Cyl 7 misfire continues

[stupidwhitecat]

This is a continuation of the thread I started about a month ago: http://www.discoweb.org/forums/showthread.php?t=66486

Quick synopsis of previous events:

This code has popped up twice in the past 1.5-2 months. First poppped up and I did a general tune up (BTW 105k miles). Air filter, plugs (NGK nothing fancy), cleaned MAF sensor, seafoam, and cleaned throttle body. Also at the time checked out the wires(looked ok to me) I even ran it in the dark looking for any arcing and nothing, ran some seafoam through the intake and gas. Code went away after a couple days. About 1.5-2 months later the code popped up again this week. The engine runs fine, power good, idles a little rough, acceleration is good, runs smooth, avg gas mileage. I always run premium gas, I buy brand name gas. And I always run a fuel system treatment every3-5k miles.

Ok. So after this I decided to replace the plugs (again) and wires. I replaced the NGKs (only ~2500 miles on them) with the champion coppers, and replaced the wires with magnacore 7mm. Now the idle was still rough and it was making a ticking/grinding sound from the front of the engine. Long story short dealership replaced bad A/C compressor, power steering pump, and alternator belt. Now purrs like a kitten. The engine has never idled so quiet or smooth and drives like a dream. About 50 miles of driving after bringing it home from the dealership the CEL pops up, I pull the code and sure enough it is the cyl 7 misfire code. Now it still idles drives fine. I have NO symptoms of a misfire other than the stupid orange light on my dash.

I don't know where to go from here. I assume if it was a coil pack more than just the #7 cyl would be misfiring. My next route is fuel system. I am going to seafoam the sh!t out of this thing. I am going to run a half bottle through the intake and a whole bottle in the gas. If that doesn't do it I am going to drive it until is catastrophically fails. I just spent $1900 last week I am not dumping anymore money into this thing. I am not going to throw money at it trying to diagnose this problem ie: replacing the coils, taking off the head looking at the valves, etc. Especially since it drives fine and I am basically treating a light on my dash board. And the bad news is the dealership got us a rental while it was in the shop. They got us a new Tahoe and my wife loves it. I have not even told her about this problem yet. She already wants to get rid of the disco and get a tahoe now. If this continues it might seal the disco's fate.

 

[stupidwhitecat]

Oh yeah forgot to mention other than the problems above,why I am generally losing my patients with rovers. First off the dealer tells me that the A/C compressor pulley is bad and it is non-servicable. Ok, then he says it will be $1000 for the compressor ONLY. Said hold on a sec. Logged onto atlantic british and find the OEM compressor there brand new $399. Called them back and said "I'll be overnighting you a compressor hold off on ordering that."

Then they tell me that while disassembling the compressor and alternator belt they notice that the power steering pump shaft is "sticking out about 1/2" and "we've seen them go bad and throw the shaft across the engine bay and take out the radiator etc" The best part is that the power steering pump was replaced a little over 2 yrs and 30k miles ago. How in the hell are these part engineered / produced that they last only 30- 50k miles? I've owned 1 honda that had over 200k miles on it, I owned another with 150k, I owned an acura with 120k, and now have a volvo with 115k. I have never needed to replace any of the parts on those cars that I had to replace on the rover. At 50k it had head gaskets, almost every seal in the engine replaced due to leaks, the front engine cover replaced. By 70k it had both rear calipers replaced, numerous pulleys due to bearings, the front drive shaft and the power steering pump. And now at a little over 100k it is on the 3rd power steering pump, new a/c compressor, and it has a repeat misfire code.

Seriously what is the deal? I love rovers but not this much. I have owned this car for 2.5 years and spent more on repairs than I have for all of the other cars I have ever owned COMBINED. And the thing that irks me the most is that I have babied this car. I meticulously maintained this vehicle. Every factory reccomended service was done at the correct intervals and this is the outcome. I was seriously considering trading this in on a range rover at some point but now I am having some serious doubts. Sorry I just had to vent. I really am almost at my wits end with this car though. Which is sad because I do love it.

 

[DeanBrown3D]

....

Then they tell me that while disassembling the compressor and alternator belt they notice that the power steering pump shaft is "sticking out about 1/2" and "we've seen them go bad and throw the shaft across the engine bay and take out the radiator etc" The best part is that the power steering pump was replaced a little over 2 yrs and 30k miles ago. How in the hell are these part engineered / produced that they last only 30- 50k miles? I've owned 1 honda that had over 200k miles on it, I owned another with 150k, I owned an acura with 120k, and now have a volvo with 115k. I have never needed to replace any of the parts on those cars that I had to replace on the rover. At 50k it had head gaskets, almost every seal in the engine replaced due to leaks, the front engine cover replaced. By 70k it had both rear calipers replaced, numerous pulleys due to bearings, the front drive shaft and the power steering pump. And now at a little over 100k it is on the 3rd power steering pump, new a/c compressor, and it has a repeat misfire code.

By any chance are all these repairs at the same dealership? If yes then I would be looking to find a different place asap - I mean even discos aren't that bad.

 

[JohnB]

I don't know where to go from here. I assume if it was a coil pack more than just the #7 cyl would be misfiring. My next route is fuel system. I am going to seafoam the sh!t out of this thing. I am going to run a half bottle through the intake and a whole bottle in the gas. If that doesn't do it I am going to drive it until is catastrophically fails. I just spent $1900 last week I am not dumping anymore money into this thing. I am not going to throw money at it trying to diagnose this problem ie: replacing the coils, taking off the head looking at the valves, etc. Especially since it drives fine and I am basically treating a light on my dash board. And the bad news is the dealership got us a rental while it was in the shop. They got us a new Tahoe and my wife loves it. I have not even told her about this problem yet. She already wants to get rid of the disco and get a tahoe now. If this continues it might seal the disco's fate.

Wow.
Question
Have you done a compression test? Stop throwing parts at this thing until you start taking logical steps.

 

[stupidwhitecat]

By any chance are all these repairs at the same dealership? If yes then I would be looking to find a different place asap - I mean even discos aren't that bad.

Yes, same dealership. I should say that most of the repairs I listed were done under warranty. So I didn't really have an option to take it anywhere else. The only repairs I paid for out of pocket were the front drive shaft and the most recent repairs to the A/C compressor and power steering pump.

Wow.
Question
Have you done a compression test? Stop throwing parts at this thing until you start taking logical steps.

I am taking logical steps. Most common problem with a misfire code is ignition. So I replaced the plugs and wires. The only other part I "threw at it" was an air filter that was due to be replaced anyway. Other that those parts and some cleaning (MAF and throttle body) thats all I've done so far to try and fix this code.

On another note hopefully some good news. I was tooling around the engine bay and looked over the air filter and noticed that the "tech" that tore apart my engine bay didn't re-assemble the air box correctly. The one "tab" toward the front of the box was not seated properly. And because of that there was a gap at the front of the box where you could see directly inside to the filter element. So I have corrected that and am hoping that this may have thrown the code. I also took pictures and will be calling the dealership seeing as though I've been driving around for 100 miles with an open air box. Just to get it on the record in case the MAFS ends up going or something else due to dirt or debrit getting sucked into the engine through the open air filter box.

 

[stupidwhitecat]

Here are a couple pics I snapped. What is the concensus is this a possible cause for the misfire code or not?

http://img.photobucket.com/albums/v471/stupidwhitecat/006.jpg

http://img.photobucket.com/albums/v471/stupidwhitecat/007.jpg

http://img.photobucket.com/albums/v471/stupidwhitecat/004.jpg

 

[DeanBrown3D]

is this a possible cause for the misfire code or not?

Nope.

Did any of the plugs look like they had black shit all over them or different from the others?

Can you post up ALL of the codes here?

 

[stupidwhitecat]

There is only one code: cyl 7 misfire, never had any other codes. Off the top of my head something like P0307. The plugs now have less than 100 miles they look new. The old plugs when I took them out, still looked good, The 7-8 cylinders were "dirtiest" out of all of them. Now again this was the NGKs I had in for maybe 2000 miles before changing over to the champion copper. I actually saved the two not being sure if when I started trying to fix the problem if I would need them or not. I will take pics of them.

 

[stupidwhitecat]

Ok, here are the pics of the plugs I saved (i'm very anal). Keep in mind these were changed out for champion coppers and at the time when I changed them out the had around 2000 miles on them.

Both # 7 and 8

Number 8

Number 7

 

[ptschram]

Narrow the plug gap to the minimum and give it a try.

 

[stupidwhitecat]

Thanks, I'll give that a try. Right now I am using the 322 champions.

 

[stupidwhitecat]

Update: aprox. 400 miles since the code appeared and it remains. Tried the advice of ptschram and gapped each individual plug to the min reccomended spec and the code continues. The only other thing I have done since is I gave it a double dose of seafoam in the gas tank and ran it through, no change. Engine continues to run fine. I've been using it pretty hard past few weeks. Getting the boat out of storage so I have been pulling it to and from my house and storage and to the water and it has been doing fine. Any other reccomendations? I am thinking of running a full can of seafoam through the intake. Other than that I am not planning on taking it to the dealer because I am not prepared to preform any major repairs on the truck. The only reason I am still even trying to fix this is because as you all know it will not pass state inspection with a CEL.

 

[Yadranco]

I had missfire on the 3rd cyl.Mechanic changed all wires and plugs , he said coil packs are ok.He did pressure test of cooling system and it shows that it is slowly loosing pressure when engine is cold and faster when warm.Conclusion , probably head gasket on 3rd cyl is giving up.He said drive it as long as you can but don't over heat the engine and be ready for head gasket job in near future.Right now I am looking for parts for in line thermostat.:victory:

 

[mbrummal]

Conclusion , probably head gasket on 3rd cyl is giving up.

Your mechanic should know the head gasket doesn't seal any coolant passages on cylinders 3,4,5 or 6. If it is leaking into the #3 cylinder, it is probably the block failing.

 

[CandiMan]

I don't know where to go from here. I assume if it was a coil pack more than just the #7 cyl would be misfiring.

Not necessarily. Even though one coil ignites two cylinders, it's possible that a bad coil can only effect one cylinder only. I once had a misfire code (I can't remember which cylinder) and you can definitely tell the engine was missing on one cylinder. I swap the bad coil to another location within the coil pack and the missing cylinder went to another location.

My suggestion, swap #7 coil to another location and see what happens.

Also in my opinion, a air filter box that wasn't properly closed/sealed will not cause the miss fire code.

Being anal is not always a bad thing.

 

[stupidwhitecat]

Your mechanic should know the head gasket doesn't seal any coolant passages on cylinders 3,4,5 or 6. If it is leaking into the #3 cylinder, it is probably the block failing.

After all of the investigating and reading that I have done, this is pretty much the conclusion I have come to. A cracked liner. I may try and swap over the ignition coils at some point since that would be a relatively cheap fix if that was the culprit. For now I just used my reader to clear the code. I wanted to see if it would go away on its own after so many drive cycles. For now it is gone and we'll see how long it take to pop up again. (fingers crossed)

 

[mbrummal]

After all of the investigating and reading that I have done, this is pretty much the conclusion I have come to. A cracked liner. I may try and swap over the ignition coils at some point since that would be a relatively cheap fix if that was the culprit. For now I just used my reader to clear the code. I wanted to see if it would go away on its own after so many drive cycles. For now it is gone and we'll see how long it take to pop up again. (fingers crossed)

you have a cyl. 7 misfire and there is a coolant passage through the head gasket next to the #7 cylinder.It could be the head gaskets. It could also just be the coils or something else. Yadranco said there was a coolant leak and cyl. 3 misfire. That isn't the head gasket.

 

[JohnB]

you have a cyl. 7 misfire and there is a coolant passage through the head gasket next to the #7 cylinder.It could be the head gaskets. It could also just be the coils or something else. Yadranco said there was a coolant leak and cyl. 3 misfire. That isn't the head gasket.

Wouldn't combustion gasses be blowing up hoses if the gasket was breached in that location? Pretty sure on that.

To the OP. Compression test!!!!!!!!!!!!!

 

[mbrummal]

My head gasket 'failed' between cylinder 7 and the coolant passage. It pressurized the coolant system and there was coolant loss but no hoses blew up. I released the residual pressure every so often.

It did start spewing out white smoke like a lot of head gasket failures at one point so it doesn't always just pressurize the coolant system with combustion gasses.

 

[stupidwhitecat]

you have a cyl. 7 misfire and there is a coolant passage through the head gasket next to the #7 cylinder.It could be the head gaskets. It could also just be the coils or something else. Yadranco said there was a coolant leak and cyl. 3 misfire. That isn't the head gasket.

It should not be head gaskets. But with this truck I really don't know anymore. The headgaskets were replaced around 60k miles under warranty. They were done correctly, heads were machined, valve seals, etc. So as it stands right now there are about 50k miles on the "new" head gaskets. And I have NO coolant loss. I've been watching that tank like a hawk.