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2002-2005 Range Rover MkIII / L322
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Discussion Starter #1
I have been working this for a week now and am completely stumped. Help!!

Our 2004 RR started missing severely and pretty much out of the blue. It is most noticeable when sitting at idle with the transmission in gear, and also when just starting out from a dead stop. It is not bad enough to change the RPM indication when tranny is in park/neutral, but you can hear it in the exhaust. The check engine light does NOT come on unless we accelerate at full throttle, and then it merely flashes and goes out when we back off the throttle.

Here are the diagnostics info:

1). Incident first happened after filling tank. Ran the testbook and the only code is “misfire cylinder 7”. I replaced the ignition coil and spark plug on #7, and cleared the code. There was no change in the misfire. Diagnostics now said “misfire cylinder 2”.

2). At this point, I had to assume I got bad gas, since the misfire was moving from cylinder to cylinder. I called the station, who of course denied any other incidents. Also, we filled our other car at the same pump at the same time...and that one has no issues with the gas. Still, we added Heat gas treatment, ran the tank to the low light and then topped off with good gas, just to be sure.

3). As the tank burned down, the missing slowly got better, but never completely went away. On filling the tank with fresh premium gas, the missing got severe again.

4). At this point we pulled the codes again: “Misfire cylinder 2”. “Multiple cylinder misfire”. But 2 new codes appeared...”DM-TL small leak 1.0mm”, and “fuel system pressure test fail”.

I am stumped. The missing does seem to be related to the amount of fuel in the tank, i.e. full tank worse and low tank better. But I have never known the evap side to cause missing. Does anyone have an idea of where to go from here?
 

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The evap leak on a friends f150 caused very similar symptoms. Not sure what you would do but good to put fuel pressure guage om yhe fuel rail Schrader valve. If you blip the throttle and the guage drops slightly that would show the integral fuel pressure regulator (integral to the fuel filter) is working correctly and if you have 50-55 psi that would be good.food There is some stuff to search for on the evap system. You can borrow a guage from parts suppliers. I cobbled one up from a liquid filled fuel guage and a thread on air valve fitting when the borrowed guage was defective. Just curious if you have long cranks before she fires. Keep us posted.
 

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Discussion Starter #4
I’ll pull the fuel pressure readings this weekend. The engine fires as good as ever on starting, and except for the random “burps” runs fine. I figured if it was fuel pressure related, or dirty filter, it would fall on it’s face at high speeds...but it doesn’t.

I have been studying the “tank leak detection module” section of the rave. I cannot relate how the vapor leak side of the system could cause the missing. Last year we lost our gas cap. The engine ran great with the cap missing, but after a day it triggered the “check engine” light, with a “fuel tank pressure leak” code. No missing.

But, this weekend I’ll try:

1). Fuel rail pressure tests.
2). Vapor system leak check.
3). I’ll pull the fuel trims too...
 

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have you replaced the fuel filter? It can easily flow well intermittently, then junk can move around causing it to fall flat on it's face.
 

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Discussion Starter #6
No, fuel filter will be on the list. It’s lower down since it revs just fine to 6k on acceleration. I figure a clogged filter would flatten out at high load/RPM. I will get to it, though.

Ran the fuel trims. All trims at idle dance around 0% +-3%. The exception is the “LTFT B1”, which sits rock solid on 5.4%. It does not change at all. I am not sure if it is wrong that the other trims dance constantly, or that the long term bank 1 is constant. LTFT bank 2 is 0%.

I am still trying to dig out my fuel pressure gage....more to follow.

Note...as the tank of gas is burning down the missing is, once again, getting less severe.
 

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The evap likely does not open on full throttle as iirc it's based on conditions not to mess up fueling. There is tech info on when evap opens to release excess fuel vapours-possibly is where on yours it opens to air and messes the fuel mixture. The f150 ford did not show any codes when it stumbled and their high end techs were sure it was the throttle body.
 

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Discussion Starter #8
The evap likely does not open on full throttle as iirc it's based on conditions not to mess up fueling. There is tech info on when evap opens to release excess fuel vapours-possibly is where on yours it opens to air and messes the fuel mixture. The f150 ford did not show any codes when it stumbled and their high end techs were sure it was the throttle body.
So you are thinking the evap valve may be malfunctioning?
 

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Discussion Starter #9
We’re on tank #3...and still missing. Interesting thing is I cleared the faults, which did not seem to be pointing me to anything useful, so I could see which faults returned. Now the previous faults are not there after about 100 miles of driving ( and missing). The new fault is:

”ECM self test torque monitor”

I am about ready to give up. I cannot find ANYTHING in the RAV talking about a torque monitor. The description mentions that it is a fault, but says nothing about what it is or causes.
 

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Discussion Starter #10
Well...just to close out the thread:

The problem was that both the #7 and #2 coils went out at the same time. 140k of driving, with not a single coil problem, and 2 went out at one time. All the other faults were just white wash disguising the coils.

I will die a happy man if I can ever explain the root cause of 2 coils failing together and on opposite banks. That eliminates grounds and shorts. The last 3 times I had an indication of 2 bad coils at once, it was entirely bad gas. The only help on the forum was a search that revealed an owner who found that a single missing coil can result in multiple mis-fires. So, it's possible that only the #2 was bad...but I'm not going to experiment to find out.
 

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Well...just to close out the thread:

The problem was that both the #7 and #2 coils went out at the same time. 140k of driving, with not a single coil problem, and 2 went out at one time. All the other faults were just white wash disguising the coils.

I will die a happy man if I can ever explain the root cause of 2 coils failing together and on opposite banks. That eliminates grounds and shorts. The last 3 times I had an indication of 2 bad coils at once, it was entirely bad gas. The only help on the forum was a search that revealed an owner who found that a single missing coil can result in multiple mis-fires. So, it's possible that only the #2 was bad...but I'm not going to experiment to find out.
Happy for you. I will check other coils today i have 2 misfires, flashing mil for 5 months.
Dont forget to check pcv system
 

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I don't know what mileage is on your Rover, but I can testify from personal experience that Texas has a horrific heat load on any engine, especially with the use of A/C. I would expect more coil and plug wire failures as the vehicle ages. Heat takes its toll on ANY component, not just electronic units. Ray
 

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Thanks for letting us know. Did you get the 302 and 307 codes finally to show you the misfires?
 

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Discussion Starter #14
The misfire codes were the only codes that persisted after clearing the codes. Typical to RR’s, the evap and other related codes never re-triggered. The other curious thing is that, even though the car ran like absolute crap at low speeds and idle, the misfires would only show the codes if we floored the car for several seconds. I guess it would not be a British car if it didn’t have it’s quirks!?!

The good news, after changing tires, replacing all the front links, and solving the missing situation...the Rover is now driving and feels like a new car! I may actually take the time to paint it this summer. The roof started to get a funny, dull appearance. After it started, I began to notice that all the 03-05’s have the same paint issue with the roof dulling...no matter how much wax you try to use on it. I guess 19 years is reasonable for the life of a paint job, though!
 

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Discussion Starter #15
Well...another follow up. Yesterday the #4 coil bit the dust. I mentioned to the kid with braces at O Rielly’s How odd it is to get all these coil failures so closely together. He says he sees it a lot, not just with RR’s. He thinks the newer coils are more efficient, so more electrical pressure is transferred to the older coils. The engineer in me says that’s not possible, but the kid may have something. I sure can’t explain how all these coils start failing so close together!?!
 
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