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Desert Destroyer
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Discussion Starter · #1 ·
I'v been reading historical threads on this topic, but couldn't quite find my situation. I'll be as light on the words as possible.

Purchased 03' Disco II in October.
1st week, CEL on. Codes for O2 sensors. Replaced all 4.
Found a radiator seam leak & had this replaced at the shop.
Ran good for a few weeks.
Thursday noticed rough idle.
Friday CEL on & flashing intermittently when accelerating. Goes solid after getting up to speed (40-ish MPH). Took to shop. Spark plugs replaced (misfire code and foul looking plugs...wires appear new).
Shop predicted problem might not be fixed due to idle still being rough & suggested the coil packs might be next if the problem returns.
After about 50 miles, CEL back on/flashing intermittently as before.
Checked codes & have Cyl #1 misfire.

I'm not an auto mechanic, but am an aircraft mechanic and aerospace engineer...I have a feeling this isn't an electrical issue...I'm not aware of how long the O2 sensors were in need of replacement, but I'm betting they were original based on the looks of them. I'm guessing that my rover could have been running with faulty O2 sensors = insufficient fuel/air mixture for some time before I bought it. I'm leaning towards either gummed up injector or even catalytic converter clogging as the source causing the misfire. The exhaust smells rich and has a black soot at the end of the tail pipe...no smoke of speak of.

I cleaned the throttle body. MAF sensor was replaced by the dealer I bought it from. I put some injector cleaner in with the gas & drove it around for 10 min. I also found a new product that is intended to remove build up in the catalytic converter that has some pretty rave reviews that I will put in when I get the tank down to around 5 gal. (per directions on the bottle).

I feel confident this is not something more serious like coolant breach, etc. based on what I see up to this point.

I've got 2 questions:

1. Does what I think might be the problem make sense to anyone? Anything I should be considering that I'm not? (well, 3 questions I guess.)
2. If these systems cleaning attempts don't do the trick, any suggestions?

This truck is in excellent shape & was dealer maintained throughout the years. I think all this is just an age thing & want to get her running like a champ asap. (116K mi.)

Thanks in advance for any suggestions!
 

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You can either throw parts at it or take it to someone that has a proper scanner that can read the Rover's live data streams. If you have an injector problem, you can look at cylinder contribution. If you have a cat efficiency problem, you can look at O2 sensor output pre and post cat. In many cases, the codes are just telling you that something is out of parameter. It could be something entirely unrelated causing it. At the same time, there are some common failure areas and related codes that can be fairly easy to diagnose on-line.

I wouldn't assume that the wires are good. If you're planning on keeping it, I would replace the coil packs and the wires- and use something like the magnecor or one of the others suggested here. It's more likely that a hard misfire is coming from there than the injectors. If you're pulling the upper manifold to replace wires and the coils, you might as well pop out the injectors and service them. You can get a kit from Mr. Injector for $20 with the orings and screens. Buy one of the Harbor Freight ultrasonic cleaners for $30 and let them brew in it overnight. Mr. Injector charges $140 to do it for you but you have about a week turnaround.

before I did anything else, I would do a compression test. I purchased an '04 earlier this summer that ran OK and didn't have more than 80PSI in any cylinder. I don't know if this is true, but I think the Rover eats rings when they overheat. When I pulled that engine, the bores were perfect and the pistons in spec with no scuffing. And this was a 110K/mi one-owner truck with every receipt and a maintenance log. Had head gaskets done 20K previous. Why toss a ton of effort and $$ into it if the bottom end is soft? When you do the compression test, take the hose out of the tester case the day before and warm it up- get the bend out of it. It's very difficult to get it in the two center holes with the SAI in the way. Fighting the hose makes it way more challenging.
 

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Desert Destroyer
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Discussion Starter · #5 ·
Thanks for the insight...I do plan to take it back to the shop since they "fixed" it already. I'd bet they have the equipment to check out the pre/post cat values. Hell, maybe it will turn out to be something as simple as a dud replacement spark plug.
 

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In 2015 forum member Plov had a P0301 and P1319 problem and reported this:

So I finally got to the bottom of this misfire and thought I would share my solution. Don't want anyone else to go through it.
The problem was finally fixed when i replaced the Cats. I know logically it makes sense in hindsight, blocked Cat increased back pressure and slowed engine due to greater pumping losses. I was not high on my list of areas to look given the fault code. With new cats installed I have done 3000 miles without the check engine light coming back.
 

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X2 on what CT090 wrote.
I'm not a fan of speculation as opposed to proper testing and diagnosis.
Just because a guy had a 301 a couple years ago and it was fixed with new catalysts does not mean anything really. Yes bad O2 sensors could have damaged the cats but at this point nothing makes more sense to me that proper pre /post cat diagnostics
 
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Alot of people (myself included) fall into that "I'm not paying someone else for something I can do myself" thing. It's tough to find someone who knows what they're doing and has the tools, that wants to diagnose for you and then send you off to do the repair yourself. I have thrown some expensive parts at a problem only to end up sending it to a shop and paying to fix something else. At the same time, I've thrown thousands at a vehicle at "qualified" shops (including the dealer) to find out that wasn't the problem. I would also say that at least 50% of the times I've sought professional help, I have been outright lied to about things needing done that had no issue.

But all things being equal, I figure I'm pretty far ahead of the game.

Back to the OP's issue, hard to imagine a plugged cat is causing a hard misfire on just one single cylinder. Or a bad O2 sensor. Or a dirty MAF. Chances are, it's a combination of things.

I'd be hesitant to take it back to the shop that worked on it- sounds like they're guessing with the OP's wallet. "Suggested coil packs..." comment leads me to believe they plan on throwing parts at it until either the problem or the car goes away.
 

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Desert Destroyer
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Discussion Starter · #10 ·
I am going to replace the coil packs & plug wires & see what happens. It can't hurt given the mileage & if I test the old coil packs & find nothing wrong with them...well, I guess I have a spare set.
If that doesn't work...then I'll be on here crying again!
 

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Desert Destroyer
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Discussion Starter · #12 ·
$250 for both coils (Bosch), wires (Bosch), intake plenum gasket, and valve cover gaskets (which I might as well replace since I'll have all the junk off the top anyway)...less than I expected. Hopefully, tearing all that apart isn't as bad as it looks like it will be. Tips, secrets, tricks are welcome.
 

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Desert Destroyer
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Discussion Starter · #14 ·
Update: I replaced coils and wires (along with the plenum and valve cover gaskets since I had to tear it apart) and I no longer have the misfire problem. That is not a job for the weak willed for sure. I couldn't afford the $1400 for labor to have it done, so had to figure it out myself.
I had the exhaust system tested at a smog shop and also need a new R/H catalytic converter. Going to go ahead and replace both since the other one is probably not far behind. BTW...$25 for the test at the smog shop is a helluva lot cheaper than the $160 "diagnostic" fee at the dealer. You basically get the pre & post readings you need to determine whether the cat is doing it's job.
 

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Update: I replaced coils and wires (along with the plenum and valve cover gaskets since I had to tear it apart) and I no longer have the misfire problem. That is not a job for the weak willed for sure. I couldn't afford the $1400 for labor to have it done, so had to figure it out myself.
I had the exhaust system tested at a smog shop and also need a new R/H catalytic converter. Going to go ahead and replace both since the other one is probably not far behind. BTW...$25 for the test at the smog shop is a helluva lot cheaper than the $160 "diagnostic" fee at the dealer. You basically get the pre & post readings you need to determine whether the cat is doing it's job.
Glad to hear that you have resolved your misfire issue. $1400 labour equals 12 - 14 hours in most independent specialty shops I would expect.
Wow that's steep labour (in my opinion)

As for the $25 dollar test. I am unsure what it could entail.

I have been a government licences emissions inspector and certified repair technician since 1999 in Ontario Canada.
There are basically 2 common testing methods (as far as I am aware) 1 - onboard diagnostics and 2 - tailpipe emissions. Both are in place here, dependant on the age and registered gross vehicle weight of the vehicle.

I am not aware of what your state test proceedure is but getting physical pre and post catalyst is likely more involved than what 25 bucks could possibly cover.

Onboard diagnostics based testing of course would give you a readiness monitor(s) check....... Butso would even a basic diagnostic scan tool.
I am interested in an information regarding the type of test performed in Nevada so if anyone can expand on it I would welcome the explanation.
If you indeed do have a bad catalyst you will definitely have catalyst efficiency codes setting (p0420, p0430):nerd
 

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Desert Destroyer
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Discussion Starter · #16 ·
The method used reads the pre and post catalytic converter O2 sensor readings via the truck's onboard computer. It will also tell them any fault codes that have been set recently (within the last hundred miles or so & I understand this exact number is different depending on the vehicles monitoring system). The pre/post O2 sensor readings have to fall within a certain range depending on the state in order to pass the emissions check. Mine would fail miserably if I were getting it done for official purposes. I'm actually a little pissed off about this. I just purchased my truck used from a local Mini Cooper dealer in September. NV allows dealers to accomplish the emissions checks & provide a purchaser with a certification to use for registration. What I'm upset about is that I find it hard to believe the emissions check was fine less than 5K miles ago...and is now crap. I dug a little deeper (Carfax) and found that my truck actually failed emissions in July prior to the previous owner trading it in. In my view, this proves the dealer fudged the check...they can't sell a car here knowing it won't pass an emissions check...meaning they would have to replace the exhaust or source of the problem before selling it. Anyway...another subject I'm looking into what recourse I might have at this point.
Hoping my description of what they did for the check makes sense to you..I'm not an expert on the subject...just describing the way it was described to me.
 
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