If you start a thread asking about misfires, prepare to get 12 different answers. Any they would all be correct in diagnosing a misfire, but for someone that is new to the Disco it may be overwhelming.


Do a search on it here, and read-up. 9 times out of 10, whatever fix worked for someone else will not work in your situation, too many variables.


Google "multiple cylinder misfires" and check out the links, read-up.
This is really all about research. Make a list and start with the obvious by checking things visually which usually concerns vacuum leaks. Anything obvious with the lines and hoses around the upper intake, throttle body, brake booster, so on. Follow all the lines and check they are secure in fittings on both ends. Next thing would be to use smoke or brake cleaner. Charlie_V just posted a how-to video on a similar thread yesterday; will be easy to find. After this, and pretty certain its not a vacuum leak, pull up the RAVE (edit: page 451) and find the section on changing coils or HT wires. It will show 4 bolts that secure the coil packs to the motor. You want to make sure all 4 bolts are there, and torqued down well.

http://www.landroverresource.com/doc...hop_Manual.pdf

When I replaced coils, wires, and gaskets it ran great that night and the next morning. that afternoon it had a misfire on 1 cylinder. Went away but right before I got home on the drive from work, light was flashing and codes were mult-cyl misfires. Took me 2 days to figure out, but 2 bolts were not in the coil pack brackets and that was the problem. Somebody else on a thread yesterday said that a mechanic replaced their coils but only put one bolt back in. If there was only 1 or 2 bolts to begin with, I highly doubt they went out of their way to find some extra bolts that would fit and actually re-fit the coil brackets properly. I would seriously check this, won't cost you anything but a few minutes, but they are VERY hard to see; between the back of motor against the firewall, and centered. take the time to do this yourself. you are the only person that you can trust to do something and get it done RIGHT. That garage was throwing parts and your money at the problem, which is BS.

 

Not trying to start a huge debate but you do not need all 4 bolts holding the coil packs. I haven't had the 2 bottom ones in my truck for over 6 years. As long as the coil pack is secure and not moving it's fine. Thats my personal experience anyway.

 

That's the dumbest thing that I have ever heard. And to even go passing along tid-bits like that is senseless.
Put all 4 bolts in. That his experience. In mine, you need them. If 1 works its way loose....then misfires. Who needs that? And then spend 2 weeks trying to diagnose? wtf.


I had only 2 in the last time I put new parts on, because that is with my little brother decided to go with while I was doing something else. Ran fine for about 100 miles and then multiple cylinder misfires leaving work the Monday after I did the engine work. It took me 2 days to track it down, because I assumed the little a**hole would have put it all the bolts in, and just adding the other 2 bolts fixed the problem.


YOU NEED ALL 4 BOLTS, unless your luck is better than the next guys. Like ol' TooFar.

 

Do the coils ground to the engine, thus needing all the bolts they can get?

I'm wondering why securing more securely(!) fixes a misfire. Unless the connection is critical.

I was wondering if there are legs in the idea of relocating the coils to a less dumb *** place. But can't be the first to consider this, so probably not.

Curious, as I realized one of my bolts is missing, but have no misfire issues so didn't break my ***** replacing it.

 

Got a question about gap. What is the proper GAP distance? Also, can you recommend how to find vacuum leaks? Thanks

 

Gap should be .040 if I recall. Vacuum is usually found by inspecting visually all hoses, listening for hisses (maybe use mechanic stethoscope) some use cigar smoke (it gets sucked it).

 

I think the most important step in finding the cause of a misfire, or multiple misfires, is to determine what kind of misfire it is. What I mean is, are you losing spark, fuel, compression (unlikely, but not impossible, with misfires that come and go), etc. Have a look at the fuel trims. If they are going negative, the computer is trying to lean out the mixture, meaning there is too much fuel being sensed by the O2 sensors. If they are positive, the computer is seeing a lean condition and trying to correct it with more fuel.
Good luck.

 

I had a very similar situation this week. We just replaced coils, plugs and all the cables. Look at the codes I got from ultra gauge. The first image was immediately after the fix, the 2nd was after I did the reset or cleared the previous codes. The 1st codes happened when we forgot to install some vacuum hoses and even the electrical connector to the SAI. It runs fine after the tune up exactly how you felt. So what I did was check all the vacuum leak with carb cleaner according to you tube because the misfire was plenty. I, my last resort was to replace the O2 sensor bank 1 which I remember went bad after installing it, a week earlier.
Finally after installing the used O2 sensor back which I know had no fault before replacing them with brand new Bosch, all the fault codes disappeared. I am hoping that I get spared this time. Been driving the truck entire day now with no pending or fault codes. Need this inspected soon.

 

Have you ruled out a vacuum leak? I don't mean to sound critical here, but it seems like you're just throwing parts at this car without diagnosing anything.

 

Truck is running fine again after a few days in the shop. Was advised to throw some BG 44k in the tank to see if its just a case of some clogged injectors..

Im sure they did a vacuum leak test along with the smoke test for the injectors, but i'm not certain. But the thought now is bad/clogged injectors.

It has been dry the past couple of days as well and previously it had been fairly wet, i'm wondering if water is getting somewhere it shouldn't be and shorting a wire? Just a thought, just no idea where to look yet (rover newbie), ill do my best to run down all the wire harnesses and check for exposed wires this weekend.