I've had a terrible time with my 'new'engine. I bought a 2003 Disco with 4.6. It has a bad head gasket (exhaust leak). I took the engine to a shop. They checked the block, planed the deck, planed the heads, seated the valves, turned the crank, put new cam bearings in, and honed the cylinders. I put new oversized bearings in. New gaskets and seals, etc. New rings. New cam (crower 229) new lifters. Push rods looked good so I used the old ones.

First time I started it, an injector locked open. End result was watered gas, bent rod, destroyed piston.

Back to the engine shop. Cylinders and crank were fine. I replaced bearings, piston, and piston rings.

Reinstalled it. The oil light came on so I shut it off immediately. Before it did I was getting 2, 4 and 7 misfires. I found that metal from the piston got past the screen and scored the oil pump and front cover. Took that out and put a new one on. Checked everything else, all good. When I say took that out, I mean the whole engine. And replaced the front cover and oil pump. I cleaned out the engine.

Reinstalled. Oil pressure is good.

But I still have misfires on 2, 4 and 7.

I should add that between these repairs I used my old 4.0. The 4.0 was in the truck Saturday. It worked fine. I am using the same plugs, coils, and injectors as I used in the 4.0. Yet I have those misfires. So it is something with this 4.6 engine.

I'm really stumped. I give misfire advice all of the time but I don't know what the issue could be. Valves? Rockers? Pushrods? Crower cam?

Forum take the wheel! Help!

Best,

Charlie V

 

No misfire expert but my 2cents:
Timing?
Fuel rail/ injectors/electrical connectors?
Also read bad MAF sometimes.

 

First thing I was going to ask was timing as well. Granted, you seem like you would've checked it

 

Jamie, I appreciate you reading and responding.

Maybe this will help (and maybe not):

When I swapped this time from my good running 4.0 I swapped (from the 4.0) the fuel rail, injectors, coils, oil pressure sender, plugs, knock sensors, cam sensor, MAF (breather hose just swapped over... Kept inside the house while I was swapping rhe engine), wires, pulleys, exhaust manifold, and flex plate. And various bolts and nuts that I didn't want to hunt. The spark plugs had maybe a thousand miles on them and came from the 4.0. I ALMOST went to the store to get new coils and plugs but I stopped... They were working in my other engine two days ago! And in the same cylinders!

Everything else was on the 4.6 already... Heads, lower intake, cam crank, etc. It had maybe 10 minutes run time outside of the shop. Total. I will say that I think the heads on this engine are soft, if that may he relevant. I had to helicoil four bolt holes on the heads and I've never had to do that in my entire life, even working with other sets of land rover heads. But the helicoil worked and I torque everything to spec, in order.

There was no pressure in the crank case when I idled it (or, at least, none coming out of the dipstick tube.

And I'll admit it. Yeah, here to goes. I left one part off so while I had the plugs out and fuel pump relay off and was priming the oil I heard a loud splash and oil was pouring out where I'd forgotten to put the oil filter on. Ha hahahahaha! Okay that's fine. I'd squirted oil in the cylinders and at least Iknew the pump was working. Quickly fixed. So that's my oil pump test.

I'm really confused here. The problem is I don't know anything about engines that I have not personally fixed. That's why I was careful to swap everything that I could without burning gaskets... All of those things were on a good running engine. So Im thinking it is not an electrical problem (though I am open to anything). . The same parts that gave good spark and good fuel to the 4.0 two days ago are on the 4.6, and it is having rhe exact same problem as before. In my mind that points to a problem with the block, the heads, the cylinders, the rings, the valves, or the rockers. Aside from replacing bolts, bearings, gaskets, and rings, and paying people to hone cylinders, plane heads and decks, and seat valves, I have no idea what I'm doing.

I'm not a big tester. I have so many spare parts I just swap things out. But maybe someone can suggest a test (or a part) that I should try out.

Or it is possible that this is just a break in thing and adjustment to a different stroke and cam? Maybe the Rings aren't seated yet? If so I'm ready to drive it!

I am getting p0307, p0306, p0304, and p1300. Flashing SES. Honestly, I have driven with one serous misfire in several vehicles including this Rover, and the engine feels a little rumbly but with the codes I have now it doesn't feel like it has 3 misfires that are chewing the cats. The exhaust smells about as gassy as ever (no gas cloud as when my injector stuck open) so maybe this is caused by the oil burning off that I squirted in the cylinders? No... That would affect all cylinders. I'm grasping now.

 

I did replace the timing chain but I am positive that the marks lined up. I rotated it a few times to make sure they came back to the right spot.

 

Did the flex plate get damaged at all? Maybe CPS isn't happy?

 

Okay I hadn't thought of that only because the CPS was new. This flex plate is a replacement because my last one cracked but it is the same flex plate as was in the 4.0. The flywheel was already on the 4.6. I should have swapped the 4.0's CPS and flywheel onto it in keeping with my "put everything I know works on 4.6" strategy. And it is possible that my cam isn't broken in yet.

The flywheel on it has the little weight or whatever on the INSIDE (toward the engine) rather than on the outside as on the 4.0, which I learned means it has a different setup for the flex plate (no spacer).

Abran did you mean flywheel when you said flex plate? I thought the CPS got information from the flywheel.

Should I swap something out? The CPS?

 

Pull the spark plugs. Start simple. How long were they in the 4.0?

 

Are you sure you don't have any bent valves?
Have you done a compression check?

 

I'd definitely do a compression check on all the cylinders. The cam break in wouldn't cause misfires unless the lobes were already rounded. Longer stroke shouldn't cause any issue either, all that does is pulls more air which would still be metered by the MAF. Did you ever double check that you were using the 4.0 MAF housing since you're using the 4.0 computer?

The flywheel and CPS seems like a decent bet too. I'd definitely check that and the compression.