Slight cylinder miss.
 

Hello fellow enthusiasts.

I am having a weird problem with my d24t, where the motor is vibrating/shaking a bit at low rpm. The vibration is present at idle ~700rpm, but worst between 1200 and 1500rpm.
I tried looking for this on google, and found out that V8Volvo had an almost identical problem, some years ago. I tried to personal message V8Volvo, but I'm not sure I did it the right way.

Here's the original message I sent to him, including the link to the forum where he discussed his problem:


I tried typing in google the problem I am having with my D24T. One thing I found was a thread by you, having almost the exact same problem in 2009. However, there was never a conclusion in the thread. The last suggestion was the EGR circuit, but mine doesn't even have an EGR valve. The symptoms are exactly the same as those you were having, only difference being a little shaky at idle too, but much worse around 1300rpm. Above 2000rpm it's probably all gone.
Did you ever figure it out?

Here's the link to your thread I found on some forum through google:

http://forums.tdiclub.com/showthread.php?t=247293

Best Regards Ragnar Eliansson.

Possible 1cyl low on compression maybe?

Some ideas: a bad injector, wrong injection timing, misadjusted valve lash, air getting sucked into fuel delivery, or (as mentioned above) low compression

That one turned out to be a bad pump, either a camplate or head/rotor issue or maybe delivery valve, I was figuring. Never got to find out because that IP self-destructed pretty soon after. Motor was smooth after pump was changed. However, that's not the only possible cause...

Have you checked valve clearances?

Interesting... It could very well be the pump. My original pump was leaking and wouldn't keep the car running on anything but purge. (Lift pump failure). I ordered a reseal kit from Oregon Fuel Injection. However in the meantime, while waiting for that kit to arrive, I came to think about the pump I saved of the old motor I replaced. It had been lying in the trunk of a car on a meadow, summer and winter, possibly empty on fuel for approx. 2,5 years. Sure enough it fired right up, but has been shaky at the mentioned rpms since. I ran the car for too little time with the old pump, to know if the problem was there already. It actually came with a bad pump, as I ordered the whole motor from Denmark, but I was too late to diagnose the pump, for the warranty to cover it... I know it's not the static timing, as some of you mention, as I've tried both .9x and .75 (two different booklet specs) and the problem remains constant.

Valve adjustment is something I've suspected too, along with injectors. Valve clearances are the next thing I will check, although I still haven't removed the valve cover to check if it's hydraulic or shimmed.

Compression "ringwise" however, is not something I suspect, as the motor had a leakdown test done to it, before I bought it and they said it was very good for an engine of its age, and gave me a number of 18. I don't remember what it stood for. I bought the engine almost four years ago, but I probably haven't put more than 1000 kilometres (600 miles) on it. Also it fires right up within the wink of an eye, when cold. Very cold too. And there's NO blowby whatsoever, as long as the oil pressure is up. I have a problem with the oil pressure dropping down to the red field of the gauge at idle speed, when the engine has been running with high to moderate boost for a while after being warmed up. (I know the pressure can be altered by the tension a spring) Anyway. When this occurs I have a tiny amount of blowby. Nothing close to a concern though. It could actually be oil vapor, as the oil is being warmed up so much by the stress. Also what I don't like about the setup, is that the turbo does not have water lines for primary cooling, leaving the oil with the entire job.

Best Regards Ragnar.

Gasoline Volvos seem to go through turbos regularly unless they're watercooled, but the diesel Volvo turbos seem to usually work fine at 300k+ miles. I'm not sure you'd get any benefit from water cooling the turbo, but just have more coolant hoses to leak/replace.