P0300, P0303, & P0304 Codes

[JoeValkIS]

I have a 2000 Sport (4.0L), 5-speed, that randomly gives me the above codes. I have replaced the OPDA, cap and spark plugs but still getting the random codes. Random because one day its fine, drives without throwing a code and others...it throws a code. Usually it is shortly after start-up. Before I spend the money on a new coil pack, what else should I be looking at?

Thanks in advance for any help.

 

[Chris]

Here's a question... when you replaced the OPDA did you reuse the Mopar sensor that came on the original OPDA?

Also, did you replace all the other parts with genuine Mopar parts? I'm asking because it's very, very, very well known that our TJs do not like aftermarket sensors.

 

[Jerry Bransford]

Exactly what brand and model # of spark plugs are installed? The wrong technology spark plugs that would work fine in older 4.0L engines will cause hard to diagnose misfires and idle problems in the newer 4.0L engines with the distributorless coil rail ignition system.

 

[Blade]

Exactly what brand and model # of spark plugs are installed? The wrong technology spark plugs that would work fine in older 4.0L engines will cause hard to diagnose misfires and idle problems in the newer 4.0L engines with the distributorless coil rail ignition system.

Jerry is right on point with the spark plugs, when I did my tune up after I bought it, I put iridium spark plugs. My TJ ran horrible, it misfired and had a weird ticking noise during the test drive. Took them out and put the old copper ones back on and it ran like a champ.

 

[Jerry Bransford]

The right brand and model of iridium plug is a great choice in any of the 4.0L engines including the latest distributorless with coil rails. One 'correct' iridium plug is the Autolite XP985 which I've been running for years. It's a very popular choice which is known to perform well for 200k miles.

The type of technology plugs that don't run well in the newer distributorless engines are single tipped platinum plugs like the Autolite AP985 or Champion 3034. Their problem is the platinum coating is only on one side of the gap. That eventually causes misfires with waste-spark ignition systems like the newer distributorless 4.0 engines use.

Double tipped platinum plugs like the Autolite APP985 and Champion 7034 work fine in the newer 4.0L engine too. These perform well for about 100k miles.

Just avoid the single-tipped platinum plugs like mentioned above.