I purchased an 2004 D2 with a rebuilt engine several months back. The engine ran well and made good power but had a check engine light with the following codes:

P300 Misfire detection. Multiple cylinders(Emission relevant) Maximum value exceeded. Fault present and intermittent.
P304 Misfire detection Cyl. 4(Emission relevant )Maximum value exceeded. Fault NOT present and static.
P303 Misfire detection Cyl. 3(Emission relevant )Maximum value exceeded. Fault NOT present and static.
P306 Misfire detection Cyl. 6(Emission relevant )Maximum value exceeded. Fault present and intermittent.
P307 Misfire detection Cyl. 7(Emission relevant )Maximum value exceeded. Fault present and intermittent.
P301 Misfire detection Cyl. 1(Emission relevant )Maximum value exceeded. Fault NOT present and static.
P308 Misfire detection Cyl. 8(Emission relevant )Maximum value exceeded. Fault present and static.
P302 Misfire detection Cyl. 7(Emission relevant )Maximum value exceeded. Fault present and static.

After doing a ton of research it seemed like it needed plugs, wires or coils. I have done or had a shop do the following work (in order) to try and fix the issues:

-Replaced both coils (with genuine Bosch coils)
-Replaced spark plugs (3 times. Tried NGK then Bosch +4 now back to NGK)
-Replaced plug wires with Kingsborne 8mm wires
-Replaced all 4 oxygen sensors(with genuine Bosch sensors)
-Replaces crankshaft position sensor (with genuine Bosch sensor)
-Removed K&N filter, cleaned housing and replaced with stock paper filter
-Replaced MAF sensor (with genuine Bosch sensor)
-Smoke tested intake for vacuum leaks (no leaks found)
-Compession test (all cylinders at 165 to 175)
-Tried 2 additional ECUs (no change)
-Replaced fuel pump
-Reconditioned and flow tested the fuel injectors
-New catalytic converters(they were in bad shape anyway)

The codes were reset after each step but returned. The P300 code has been present each time. The individual cylinder codes vary with at least five every time. I drove over 500 miles one time and 200 another (including the various drive cycles numerous times) in an effort to complete the drive monitors. 7 out of 8 monitors completed but not the catalyst. Then the check engine light returned. The truck has been at 2 Rover specialists here in the Los Angeles area recommended by the local Rover club without any solutions.

I can't get it smogged so I can't get it registered. The only suggested idea(from a third shop) that I have not yet done is replacing the engine wiring harness. This idea seems like it would be very difficult and is just a long shot at best. Thoughts?

Other than the harness idea, any other suggestions? I am extremely frustrated and out of ideas. Thanks in advance!

 

I feel your pain as I was dealing with similar **** recently. What were the results from the compression test you did on the cylinders? Make sure there is no dielectric grease on the connectors inside the ignition wires or on the contact areas of the spark plugs as they will reduce current and can potentially cause misfiring. The grease should only be used on the ceramic portion of the spark plugs. Clean all the ports with q-tips and a clean micro fiber rag.

Make sure that all the ignition wires are plugged in firmly. The wires will fit over the pegs easily and generally will push down into place with no issues BUT if you dont hear/feel a little "click" than the wire probably is not plugged in correctly. I played arouned with those dam wires several times before realizing this. Better to remove the intake manifold plenum when fitting the wires. Start with the bottom row first than do the top after. Also make sure none of the ignition wires are to tight. A detail that I missed when I replaced my wires, but each ignition wire is a different length. I fitted some of the wires incorrectly and consequently one wire was so tight it popped off while I was driving! The best way out what length wire goes where is to look at a diagram and use your best judgement to determine which length wires should go where. Also make sure you have the wires installed on the correct ports. There are afew different diagrams floating around the web that show you the correct placement of each wire, however some diagrams assume you are standing in front of the truck looking in while other diagrams are assuming your inside the truck looking forward. Below is the diagram that best helped me.



As the description says... this assumes your sitting inside the cabin of the vehicle, looking forward through the firewall.

cylinder 2, 3, 4 and 7 would be on the bottom row. While 8, 5, 6 and 1 would be the top row.


Best of luck to you mate. Feel free to check out the last several pages on my build thread where I was diagnosing my multiple misfire codes. Many people offered their thoughts so you may find something useful.

 

The last one of these ridiculous intermittent misfire nightmares I had to deal with, I found that power was dropping in and out on one of the ECU fuses due to a bad ignition switch.
I had to hold a test light on the fuse while another guy jiggled the key in the ignition. Unfortunately, we had already replaced the crank position sensor because it was giving really whacked out rpm readings.
I'm not saying this is your problem. Just something to check.
Good luck.

 

I've heard that the interior fuse box sends the 12v to the coils and if the fuse box has been damaged from leaking sunroof drains or has just gone bad it can cause misfire faults because it isn't sending the full voltage to the coils.

 

That sounds like a possibility. I think some checks at the fuse box would be a good idea. You may even have to remove it and really give it a close look.

 

2 bolts at the bottom of coil pack assembly and 2 at the top with SAI pipe secured. Make sure that all of the bolts are in place and torqued down tight. If the coil packs are loose then it will cause misfires.

 

I'd add to what Chubbs said to be sure that the ground wires from the injector harness (bright green, in in each side of coil) are grounded to the intake using the bolts for the coils.

You have replaced alot of stuff! When you get this figured out I bet your rover gives you a break for awhile.

Replacing the wiring harness is not really such a big deal, if it comes to it (but I'd try other things suggested first). The first time I replaced my engine I was not careful with the harness and ended up with crazy misfires just like yours. I still don't know the precise reason, but when I replaced the harness they went away.

I have to re read but have you made sure the ground strap is connected?

Also, on the smoke test, it is really difficult to find leaks under the upper intake, which would be at the plenum gasket or the injectors. I find it hard to believe that all of the injector o rings could all be bad at once but if they were removed and replaced without new o rings then that could be an issue.

How does it run? I assume it is actually running and doesnt feel like everything is misfiring at once. You said it pulled strong. Does the exhaust smell strongly of gas? Does the oil smell like gas? If not as to both you might try disconnecting the MAF. I know yours is new but if the engine doesn't change when the MAF is disconnected I'd suspect it or the wires. You can drive it without the MAF but it will be sluggish and I wouldn't do it for more than a few miles. If yours doesn't seem more sluggish than with the MAF plugged in that's your culprit. Also, try disconnecting the electrical connector to the purge valve and blowing into that pipe. Does the engine change when you remove the connector?

You have something going on that is affecting all cylinders. So I wouldn't be concerned about individual coils, cylinders, plugs, or wires. It is something global. Almost surely something electrical/electronic.

 

Thanks for the tips. I have checked your build thread and there is some great information. I am confident the coils and plug wires are installed correctly

Very interesting. I will definitely give this a look.

Thanks. This a another thing I will check out.

Those bolts are a nightmare but I was sure to get them installed tightly.

The car seems to run fine. The shops who have looked at it agree. No gas smell from the exhaust. The ground straps will get another look. I will check into the MAF and the purge valve. I am also thinking it is electrical. Thanks for the suggestions.


Thanks for all the replies and suggestions. Hopefully I get this figured out soon so I can get this truck registered and start having some fun.

 

So far for me and my 30+ something cars it's always boiled down to something electrical vs mechanical.

One of my 05 Jeep Wranglers spent almost 2 months at the Jeep dealership as they sat there and scratched their heads. They just started throwing parts at it, tearing my perfectly good transmission apart (with only 18K on it), new wiring harnesses, solenoid packs, Torque Convertor, firmware updates, and all the while I explained to them after it would jump into limp home mode a simple battery disconnect PCM reset would solve the problem for at least 500 miles. Well after a full tank of gas (they never replaced), and nearly 2 months without a loaner car, or rental car they called to say they fixed it.

I went to pick it up, drove it 2 miles and it did it again!!!!! This time they finally listened to me and replaced the PCM (that also had the TCM integrated into it for the first year) and that problem went away. Then of coarse I had a leaky transmission pan (their fault), cracked flex plate (once again their fault), and multiple other issues after that which they inflected into my Jeep.

Good luck with your search and keep us up to date!

 

Update: I have re-checked the ground connections and they seem fine. Fuse box looks OK. Since it was inexpensive I replaced the purge valve. If I unplug the MAF the truck quits immediately. I drove 95 miles over the last few days and last night the check engine light came back. Codes are P300, P303, P304, P306, P307, P308 and P93.

Any additional ideas?