During the recent California rains (Thank you God) parts of my road got a bit flooded (6 - 12 inches tops). Sooo...driving my daughter to school one morning we decided to have a little fun, why not?

All was well until 4 days later when driving on the freeway suddenly felt like losing a bit of power and rough. 5 minutes later or so service engine light came on.

Got codes read and only P0304 came up, twice, misfire on cylinder 4. Replaced spark plug wires & plugs (Kingsborne 8mm & Champion 7070 plugs).

Truck drives better but still a bit rough, service engine light still on & still getting P0304 code.

Mechanic told me need a new coil and to pick up a plenum gasket, too. He said I only need one, not the whole pack. he also said if I bring him the part he will install no labor, as part of the plug & wire installation he did today ♥

My question is, would P0304 also indicate bad coil?? Or should I be getting a code for the coil itself? If so, what is that code?

Much thanks in advance!!

 

Nice mechanic!

I do not believe a coil pack code exists, so the misfire code is indicative of a coil,wire, or plug issue. Since he has eliminated the plug and wire, logic says coil pack.

I had an 04' D2 that was running rough and was throwing misfire codes. Changed wires and plugs. I still drive it around to a friends house for some help, etc and it wasn't overheating. Turned out the head gasket was blown and one of the cylinders was misfiring.

So, if after replacing the coil pack your problem is not solved, it could be more severe.

Where in CA and what is the shops name?

 

In CA only licensed shops will read your codes so i went to Aamco in Escondido because they do it for free and because it is right around the corner from my work. After they told me it read P0304 twice I asked them for an estimate to replace wires & plugs. They gave me $215. I asked if I brought the parts if they would do it for labor only. I brought the Kingsborne wires & plugs (Kingsborne is just a town over so I went & picked up direct from them on my lunch break - very nice folks!) and they only charged $100 (an hour labor). Just ordered a coil pack & plenum gasket from Rock Auto, should arrive Monday 12/22. Guess where I'll be on 12/23?

I couldn't believe he said they'd do it as part of today's service. All I could say was MERRY CHRISTMAS.

 

I just noticed you are in HB, so you know only licensed shops can read codes :-)

 

I never heard that. I know you can go to any auto parts store and use their reader.

I have an autologic computer with full Land Rover and Range Rover software, so I don't really need a shop to do it.

If you ever need a remote programmed or your ABS codes read, hit me up. Not to far of a drive.

Good luck, that is really nice of them to do the coils for free. That would take me at least and hour and more like 2 plus. But I'm not a mechanic, I just impersonate one on the weekends!

 

I did not know either until I called a couple parts stores trying to find someone who would read them for me. They all told me they couldn't.

Thanks for the offer!

 

Running rough after a 'water episode' might also suggest your ECU is no longer 'water resistant'. Plenty of stories of corroded casings or failed sealant allowing water onto the circuit boards. You might want to check and make sure the inside of your ECU box is dry.

 

What vehicle are we talking about? I'm assuming D2 because of the plenum gasket.

 

Yes, D2. Replaced both coils. Good to go.