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Matt
Matt, Mechanical Engineer
Category: BMW
Satisfied Customers: 22247
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My 2004 BMW X5 3.0 d has fuel smelling smoke. Had injectors

Resolved Question:

My 2004 BMW X5 3.0 d has fuel smelling smoke. Had injectors done. Still smoke on startup and fuel smell when running. Loud noise from inside engine when oil fill cap is removed. Bosch fuel systems specialist is suspecting timing chain tensioner problem causing timing to be out due to cam chain tensioner?
Assistant: How many miles on the car? How responsive has your car been lately?
Customer: 245000 km. Pulls well, Performance good.
Assistant: Are you fixing your X5 yourself? What have you tried so far?
Customer: I had injectors done by Bosch specialists. I replaced glow plug unit. Fault code indicated glowplug unit was defective. Now less smoke on startup.
Assistant: Anything else you want the mechanic to know before I connect you?
Customer: Car was perfect before it was misfiring due to No5 injector being defective.
Submitted: 1 month ago.
Category: BMW
Expert:  Matt replied 1 month ago.

Hello

yes a stretched or loose timing chain will effect the cam timing and its possible for it to get that bad you will start to get misfires

especially if you have a tinkling / rattling noise

if you were to do a compression test across all cylinders this will show if the timing is out as they should all be within 10-15 psi of each other

and at this millage its not uncommon for a new chain to be required

so if you are planning on keeping the car then I'd say that a new chain and tensioner will be required

parts are about £145 and its a 4 hour job

Customer: replied 1 month ago.
Thanks Matt. I wish to confirm that the car is not misfiring on start-up any more. It does have a fuel smoke which gets less when the car warms up, but you can smell and see the faint smoke all the time. The performance is good. Fuel consumption is 1liter/100km more on the country roads.
I was really alarmed when the Bosch technician removed the fuel filler cap. The faint rattling noise became a loud clatter.
I need to confirm that this clatter noise is probably from the timing chain.
The second matter I do not understand is why the smoke on startup became less over time? Regards. Frederick
Expert:  Matt replied 1 month ago.

Hello Frederick

I think you mean the engine oil filler cap?

a top end rattle can be the timing chain, or sticking hydraulic tappets or even a pulley that's breaking up

but as its louder when you remove the filler cap this points to inside the engine and tappets tend to make a rhythmic 'tapping' noise not a 'clatter' and these engines are prone to timing chain wear its really all pointing to that

as to why smoking gets less over time perhaps you have had a leaking injector that was dribbling fuel - this can make for a smokey start and with miles and a good quality fuel they can sometimes improve?

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