[Grobby1]

So I have a 4.0L motor. We replaced plugs, wires, distrubtor cap, and rotor. Well we you start it, the motor runs really rough! So we pulled off each spark plug wire indivdually and put it back on to make sure they were seated correctly. We pulled the distrobtor cap off and made sure the rotor was ok. Finally thinking that I mixed up the firing order on the cap we verified that as well. So everything seems to be correct however it runs rough. Any ideas please help!!!!!

[turtlerace]

What type of plugs did you use?

[Grobby1]

Bosch Platinum+2

[turtlerace]

Put your old plugs back in and see if it still runs rough.

[99Greenmachine]

Originally Posted by turtlerace

Put your old plugs back in and see if it still runs rough.

X2 you need to use old school champion plugs.

Also, what gap did you use on the plugs???

[Fire-XJ]

Did you disconnect the battery while you were doing the tune-up? If not, try disconnecting the battery for 30 mins to clear out the computer. Then reconnect the battery and drive the vehicle around for 15 mins so the computer can re-learn the engine parameters.

[D-BOI]

same thing happened to me when i disconnected my battery all i had to do was drive it around for a few miles and the computer re learned everything but bosch platinum are a bad idea go with regular champion plugs those are the best ones and theyre only 1.99 a piece

[crosschecker]

Check to make sure you didn't swap a couple of plug wires.

[xjfever]

The 4.0 doesn't respond well to platinum plugs, I would replace them asap with champion 4412's and check the gap on each plug before installing.

[teenwolf1393]

if you have a 2000 xj with the 4.0 do not use platinum plugs. just used them and the truck has a horrible idle, before it ran better. and he was running the same plugs after 75k. the factory plugs are Champion RC12ECC(code on plug) and theyre only $2 a pop

[XJH-007]

(it's not a 2000 XJ if it has plug wires and rotor)

I've used the Plat Truck plugs and the Plat4's with no issues.....

But you can try to reuse the old ones just to check. Double check your GAP.

And triple check your firing order.

You didn't loosen the distributor or anything right?

[LobstahJeep]

If he used platinums, they wouldn't need to be gapped. The platinums usually come gapped from the factory.
I agree though, regular plugs are better for the Jeeps.

[_litz]

The run-of-the-mill Champion copper plugs I used on my '97 (from NAPA) were sold as pregapped, and when checked actually were correctly gapped, so it's possible to buy "standard" plugs pregapped.

I'd still double check them, though.

The ones I pulled out had not been replaced in a long, long, long time (haven't really had the $$$, was waiting for the motor to start running rough; never happend - got tired of the sucky gas mileage) and had opened up to over .060 in gap ... motor still ran OK though. Just ate gas and didn't have much power.

I didn't disconnect anything when I did mine ... it fired right up, was happy as a clam.

- _litz