Misfire on #4 only (2004 D2 4.6)

[ptschram]

so in speaking to a friend of mine who owns an independent LR shop he is not convinced the block is cracked due to the fact that there wasn't coolant pooling in the chamber when we pulled the head.


Anyway my buddy is suggesting this may be as simple as carbon build up on the #4 valve guides which is causing a valve to stick (likely intake) and to go back and check how easily/difficult it is to slide the value up and down. Also to visually inspect the guides. He has seen this be a problem before in that it is only rough on startup and when the heads heat up the valve stops sticking and everything runs fine...

Reaming the valve guides would address..

This guy runs a Rover shop and said that?

You won't find coolant in the cylinders as it is being atomized as it is drawn into the cylinder, then, the high temps further ensure it isn't in liquid form.

Intake valves very rarely stick, Rovers, however, ARE known for sticking exhaust valves.

Aluminium cannot be magnafluxed, but they can be tested with dye penetrant, however, this won't help you any if your leak is fro behind the valve seats. Pressure and vacuum test on the heads WILL however, reveal these types of leaks.

 

[wulfraat]

PT - had the head pressure tested and it was fine.

What do you think re the chances are that this is a sticky valve vs. cracked block causing misfire only on #4?

Seems that I have eliminated most everything else... Should my mechanic be able to tell if the exhaust valve is sticky. I am not sure he bothered to check - when the head was off he had only pulled the intake valve.

I am at my wits end... any recommendations? I am getting ready to flatbed this SOB and send it your way!

 

[wulfraat]

This guy runs a Rover shop and said that?

sorry I misspoke - my buddy was thinking there would be noticeable coolant loss across 500 miles - which is the mileage I put on the truck before it went in... He asked me if the liner was showing any signs of surface rust after it had been sitting for some time - the liner was fine...

He was just saying I should think hard before I condemn the block without having it pulled and pressure tested.

 

[ptschram]

I am at my wits end... any recommendations? I am getting ready to flatbed this SOB and send it your way!

I have only skimmed the post a couple times, I am sure I missed some of what you did.

Have you checked the cam? Not just looked at it, but measured each lobe?

What machine work was done to the heads?

I wouldn't be able to even start on it 'til probably after the first of the year. The waiting list is getting longer, rather than shorter and I have folks who have sent me deposits just to reserve a place on the calendar.

 

[wulfraat]

Have you checked the cam? Not just looked at it, but measured each lobe?

No.

What machine work was done to the heads?

None - only pressure test from what I understand.

I wouldn't be able to even start on it 'til probably after the first of the year. The waiting list is getting longer, rather than shorter and I have folks who have sent me deposits just to reserve a place on the calendar.

holly smokes business is good!

 

[ptschram]

No.




None - only pressure test from what I understand.



holly smokes business is good!

OK, with these truck, it is pretty critical to measure the cam any time the intake is pulled. I got bitten badly once and won't make that mistake again.

I can't understand why one would pull a pair of heads and not have the mating surfaces measured and resurfaced if needed (I have yet to see one-cylinder head- that didn't need to be resurfaced). In your case, someone did you a serious disservice if they removed the cylinder heads and didn't grind the valves while the heads were off, along with measuring, pressure and vacuum testing, and of course, resurfacing if needed.

I am blessed in many ways. It took me 40 years to find something I liked to do and am apparently pretty good at. I really wish I had pursued a mechanical engineering degree rather than chemistry/finance, I'm sure I'd have been happier earlier.

 

[wulfraat]

Yes this shop is being, lets say, less than consultative. Only one head was pulled to check the liner in #4 (because I asked for that) and I asked that the head be pressure tested so they did that at my request as well. If they were being consultative I guess they would have suggested the other come off and a complete head job be performed if needed...

BTW what is retail value for having the heads re-surfaced along with the valve seats, valve guides etc..?

 

[ptschram]

BTW what is retail value for having the heads re-surfaced along with the valve seats, valve guides etc..?

With mark-up, cleaning, pressure testing before anything other than cleaning, measuring mating surface, resurfacing, grinding valves, reassembly, vacuum testing runs $350. I flat rate headjobs on non-SAI trucks at $2K and can't keep the parts in stock as they are so common.

 

[wulfraat]

Thanks so much for the guidance PT

 

[gabriel]

i read this book many many times when i was experiencing the issue http://books.google.com/books?id=gmSavy1RPxEC&printsec=frontcover&dq=How+to+Power+Tune+Rover+V8+Engines+for+Road+and+Track&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&as_brr=0&ei=cHfcSq2GHpKwNtqswJMP#v=onepage&q=&f=false
page 30/31 explained what was going on with my 03. The tech said the liner was loose/slipped but did not drop. After having the tech commute with it for a couple of weeks he was able to spot a tiny bit of coolant in the cylinder. But all the other times the cylinder was dry and did not misfire.

 

[sitchon]

Wulfraat, man, I am sorry to hear that. I don't know what I would do if I were in your shoes. That's a lot of Simoleans.

Maybe try calling Roverland Parts and see what they say. You have an awful lot of good components to offer- they may be able to work with you towards a win-win outcome. At least they have the experience with this sort of thing to talk over scenarios from their previous experience.


Nick

 

[wulfraat]

I did speak with roverland when looking at engine options, I also have a line at a re-built 4.6 short block for a good price...

After speaking with several sources, including my local mechanic - I am just not ready to condemn the block yet.

There was some small amounts of "coolant or oil" in the calender that were picked up via borescope... So it is not 100% for sure coolant. Could be oil from a leaking oil seal on the valve guide... IE pools on the valve when the engine cools then enters the chamber on cold startup.

I am sending the heads to PT for inspection and full head job...

why I am thinking the fluid is likely oil because that the chamber had no indication of "steaming" and there was a solid buildup of white crap on the spark plug itself... I will never know for sure unless the I test the block... could be a number of things, I am just not ready to swap the block especially since the local shop is not certain they can even have the block pressure tested (properly) locally.

I think I am simply going to have the heads re-done, measure the cam lobes and if they are good simply stick it back together an hope that new oil seals and a head job fix the problem. IE hope for the best. $1700 of shop labour and new gaskets at risk... If it doesn't work out them hey lesson learned and I should have wrenched myself...

If it does turn out to be the block then I may simply run the rig down to PT or try to tackle the swap myself or... well.. both! hahaha

 

[No Pvmt]

With all these problems just on this board you would think that LR would da a recall! I am sure there are a lot of other people with the same issues.

 

[jymmiejamz]

With all these problems just on this board you would think that LR would da a recall! I am sure there are a lot of other people with the same issues.

Its not a safety issue, therefore no reason they would do a recall. At most they might do a service bulletin, but that is unlikely since they are almost all out of warranty.

 

[jymmiejamz]

I did speak with roverland when looking at engine options, I also have a line at a re-built 4.6 short block for a good price...

why I am thinking the fluid is likely oil because that the chamber had no indication of "steaming" and there was a solid buildup of white crap on the spark plug itself... I will never know for sure unless the I test the block... could be a number of things, I am just not ready to swap the block especially since the local shop is not certain they can even have the block pressure tested (properly) locally.

If it does turn out to be the block then I may simply run the rig down to PT or try to tackle the swap myself or... well.. both! hahaha

What do you mean by rebuilt? I hear people throwing around the word "rebuild" a lot when they should be saying "reseal."

The block can be pressure tested, but the front cover and both heads need to come off. You need plates to block off all of the openings where coolant flows, so two plates for the front, and four plates for the deck. Put a tire valve stem in one of the plates and pressurize with air. Put some soap around the top edge of the suspected cylinder liner and watch for bubbles. Mine leaked at about 30 psi, but some take up to 100 psi to visibly leak. Then if you want to see the crack take the block to a machine shop and have them machine out the liner and retest, the crack will probably be in the middle of the cylinder and should be pretty obvious with soap and air.

 

[wulfraat]

What do you mean by rebuilt? I hear people throwing around the word "rebuild" a lot when they should be saying "reseal."

well the 4.6 "re-built" short block would be a used block that was pressure tested, a used crankshaft/ pistons/connecting rods that have been re-balanced, new camshaft, new oil rings, new timing chain, etc..

The block can be pressure tested, but the front cover and both heads need to come off. You need plates to block off all of the openings where coolant flows, so two plates for the front, and four plates for the deck. Put a tire valve stem in one of the plates and pressurize with air. Put some soap around the top edge of the suspected cylinder liner and watch for bubbles. Mine leaked at about 30 psi, but some take up to 100 psi to visibly leak. Then if you want to see the crack take the block to a machine shop and have them machine out the liner and retest, the crack will probably be in the middle of the cylinder and should be pretty obvious with soap and air.

Yes this is what I understand the process to be but my dealer does not have the kit to do this and they are saying they would have to pull the block and send it out. BS. I am not going down that path with them especially since I don't know who they are sending it out to. At this stage I think I will take my chances and pop on the heads after the valve job/re-surfacing and if that doesn't work I will work with an independent. I would rather spend the $$$ with someone I trust if I need to pull the block.

 

[adriatic04]

Look on youtube for a rover specific block tester. They even show it in use.

 

[wulfraat]

Update... my local tech told me "valves look OK to me..."... I sent the heads over to PT for inspection/pressure test/valve job/resurfacing/etc...

Turns out the valves are in really bad shape and there is evidence of #4 valves not closing...Lots of carbon buildup on the stems etc..

Engine is going back together once the heads are done (perhaps next week) - hopefully this fixes the #4 misfire issue, cross your fingers.

One way or the other I am never bringing my truck into LR Omaha again.

 

[nathansharkey]

Please keep us posted...

I am having a similar problem on a 2002 4.0L with 55,000 miles on it. No leaks observed on a leak down test. Cylinder #4 Misfire. No evidence of coolant in exhaust. Coolant is disappearing somewhere. No evidence of exhaust in coolant. Rover Overheats when idle, but not while driving highway speeds. Thermostat was replaced and problems still continue.

 

[wulfraat]

Update - heads should be done and will ship back to me in the next couple days. Report back I got today was that #4 valve was definetly sticking due to carbon buildup and there is some confidence that this was likely the issue causing the #4 misfire. The head will go back on next week and that will be the ultimate confirmation that a head job has solve the problem.

Ill let you know how it goes. If you tear down the engine I recommend sending the heads to PT for an expert opinion along with feedback from the machinist he works with.