The quick answer: Yes I get a low RPM sometimes, and no, the misfire happens all over the place.

Here's the LONG version: Mine is off and on. Sometimes it will idle low and stumble quite a bit; other times it'll run smooth as my 350z. When it is running rough, and experiencing the misfire, it will backfire on acceleration at lower rpms, and will feel like it hits fuel cut at times on the highway. I know for a fact it's running very rich - but I can only assume that it's because it's getting horrible spark. That is an assumption though. What is even more odd, is if I "drive it like I stole it" it runs like a champ. I'm talking really drive it pedal to the metal. If I stomp on it good, letting it run up in the rpms (~4K) before shifting (auto trans), it's awesome. When I drive it light throttle, I get all the fuel puking, crappy running nonsense.

I've noticed something particularly odd as well... if I shift the auto tranny manually, it will jump at 3500 RPM almost as if one of the cylinders kicked in.. And if I'm driving along and it's chugging (kinda having difficulty accelerating), I can push the throttle to the floor JUST before the point it will downshift and it smooths out. Kind of like a valve opens up so it gets the air it needs to stop running rich. I've done absolutely everything recommended here (thanks everyone!) and I'm still getting the specific cylinder misfires, the random misfires, and an O2 sensor fault (replaced all four too...). I can live with it like this, but the odd times when it runs the right way, it's a freakin joy to drive!

 

Well thats what I have kinda, I havent had a backfire yet and it only hapens when idling??

 

I just had the exact same problem except it was on two different cylinders.
I didn't read through your whole thread so I'm just going to throw this at you in the event that it hasn't already been proposed.

Wires and/or coil pack.

I was getting random misfires on 4/7 which were the same coil pack..when I got into the job, I noticed my wires on the even side of my block were ***ked and they were 8MM magnecors!! All of my passenger side wires on the coil end were corroded (2, 4, 6, 8) and MISSING the clips that secure the terminal to the coil pack. Yeah I never thought to check the wires when we swapped them. I had one wire (#4) that was entirely bent over so it wasn't sitting on top of the terminal like it should have. Definitely my fault, but I was told repeatedly "just push them on, it don't matter if they snap."

Anyhow...Why cylinder #7 was misfiring when the odd side of the block had perfect wires, I'm calling coil pack for sure. I called Rover and spoke to them about it and they said coil failure is fairly common. My mechanic buddy also said WHY THE **** did they put the coil pack back there? HEAT fries those things and it's HOT back there.

I replaced the coil on mine and put on crappy Autozone wires because I was in a rush $32...$40 for the intake gasket and $250 for the coil pack. The job really wasn't that bad and now she runs like a champ.

Want to do a quick test to see if this might be your issue?
Go spend $20 and buy some champion plugs. It should take you 15 minutes (maybe more if you're not really fast on these things) to pop out the plugs and put new ones in.

See if your Service Engine Soon light doesn't go out as soon as you put in new plugs. Drive it around and see if it misfires...

I did this and it ran perfect...until the next day...4 and 7 showed back up on the scanner.

I hope this helps

 

Did I read that right so all of that never fixed it?

 

No - he replaced his coil pack.

I did as well, although I just did it for the heck of it. Was out of ideas and went for it. Didn't do crap for mine.

 

I typed up a lengthy response last night, posted pictures and everything but my session must have timed out before I hit submit because everything I spent typing up was lost.

Anyhow. I must have done a poor job at explaining my issue. Similar to yours, cylinders 4 & 7 were mis-firing. Clear the codes and 4 & 7 come back.

The story actually starts about 1.5 years ago when my wife bought her 2001 Disco II. One of the first things that was recommended was:

-Magnecor 8mm
-Bosch Platinum +4 plugs

I was in no mood to remove the intake on this thing so I had my wife snap the magnecors on the back of the coil (I couldn't fit my hands back there...and this was before someone came up with and posted the screwdriver trick). She started on the bottom row of the coil pack and then we did the top row. As she's doing this, some wires are snapping on easily and others don't seem to be snapping on at all. I remember her saying "this wire isn't snapping on." several times.

We finish the job, fire up the truck and it runs awesome! Flash forward to about a month ago, the truck starts throwing the SES light, sometimes it blinks, it stutters, it farts. I finally found some time to take it to my buddy and have the codes read, it came back with cylinders 4&7 as misfiring, cleared the codes and within 5 minutes they are back on. My buddy says "it looks like a coil pack to me. But you should research it." So I took the codes and I stumble upon a post over at LRonly where a guy said the Bosch Platinum +4 plugs are crap and to replace them with Champions.

That night I picked up the champions for $20 and had them installed in about 15 minutes. Fired up the truck and the SES light was out, she was running smoothly. I drove her around the block and there was no sign of hesitation whatsoever. I thought that maybe I got really lucky! $20 vs. replacing the coil pack!?!? Who wouldn't be happy?

My wife drove the truck about 20 miles that night and she said it was running great. The next morning however; when she went to drive it, SES was back on, blinking occasionally, misfiring etc. So I went back to LRonly to say the champions didn't fix it.

Immediately I had Doomsayers coming out of the woodwork saying "HEAD GASKET! HEAD GASKET!" So...I had my buddy run a chemical block test to check for exhaust in the coolant. It came back clean. He pulled the codes again and it's cylinders 4 and 7. Just for laughs I call the local rover dealership and they said COIL PACK FAILURE on the DII is semi-common and they wanted $350 for the pack, $500 for labor = $850 for the job. My mechanic buddy asked "why the **** would they put the coil pack back there? That's like the hottest part of the motor!"

here's where the real story begins
So I bite the bullet, really hoping and praying that the coil pack will fix the problem. I buy the pack for $250 (both sides) figuring it would make more sense to replace both sides at once rather than replace one pack only to have the other one die within a few months. Gasket was $40...$290 parts total.

I get the intake off, which isn't a very big deal to do at all. Don't let anyone scare you about this job...it's just disconnecting a bunch of hoses and crap. The hardest part is getting the 4 coil pack bolts out. You're going to need a universal to do it.

while inspecting my magnecor wires
I notice that ALL wires on the even side of the block (passenger side) are BADLY CORRODED AND MISSING THE SNAP CLIPS THAT SECURE THE WIRE TO THE COIL TERMINAL. My odd-cylinders (drivers side) are PERFECT, no sign of corrosion whatsoever.
Wire #4 was badly bent over, it was probably touching the coil terminal but NOT seated making perfect contact. This probably increased the resistance to the point where the coil pack started to die a slow death. My fault/my wife's fault 100%.


Now, 4 & 7 are on the same coil pack...so it would make sense that the pack was probably taking a crap. YOU are having problems on 1&8 which are two different packs, so it's probably not your coil, it's probably your wires...though anything is possible.

If you are getting RANDOM misfires, that would tell me that they are FIRING sometimes but not all the time. So you've got a sporadic connection, either the plugs, wires or at the coil pack.

recommendations?
You could do like I did and replace your plugs, see if it temporarily fixes your issue, it's possible it fixes your issue all together if you got plugs that are screwed up. Or as someone else mentioned, move the plugs to another cylinder and see if the problem follows the plugs. New plugs are going to offer less resistance on the system and they are going to fire easily, the misfires should go away temporarily.

Next, buy yourself the intake manifold gasket and a universal if you don't have one. Reef off the intake and pull the pack and look for corrosion at the terminal. As you're removing the magnecor wires, you should be able to tell whether they were snapped onto the coil or not. If you have a multimeter you can check the resistance of the wires. It's possible that you man-handled the wires and they were screwed up. Also check for those snap-locks.

If you've got $250 to throw, get a new coil pack and install that while the intake is off.

 

AWSOME man you are on it! BUT I just replaced the head gaskets and the coil looks good and like you said 1,8 dif packs, and the wires are new and are snaped in very well might I add! So it might be plugs and this is where I am at I did replace #1 spark plug and 15 miles still no light but she sounds a little roughf to me and its very random missfire any how?
Now for the bad news one of my snape locks fell off when I was getting the coil seated but I snaped the wires in by the heads!