Bmw x5 4.6is rough misfire

[Jason74]

Hi all am Jason and new to this site.
I would really appreciate any help I could get from anyone with regards to an x5 4.6is I just purchased, it's got a really bad misfiring issue and also the previous owner installed lpg onto the car as well, a mechanic plugged it onto his reader and gave me some codes
Here are the codes
P1341
P1343
P1345
P1349
misfire cylinder 1
02 censor 1 heater before cat
Hot film mass air sensor
Misfire cylinder 4
Misfire cylinder 2
Misfire cylinder 5
Now the mechanic is saying he has to change the timing chain and vanos first and if that does not solve the problem then it could be one of the valves and that will require him to open the head, could this really be the problem?
Please I need some advice and if a specialist who know these suv willing to get it sorted out for me I will pay.

[henrym3]

Faulty Spark Plug
Faulty Ignition Coil
Intake vacuum leak
Faulty Camshaft Position Sensor
Ignition Coil harness is open or shorted
Ignition Coil circuit poor electrical connection
That is for P1341 so I assume that these have been looked at by your mechanic. When was the plugs last changed, or coils, but as there is so many my initial bet is air leak. What reason or diagnostics for needing the timing chain changed. What is the mileage

[Jason74]

Thanks for your respond the car has only done a 100000miles so I did not really understand why he is talking about the timing chain and vanos change, and he said if that does not work it has to be the valve that is collapsed ,he dies not really make any sense that's why I thought it's best to ask around

[Jason74]

I have not serviced or done anything to the car yet as I just bought it
Am not sure when the last service was

[henrym3]

100,000 it is quite possible the timing chain GUIDES have gone. That is a very expensive repair. Do you have any mechanical knowledge/experience. Can you do any of the required work yourself. Ie change coil packs and plugs, oil changes, are you willing to spend the money. This is no cheap run a round, even though in the end you would have a brilliant vehicle. These v8’s do not have a history of dropping/burning out valves and none of those fault codes suggest that your vehicle has. But if your mate who is a mechanic says that is possible then he’s either talking bollocks or your not telling us everything. I know you said it’s misfiring but is there any underlaying rattling noise to suggest timing guides are gone.

[Jason74]

He said he thinks the previous owner only drove the car on lpg only and that may have burnt out the valve, he said he did a compression test and these are the result
Bank 1 130
Bank 2 140
Bank 3 135
Bank 4 120
Bank 5 170
Bank 6 180
Bank 7 170
Bank 8 170
I don't really have any mechanical skills but I know what he is planning on doing will cost alot
So I just want to make sure he is not fooling me

[X5Sport]

Get a second opinion, and a diagnostic check done using kit that gives the proper codes rather than generic codes. Either a BMW Dealer (diagnostics take about 30 mins) or somewhere like a Bosch Autocentre as they use the right kit.

Better the spend a little to confirm rather than a lot without good reason.

Coil packs and spark plugs are far cheaper than a timing system rebuild.

Looks like 4 good cylinders and 4 not so good. You have two ‘banks’ of four. No one cylinder is way down compared to those around it though - which I would expect with a valve issue. If all 4 low are on the same bank there could be a common link, which a V8 owner may be able to point at.

[henrym3]

Have you had a drive in the vehicle, are the up/down changes smooth, I only ask as a knackered gearboxes normally end the lives of these vehicles as very few are willing to spend well over half the vehicles worth in repair. Some of those pressures are low but could be down to broken guides and sloppy chain. Some more investigation as to whether piston rings or valves (your mechanic will know how) it’s difficult to make a decision as to whether to fix or forget. You could be looking the wrong side of 3k
If I were to make a suggestion it would be to drop the sump and see if there are any bits of plastic laying in there which tells you the timing chain guides have gone. I that’s good then coil packs and plugs, find he air leaks, see how it runs.
BTW been running solely on LPG for the last 4+ years in my 4.6. You should have 2 reducers fitted to your system as that engine runs well over 300bhp if you haven’t then a burnt valve is possible.

[Jason74]

Thanks again, will take it to a Bosch centre on Monday and just get it checked properly and carry on from there

[henrym3]

Do keep us posted of their views/results.

[Paulpen]

Your mechanic sounds like he does not know whats wrong with it so is having a guess at your expense !

Like others have said you need someone who knows what they are doing not a guess / parts cannon

Did you buy it knowing about the misfire ? Maybe the previous owner kbew it would be an expenise fix and thats why it was sold ?

[IanP]

I had the engine apart on my higher milage 4.6 which had run about 40000 miles on gas, and the valves were fine.
At that time though they certainly benefited from reaseating.
You would certainly know if the tensioners had gone, it's a very common problem on 4.6 engines.
I wouldn't be surprised however if your engine being slightly 'tired' isn't having an effect on the injection settings, an in depth diagnostic is the only way to go.

[Jason74]

Thanks guys for all your input,I will give you the update tomorrow what happens at the Bosch centre,fingers crossed they don't have to open the head