Hi,

2006 Volvo XC90 2.5T. So the other day we were cruising with the family from a trip to Melbourne (160km away from home) and about 20km from home, engine light starts flashing and engine starts running rough. This was just after going over a hill so the car was in high revs as cruise control had kicked down. Since it was quite late, I nursed it home. Next day, I remove plugs and notice plug no. 1 looks like it's not "burning". So change all plugs and same issue. If you disconnect coil on number 1 during idling, there is no change. If you disconnect any other coils, Engine runs rougher. Ordered new coil from FCP. Coil has arrived and installed. The engine is still running rough and no spark in cylinder 1. It's not the coil as the coil works fine in another cylinder. I'll try and get the codes pulled out but at this stage I'm quite confused as to why one cylinder would not fire. ECU? Timing off by a few teeth?

Thanks

Steve

It could possibly be bad ignition coil wiring.

Think simple

    ramrod

    It could possibly be bad ignition coil wiring.

    Think simple

    Spark plug work in another cylinder? Could be that simple

      Thanks guys - I wish it was that simple. Just did a compression test and Cylinder 1 has no compression :(. I'm now even more confused. Car has been running fine - serviced on time every 10k, use 98 octane, synthetic oil and timing belt kit including water pump was done just 10km ago. It developed a RMS leak a few months ago and was booked in on the 24th for this change. Now I have to deal with the possibility of a broken valve :(. What could cause this? Car has been going fine. Its done 272k though and I bought it at 160k a little over 5 years ago. Its been fairly well maintained though thats why I'm a bit confused.

      Cheers!

      Steve

      borescope would provide quick answer but my first thought is burnt valve

      https://www.youtube.com/watch?v=cmj1SP8rcrQ

      Early PCV valves in the inlet manifold can lose the retaining pin which will be sucked into the inlet on cylinder 1...

      7 days later

      Hi guys. So I managed to take a photo from inside the cylinder facing upwards using a very flexible USB horoscope. Exhaust valve is clearly gone. I'm hoping it's not the PCV retaining pin that has caused this because that just sounds scary. Any how, we'll know what else is damaged on Monday when they take the head out.

      Thanks.

      Steve

      Wow Steve. Nice photo. Really sorry. You didn't get to see the bore or the piston ? The problem is how long the cause was bouncing around before punching the valve. How much damage to the bore and the piston ? The valve is a relatively easy replace.

      A few weeks ago I did the complete PCV system on a T5 XC90 and replaced the check valve. 170,000km. Slightly disappointed to see that it looked as good as new despite being the old design - but the new replacement is a much better part. I've been at the owner to do the job before it caused issues, ever since watching that video. Was starting to think that it might not be that common an issue after all. Still hope it wasn't in your case - although the interesting question is whether the ball and retainer are still in your banjo fitting... ?

      Small consolation for you, but at least you'd have an explanation for what happened - valves tend not to disintegrate spontaneously...

      21 days later

      The Cylinder head is out. So it turns out that it was not the retaining pin of the PCV. The exhaust valve seems to have just disintegrated. Cylinder wall was all nice and smooth and piston is good. No sign of the piece that broke off. What I noticed is that there was a lot of carbon built up on the valves. I have only ever used 98 octane. The spark plugs were overdue for replacement though - could this cause high carbon build-up?

      Now finding the head gasket for this has been tricky though. I've attached the VIDA photo for the Cylinder head. They come in 2 flavours. My engine number is for the later model however a quick check from the interwebs and these gaskets look exactly the same. Maybe the material is different? If the material is the only difference, will it be ok to use either?? Would appreciate any input from someone who know about this.

      Cheers!

      Steve

      Volvopartswebstore lists 30637366 as being superceded by 30637066, and FCP lists 30637066 as a MLS type and suitable for your car. It doesn't look as though the earlier one is commonly available any more which would seem to indicate that it's been replaced.

      Carbon buildup is also caused by oil burning - as well as type (and regularity oil changes...) it's possible that oil is leaking into the turbo or that your PCV may be letting oil mist through...from what I've seen there is usually a lot of oil in the inlet pipework for turbo engines, and it's of course getting sucked through the engine eventually.

      I wouldn't be worried about the amount of carbon if it's like the burned out valve, that's fairly common unless the engine sucks water in (head gasket failure etc) in which case extreme steam cleaning removes the carbon.

      a month later

      Hi guys,

      Just an update and a question. Head has been rebuilt, PCV done all seals including RMS done, water pump, and timing belt kit. I believe the copper washers for the Turbo pipes have been done. The question - the cylinder head was taken elsewhere to be re-built and the VVT pulley's were loose..so they must have removed them during the rebuilt. However, they look like they only go one way? We've assembled head, timed engine. Turned engine on the ground many many times by hand - goes smoothly and marks align all the time. However we are getting weird readings for compression when we try and start car. Do the lifters need to fill up with oil before they start working properly for this engine thus the weird compression readings? We are sure timing is correct but we are also not cranking it for long. Has anyone done this kind of cylinder head job and should we just crank it for longer to see if the oil pressure needs to build up on the lifters?

      Cheers!

      Steve

      pretty expensive way to test by starting it if you think its not right.........

      You need the cam locking tools to have any chance to set the vvt pulleys correctly.

      The pulleys can be fitted 360degrees as there's no keyway, plus there's a process for ensuring correct tension between the gears.

      Once the centre bolt is tight there's also free-play in the gears so the chances of the cam pulleys being anywhere near the correct location are incredibly slim.

      Don't crank it anymore, hopefully you haven't damaged the new valves.

        timbo

        You need the cam locking tools to have any chance to set the vvt pulleys correctly.

        The pulleys can be fitted 360degrees as there's no keyway, plus there's a process for ensuring correct tension between the gears.

        Once the centre bolt is tight there's also free-play in the gears so the chances of the cam pulleys being anywhere near the correct location are incredibly slim.

        Don't crank it anymore, hopefully you haven't damaged the new valves.

        Ohh deer....

          We used the Cam locking tool. @timbo you mentioned a procedure for ensuring correct tension between the gears. Do you know where we can get more info on this? As I said, timing marks are spot on. When we turned the engine when on ground the first time, we did it very carefully and it went round good many many times with no issues timing marks spot on. Kinda confident valves are ok? Compression test is where I'm confused - we would test and get only 50. Test again and get 100. Test again get 80. Then get 50 again. This is happening across on all cylinders. Also noticed that the crank is very sluggish..even with no spark plugs on, its very sluggish. Battery is new. Code reader is reading ECM 340B inlet camshaft sensor -signal missing.

          Cheers!

          Did you fit the intake/exhaust camshaft tonewheels at the rear of camshaft correctly? Also check the camshaft sensor wasn't damaged on installation (have seen them get caught against tonewheels and snap on install)

          I'm fairly sure your engine will have solid lifters, there's also a special tool/process for setting valve clearance if valves are replaced. If machine shop is switched on/old school it's doable without the tools but time consuming.

          I can give you a full rundown tomorrow but Volvo setup process is as follows. Not trying to be patronising but just trying to explain clearly, as can be hard to visualise text explanation.

          **Timing marks are essentially irrelevant, unless you've set everything up correctly**

          ***Gears have free play (move left to right) when centre bolt is tight - when fitting belt/aligning timing marks gear should be held clockwise against limit stop.***

          ***The centre bolt is the torx bit behind the sealing plugs visible in the centre of the gears of your picture***

          Camshafts locked

          -loosen the 3x 8mm bolts holding gear to vvti hub, turn the gear completely clockwise and tighten 3x 8mm bolts

          - fit vvti gear/phaser and tighten centre bolt slightly (just enough to grab) *doesn't matter where timing marks are at this point*

          -turn vvti gear clockwise against limit stop via the outer 8mm bolts, loosen the centre bolt and wind the vvti gear clockwise until timing marks are 1 tooth past alignment.

          -tighten centre bolt (I think it's like 120nm)

          -Fit blanking plugs

          -loosen the 3x8mm outer bolts, and align timing marks

          -Fit the timing belt and set tension

          -hold the vvti hubs clockwise against limit stop via the centre torx bit plug, while tightening the 3 outer 8mm bolts on each gear

          It's not just about locking the cams... the VVT units have an internal stopper and must be rotated clockwise against the internal stopper when the timing marks are aligned. When they are released to be free, they can rotate back 2 teeth so it's possible both cams are out of phase with the crankshaft. Is the inlet cam sensor plugged in? The fault code can be due to the intake cam being out more than 10° from where it's meant to be.

          Also, the lifters are shimmed and not hydraulic so it's not oil pressure.

          Thanks so much guys @timbo and @VolvoMike for your responses. @timbo nothing patronizing at all mate :). This car has has 3 timing belt kit changes by the same mechanic (this being the 3rd) and we've never had an issue with the timing. Granted the other 2 times the head had not being removed but I would like to say the procedure would be the same even if the cam shafts were off?

          Will check cam shaft sensors and tonewheels tomorrow. If the valves were bent, would we have any compression at all?

          Thanks for the procedure @timbo. You should document (if you havent) it and make it a sticky. Could save someone (me included) some grief :)

          Cheers!

          Yeah changing the timing belt is straightforward enough that you don't need the locking tools, i can do them in half an hour the dramas start when you remove the gears from the camshafts

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