He there,

I finished a head gasket job on my disco 2, and got everything back together and I’m getting an unfortunate CEL p0304 code. I can clear the code and the car will star and idle fine with no CEL, but as soon as I start driving and the rpms get up there, the CEL starts flashing and the truck runs like crap. The code is always a misfire in cylinder 4.

I pulled the spark plug and it looks a tad bit cleaner than the one from cylinder 6, but they are brand new.

I did a quick compression test in cylinder 4 and 6 and got 110 from 4 and 120 from 6. It was done cold unfortunately, but I just wanted to get a quick sense of whether the compression in cylinder 4 was the issue.

I pulled the spark plug wire and tested the spark and it seemed to spark just fine.

I don’t seem to be losing any fluids, and I had a misfire due to low fuel code, and a knock sensor code, but those have not come back since clearing them.

I also had the three amigos due to a shutter valve code, but that also seemed to have fixed itself, for now.

I did replace the fuel injector filters and o-rings, and I did replace the cats with a generic y-pipe, and the front o2 sensors are walker brand, if that matters.

when I ran a scan with my c-reader, it was saying that the misfire codes were emission related if that matters.

If the compression is ok, there is spark, does that mean fuel is the issue? Or could it be the gap on the spark plug or something? I did drop one when installing them, but everything looked ok with the gap.

After all the work I just went through, I would really like this truck to run smoothly now.

 

Check for intake leak? What are the codes?

 

I suspect fuel injector or seal.

while running spray brake cleaner under upper manifold towards #4. If you hear a change it’s a leak in the intake or injector seal.

 

Thanks guys!

The codes I am getting repeatedly are:

p0300 generic misfire
p0304 cylinder 4 misfire

I also got p1319 a few times. The car sat for a while, and I added about 5 litres of gas to get it going (from the lawnmower jerry). I then went down and added a bunch of premium and I haven’t had that code again so far.

And lastly p0327 for the bank 1 knock sensor. That one has not come back since clearing.

the truck can idle a little rough with no codes, but the CEL comes in and flashes immediately when I start driving down the driveway.

I’ll try the brake cleaner truck this afternoon, and I also have some spare injectors I can swap in. Does it sound more like a leak or a clogged injector?

 

Brake cleaner will rulel out leak, then go from there. Also I have had those small plastic rings break off and get stuck in a valve, revved the motor to 4K to "kick it out".

good luck

 

Perfect, I’ll try both of those. What about sea foam, could a dirty tank or intake be the issue?

Im really hoping it isn’t the can lobe.

 

So this all started immediately after your headgaskets?

Personally I would check for an intake leak, whatever method you want... spray brake cleaner, starter fluid or propane or whatever, smoke test it or just see it it holds vacuum well (my preferred method to start). If all ok...I’d switch plugs, wires and coils around as well as swap injectors around and see if the misfire moves to another cylinder. You rule out a bunch of stuff that way and taking the intake off is no big deal. Test to make sure that injector is getting power while you’re in there too

 

Thanks guys!

I have a parts P38 for my Range Rover, so I decided to take all of the injectors and the coil pack off of that one and put it all in the Disco. I also used some reinzosil in the plenum gasket just to be sure it was getting a good deal.

I got it all buttoned up again, cleared the codes and fired it up and it didn’t throw a CEL. I took it for a drive and it had lots of power and no codes. It looks as though I have solved the problem, though whether it was the injectors or the coil pack, or even the plenum gasket leak I do not know. I do know that I didn’t want to do the job a potential three times to replace things one at a time.

I do still have the three amigos and a code for the shutter something, so hats next on the list.

It was a really long time coming for this to be back on the road, thanks for the input people, it helped a lot.

 

Ok, so after a few days the CEL is back

I’m not getting any flashing CELs anymore, but the light did come back.

Here are the codes I’m getting:

p0304 - cylinder 4 misfire
p1319 - misfire at low fuel level
p0327 - knock sensor 1 circuit low bank 1 or single sensor

I have a full tank of premium fluid in it at the moment.

any ideas?

 

Bummer, I hate it when that happens. I had the low fuel code once when I had a persistent misfire (it was a bad coil) so those two are probably related. The knock sensor is odd because it seemed to have happened after doing your head gasket right? Seems like a big coincidence that your knock sensor is bad, I would check the wiring for the sensor real good since it runs right through where you were working (top of the engine right down the front then to the drivers side of the block. Maybe it got nicked or something. In fact check all your wiring under the intake manifold