P0313
P0300
P0303
P0301
P0340

These are the codes my truck is giving me. What do you think is going on? I always use 93. I have new platinum 4s and new wires, new fuel filter/airfilter. I have sanded and greased all ground connections. Its a 96 Discovery SD

 

So... why is the head gasket the next thing on your list? If you are leaking coolant, it could cause it. See if your cats are rattly. Plugged cats could do it.

Does it run rough constantly, or just sporadically? Did you get the codes before the plugs and wires, or just after?

 

Sorry for the delay in reply, well lets see here... when I got the truck it already had the CELonI changed plugs wires fuel filter air filter did ATF flush checked and cleaned ALL sensor connections and grounds, cleaned IAC etc. When I went to autozone a while back they said that I had about ten codes stored in it. Because I did all that stuff to it I wanted to erase the codes and start fresh because the cel had been on when I got the truck. These codes that I listed are after I had done all that stuff to it so I guess you could say that they are...updated codes. Truck runs good but sometimes misses and runs like crap. Yes I have a leak from the drivers side back of the head that is persistent and I look forward to replacing the head gaskets and getting a valve job. I didnt know that a leaking head gasket could throw those codes, thank you.

 

I would check for vacuum leaks as well.

 

Are these codes since you did a tune up, how's plug wires did you use?

 

Yes these are codes since tune up Discomike. Tacomatech, its funny you mention the vacuum issue. I have an unused nipple on the charcoal canister that pulls vacuum if I plug it with my finger while the engine is on. I was told it was supposed to be open by someone on this forum so I just left it alone. I wonder if that could be an issue? Discomike I used bosch 8mm wires, I didnt spring for the magnacores that you recommend on this forum. I would say its only been 2 mos since the tune up and I have barely driven 300miles because of the intermittent issue and the fact that we have two other cars.

Thanks!

 

Your 340 is a cam shaft sensor malfunction, sure could be a player in this but not to the point of giving you specific misfire codes.
Try switching plugs from #'s 1 and 3 to other cylinders and see if the codes change to the new cylinders.
Try going out when it is dark, start the engine with the hood up, wet down the plug wires and shake them with a stick to see if they short to the engine.