhaust going out the O2 sensor port.

 

I would say at least 5 months since it started this. I was aware and worried about the cat but didn't have money to fix. But would a plugged cat effect the car acceleration only? since when on highways (and constant speeds) the car drives smooth and with good MPG.

But I am going to check the O2 sensor and let you know the result.

BTW, using a simple OBD2 reader the cat passes the test and I don't get any error codes.

 

It was a faulty ignition coil, I got one from ebay for ~$30 (mopar) and installed it myself and the car now runs great.