2002 Disco II with 135K. Previous owner did the HG at 130K. Getting a p0305 error code. Have replaced all the plugs, and plug wires with STI 8mm. Also the coil pack. Starts and idles good. When I accelerate, it throws the p0305 code and I get a loud knock coming from the engine. It sounds like a diesel. Where do I go next? Or do I cut my losses and sell it?

 

Double check the wiring a knock sounds like a backfire. Swap the wire side to side and see if the miss follows its possible you got a bad wire. Can also try the same with the plug.

 

Do a compression test. If there is a leak from the gasket around 5 there will be a loss of compression and a loud tick from that spot.

 

I agree, you need to do a compression test to rule out bad valves. When doing the test, pull the fuel pump fuse, remove all the plugs at the same time and make sure you crack open your t/body.
Let us know what you find.

 

Maybe put in Synthetic oil to try to clean out gunk from the valve train.

Or use conventional OIL and put in some cleaner into the oil to try to loosen the valve from sticking.

May also be prudent to replace that wire and spark plug and see how it goes.

 

Had this problem before changing plugs, wires, and coil pack. Same code before and after so i think i can eliminate any of those. So I will try the compression test. Disco Mike, you said to check for bad valves. Are you thinking possibly a valve sticking open? What are the possible causes of this? Just trying to see what I might possibly getting myself into. BTW, I'm in an area with a forcasted 4-7" of snow tomorrow. GREAT time for the Rover to break down. Lol.

 

Basically it is the same job as you just did only the cost of the machine work will increase to a valve job instead of just truing the heads.

 

Probably won't get to the compression test till this weekend. However, was messing around with it and reset the codes. Start up and idle, no noise, no codes. Rev the engine in park to 2500 rpm's and hold, no noise, no codes. Put it in drive for a short test drive, starts making the noise, and P0300, P0305 come back. Thoughts?

 

I think your gonna find low compression in 5. Do wet test or leakdown to determine if its the bottom end. If it is, it may change your outlook on this job. If its not, head gaskets are not too bad on these cars.

 

Finally got to do a compression test. All cylinders 165-170 except 5. It was about 30 psi. So, am I looking at a stuck valve? Or something worse?