I hadn't thought of a bad rocker arm shaft before, mostly because the engine is pretty quiet, even for a Rover. My old P38 sounded like it had marbles rolling around in it, particularly when it was sub-zero in January, but it never let me down, and oddly, never gave me a single fault code in two years and 25,000 miles. Difference is, the P38 was owned by a mechanic, and this Disco 2 was almost certainly owned by a negligent woman (ask me how I know!). It's a clean, southern vehicle, but boy is it torturing me so far... In that true Rover owner spirit, though, I shall not give up.

 

Any update?

 

Hey, folks! Sorry for the delay. I was down in Florida on vacation last week, and this virus has obviously thrown things for a bit of a loop everywhere. My mechanic was in and out of the shop, as well, but I did get in touch with him just today.

We left off with rocker arm shafts a few weeks back. I ordered a set of used rocker arm shaft full assemblies off eBay a couple weeks ago. My guy took the valve covers off both sides, said the existing rocker arm shaft assemblies were in good shape, and were actually better than the assemblies I got off eBay. He turned the engine over by hand, looking at the function of the rocker arm assemblies on both sides to compare the non-misfiring cylinders; all looked good. He cleaned up the existing rocker arms and related parts, and buttoned it all back up. Result: I am still getting misfire codes on cylinders 2-4-6-8.

So, I'm thinking it's time to move on to inspecting the PCM next. As always, any advice is appreciated.

 

It has been a while, so I don't remember if you checked the compression values. I would recommend isolating left to right. You can swap oxygen sensors left to right, then injectors. I suppose it could be a plugged cat, but I doubt it. If it was a partially plugged cat I would expect it to run fine at idle and throw codes when under load. If you want to swap ECU to test, but a full set of ECU/BCU/Inst cluster off ebay and test it. If it does solve your problem you can always resell it.

 

I did find this thread, from somewhat recently, which seems to describe a very similar issue, and similar bodge job on the O2 wiring being the cause:

https://landroverforums.com/forum/di...acement-83582/

No misfire is referenced there, but if an ECU goes bad, I suppose that could cause any number of issues.

 

Hey, folks – hope you're all holding up well. Sorry for the long delay; the Rover has not been a priority this past month. But, I had some time to dig into it this week, and made some solid progress.

I did as Extinct suggested and swapped in a donor ECU + BCU from a friend's SAI Disco. BINGO – no more flashing SEL. It still sounded a bit rough, so we're going to take a look at the plugs this weekend, then swap in the donor ECU + BCU again and see if that helps. We're thinking the plugs might be a bit fouled-up, after running with a misfire since we swapped them in. Not a lot of miles added, but worth a look.

Thank you to those who contributed ideas to this thread, and a BIG thank-you to Zuke, who took the time to exchange PMs with me these last couple days . You guys rock.

On another note, I did some running around in my buddy's Disco today (the ECU donor vehicle). He just picked it up – absolutely beautiful Icelandic Blue, and runs like a top. A great example of how rewarding these Rovers can be when they're taken care of!

 

Did you do the instrument cluster as well like some people mentioned, or just the be ecu and bcu? I'm having a very similar issue.

 

Only the ECU and BCU. The cluster is not necessary in order to determine what I needed to; i.e. whether my ECU is causing my misfire issues. The answer seems to be "yes."

You can swap the cluster, if you want, but you can also drive without it, and live with a flashing ODO (it does continue to count miles). That can be corrected with a re-flash, using the right programming equipment.

 

Two steps forward, one step back.

Following up on my post from Friday, we took my original "bad" ECU + BCU out, and swapped them with the "good" ECU + BCU from the donor 2003 SAI Disco. With the bad ECU hooked up, the donor Disco definitely stumbled and hesitated. We thought we had good news, and thought we'd isolated the problem to my bad original ECU.

We took out the plugs on cylinders 2-4-6-8, where we had the original misfire codes, and they were all definitely black and fouled. They are new copper plugs, so we cleaned 'em up and put them back in, with the new SAI ECU + BCU hooked up. Upon startup, it idled and sounded great for a couple minutes with no CEL, then started stumbling (lightly) around 1,500 RPM, and I got a flashing CEL with P0300 on the UG. I took it for a drive around the block to try and isolate a specific cylinder, and got a P0306 on the UG, as well as P0300 and P1300. Back in the garage, the #6 plug looked just fine. We did not clear the codes.

We tested compression on cylinders 4-6-8, and got 160 - 168 - 155, respectively. Replaced cyl #6 plug with a new plug, went around the block again and got flashing CEL with P0300 on the UG again, but did not get P0306 or P1300.

So, hive mind, what do we think?

 

Misfires have four possible causes:

1. Plugs
2. Wires
3. Coils
4.Compression
5. Mixture to rich or lean.

Plus, wires, and coils can be swapped left to right. Compression can be measured. Mixture is indicated by oxygen sensor readings. What of those 5 have you tested? Give us a quick recap.