Low compression / rough idle - E53 X5 4.6is
 

Hi there,

I'm quite new here on this forum - thanks much for any tips, comments or advice in advance.

Timing chain and guides have been replaced on our 2002 X5 4.6is less than 100 miles ago. When starting the car in the morning last week, it had a very rough idle, but engine was running sort of fine at higher rpms. We spent significant time searching for the problem and checked all vacuum hoses connections, sensors, ignition components, etc. but couldn't find a problem. We then checked compression and found that bank 2 (driver side) had low compression in all 4 cylinders. We are suspecting a problem with the variable valve timing system (valves off cycle / not closing completely), since it's quite unusual for all four cylinders on just one side of the engine to have low compression from wear & tear.

Did anyone experience a similar problem in the past and can confirm that a problem with the VANOS system might be causing this?

Any other ideas?

Thanks much in advance.

Yeah vanos could definitely be a problem, but it would also throw codes for timing related issues, but since all cylinders on bank 2 show low compression I would assume maybe even a loose chain gear sprocket since there is no pin to guide them gears with the cams there isn't anything that can hold them other but the pressure of the torqued bolt that holds it.


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You can get your hands dirty and check for a loose gear, remove the valve covers, set the crank pulley to TDC and compare cams, if one gear spun a little out of place you'll notice it and you can set the timing back if you get the tools from ebay


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Thanks much for this info.

So, it seems possible that the cam gear bolt did not get tightened enough by the shop who did the timing chain / guides replacement?

Also, do you have to take the whole timing cover off in order to get to the cam gear bolt / or for doing the adjustment? That would be a major pita since it's like 20 hours to get that removed and reinstalled.

But if a shop did the work they should honor their labor. Should be no additional expense to you, just an inconvenience of having the vehicle down for a day or so.

Yes, but I'm wondering if they might just say this is unrelated to the work they did.

If it was less than 100 miles ago... I'd definitely take it back to them.

Good day!

If they did the chain and guides correctly, the loose gear is NOT unrelated... I'd take it back and not indicate you know anything except it is not quite right... Let them figure it out and correct the issue...

"It ran great 110 miles ago before you did the work! Now, it should run better, not worse! Ready GO!"

and see what they say!

Good luck!!

Cheers!!

Yeah, I will definitely take it back to them.

Thanks everyone for the input, comments and advice!

On a lighter note, what is last 7 of vin so I can add you to the registry :thumbup: