Hello all

On 6/1 I purchased a 2004 Disco with 143K miles and a partially rebuilt engine. It had several misfire codes, so, like an idiot, I bought it anyway. The buyer claimed the following:

Engine is a 4.0 that came out of a 2002, but now wears the 4.6 heads and Secondary Air system. He had the following done this past January and provided receipts:

reworked heads,
new head gaskets
new camshaft,
new lifters,
new push rods,
new rocker arms,
new timing chain,
new oil pump,
new water pump
new plugs/wires
new O2 sensors
new camshaft sensor

Since I purchased it 25 days ago, I've replaced the MAF, coils, plugs, and wires (Magnacor 8mm). That cleared up all the misfires except #8, which happens at idle and lights the SES light preventing it from passing the Virginia Emissions test.

The car doesn't seem to use any oil or coolant, but I had a compression test done anyway. The numbers are:

1: 225
2: 218
3: 212
4: 215
5: 210
6: 225
7: 225
8: 150 / 225 wet

The book says 167-178 psi is normal. My guess is mine are so high due to the 4.0 block with the 4.6 heads. I hope that doesn't cause any future issues.
As for piston #8, I've always been told if the PSI comes up when you wet it, its the rings. Now I know these old engines are pretty finicky, so I'm wondering if that could be a head gasket issue. If it was valves or injector seal, I would assume wetting it wouldn't make a difference.

I've got about 5 days left to get this thing certified. Any advice is welcome.

Thanks,
Tim in Fairfax, VA

 

Are you sure your gauge is correct? Those numbers look really high. Not 100% but I'm pretty sure 4.0 and 4.6 use the same heads.

Regardless, the difference between wet and dry on #8 looks like bad rings to me.

 

Thanks for responding Red.

I had the test done at a place called British 4x4 in Springfield, VA. I agree, they seem too high.

I took it for a 30 minute drive today and got:

P0300 - multiple misfires
P0304 - misfire cylinder #4
P0308 - misfire cylinder #8
P0327 - engine knock

The misfire on #4 isn't new, but it had disappeared for a while after the new plugs & coils. Given the #4 is in the mix, I'm wondering if this isn't related to compression, but maybe instead fuel. Possibly bad injectors or valve clearance. Back in January during the rebuild the mechanic installed a new cam, lifters and rockers. Thoughts?

 

I had one that did this, you have a problem with the piston/rings in cyl #8 - gonna have to take the heads off again to check it out. If the cylinder is ok you can pull the piston out through the top without pulling hte engine. Might want to do one other cylinder just to double check the ring gaps.

 

Well I added 1/2 a can of Rislone High Mileage Compression Repair (with Ring Seal), and after about 25 miles, the check engine light has gone off. I couldn't believe my eyes, so I hooked up my OBD 2 scanner and....NO CODES!!!!!!!! Hallelujah !

Does anyone know how long the OBD 2 drive cycle is (after code clear) that I have to do before I can take it in for inspection?