[Markm87]

I purchased my 2018 XC90 T8 around 6 months ago now, and have had problems the engine since day one, specifically knocking noise under load and misfiring on all cylinders. It was purchased from Volvo, with low mileage (35,000) and full service history.

It has been back to Volvo for diagnostics/repair many times since (at least 7 times), staying there for over 2 weeks on many occasions. Although they have confirmed there is definitely an issue, and can log misfires on all cylinders, they have failed to find a solution. Apparently the lack of fault code makes it almost impossible for them to find the fault!?

There seems to be no hope of Volvo's experts finding a solution any time soon and so I am hoping that users here may be able to offer knowledge, advice or share experience of similar problems.

I have an OBDII diagnostic tool and so can read/monitor parameters to help diagnose if anyone has any suggestions. I have used this so far to confirm the misfires.

As an example, a 20-30 minute journey will often have misfires logged on all cylinders, some more than others, up to around 10 misfires on each cylinder.

There seems to be two ways in which the problem presents itself, other than the logged misfires, I will provide more detail below:

Cold Start Noise/Shake
The video below shows the engine started from cold.

The engine RPM was raised to just under 2,000 RPM in this video where the problem is most noticeable.

This is very repeatable, it will occur anytime the engine is started from cold (an hour or two after being parked is usually enough), it can be noticed at idle without raising the RPM but is more subtle, raising to just under 2,000 RPM and it becomes very noticeable.

I have noticed on a cold start, the engine will fast idle for around 30 seconds, remaining at around 1,400 RPM before settling down to normal idle at just under 1,000 RPM. It is during this ~30 second fast idle period when the above problem occurs, after this period, the noise/shake will go away and raising the RPM will no longer cause the problem.

Knocking Noise Under Load
This audio clip below was recorded when driving on a slight incline at around 20MPH:

The noise will be apparent when driving at lower speeds (<30MPH) on the petrol engine, for example when the hybrid battery is depleted or set to charge, or even in AWD/Polestar Mode. The noise will be more apparent under load, often louder when going up a hill.

Again this noise is very repeatable, a low speed drive around town or around a car park it will most likely be heard, although the volume of this noise does seem to vary.

I have noticed that during the first 30ish seconds of the petrol engine starting, this noise will not be present, with the engine running smooth and quiet while driving. This is noticeable when starting to drive during the fast idle period mentioned above, or when driving along in Pure mode as the battery dies forcing the engine to start, in both cases the engine seems to run smooth and quiet for around 30 seconds before the knocking noise begins.

There seems to be a crossover point between the two problems above, where one stops and the other starts, this seems to be around 30 seconds after a cold start. I am guessing this is when the engine switches between open/closed loop mode.

If anyone has any suggestions, advice or experience with similar problems your input would be greatly appreciated.

 

[BenjaminD]

I'm amazed it's still running. It sounds awful. Why won't Volvo replace the engine?

 

[VolvoFaRmeR]

Sounds like your dealership service department sucks. Time to ask for a regional Volvo Corporate tech to be flown in. If it can't be fixed you are entitled to a buy-out or buy-back, plain and simple.

 

[EngTech]

Should Have Been Torn Down Immediately !

or

LAWYER !

 

[anarekist]

That much misfiring.. that engines toast

 

[Dyno]

Vacuum leak? Look for codes and condition relating to "lean" or "fuel trim". Capture freeze frames when the codes are created.

 

[Pioneer4x4]

Sounds like your dealership service department sucks. Time to ask for a regional Volvo Corporate tech to be flown in. If it can't be fixed you are entitled to a buy-out or buy-back, plain and simple.

On a car bought 4 years old, nah.

 

[zak]

Have heard of injectors going bad

 

[VolvoFaRmeR]

On a car bought 4 years old, nah.

If it’s been an ongoing problem for years…why not? It’s it’s under warranty and has been atrmoted multiple times over and over….then it likely could be lemon lawed. The first step is volvo Corporate tech. That’s their job. Why would they not? I guess I’m unsure if the cars in servicr date and owner history (which makes a difference obviously). But for a dealer to be shown a video and repeatedly have the problem replicated and not be able to fix it? Sounds like a pretty sick dealership to me.

 

[Dyno]

Yeah, big problems are generally the easiest to find.

Something global that affects all cylinders, not just one.

• Vacuum leak
• Fuel Pressure
• ECU
• Fuel Quality

I'd want to see a Freeze Frame. It is throwing codes.

 

[SwedishDoomGoblin]

I wonder if they've checked the integrity of ALL related wiring, battery cables, grounds, etc. Sometimes electrical issues can cause all sorts of wacky things that are tough to locate and often misdiagnosed as some sort of a parts failure. Not saying that's what it is, but hopefully they've tried ruling everything out they can.

 

[BolboLubber]

I wonder if they've checked the integrity of ALL related wiring, battery cables, grounds, etc.

These are my thoughts as well.
I'd suggest Volvo replace the main wiring harness, or at least do testing on the harnesses that lead to the engine/fuel system/ignition system.
I'd be willing to bet that it's where the problem is (assuming the vehicle is running on high octane fuel etc.).

 

[Pioneer4x4]

If it’s been an ongoing problem for years…why not? It’s it’s under warranty and has been atrmoted multiple times over and over….then it likely could be lemon lawed. The first step is volvo Corporate tech. That’s their job. Why would they not? I guess I’m unsure if the cars in servicr date and owner history (which makes a difference obviously). But for a dealer to be shown a video and repeatedly have the problem replicated and not be able to fix it? Sounds like a pretty sick dealership to me.

UK laws are different, but within 6 months, maybe. I think they updated protection on used cars like some states here do.

 

[orcking]

What buggles my mind about these giant car companies. How do they not have a knowledge base of videos and advices from different problems of their cars from around the world.... With video and probably solution or flow charts especially if it goes to techs at headquarters. I'm pretty sure that is not the first time this problem arises. And the incompetent techs at the dealers are unreal....
My brother in law just took his ram truck to dealer for 4wd service light under warranty.. Charged him $900 . Two days later the light came back.. went there they wanted to charge him some more....

The vip warranty for example should require video evidence and steps took to diagnose..

 

[volvogod]

Can you list all of the codes that you have seen and that the Volvo dealership has recorded? Since you purchased the car used 6 months ago any ideal about past repair history? I am not sure about your market, here in the US, Volvo is very helpful about diagnosing problems like this. Any idea if the dealership has inspected the spark plus for being worn out, loose or have installed a new set? The injectors could be an issue or high pressure fuel pump?. If the engine has had internal repairs, it is possible that the balance shaft backlash was not adjusted properly. Below is a pic of the balance shaft assembly. The balance shaft assembly will cause engine shake, not sure about the misfire codes.
You may have more that 1 problem. Hopefully the dealer and Volvo will get this corrected.
---------------------
The task of the balancer shafts is to smooth out the engine's oscillations and they are driven by a gear on the crankshaft. The two counter-rotating balancer shafts are located in their own housing in the oil sump. Drive to the balancer shafts is via the crankshaft to one balance shaft, which in turn drives the second balance shaft. One of the balancer shafts' gears is two-piece. The "narrow" half (Scissor gear) is spring tensioned in the opposite direction to the "wide" half. It provides silent backlash elimination. This technology is already found in the gear on engine B63x4x. To ensure correct backlash, the balance shaft housing is shimmed to the engine block at the assembly plant.

 

[VolvoUhu]

If it’s been an ongoing problem for years…why not? It’s it’s under warranty and has been atrmoted multiple times over and over….then it likely could be lemon lawed. The first step is volvo Corporate tech. That’s their job. Why would they not? I guess I’m unsure if the cars in servicr date and owner history (which makes a difference obviously). But for a dealer to be shown a video and repeatedly have the problem replicated and not be able to fix it? Sounds like a pretty sick dealership to me.

Not necessarily under warranty and how they treat a systemic/recurring issue like this is also different than may be expected in NA market. UK and EU warranties are not the same as NA warranties (length of time and mileage).

 

[Markm87]

Vacuum leak? Look for codes and condition relating to "lean" or "fuel trim". Capture freeze frames when the codes are created.

There are no codes logged when I checked using a basic OBDII tool, also Volvo have said there have been no codes logged on any of the many occasions they have had the car back. I do find this odd though, no fault codes ever logged, even with the number of misfires shown regularly on the counters. The counters reset to 0 when the engine is turned off, I do wonder what the thresholds must be before throwing an actual fault code though?

As for the possible lean condition, a quick check of the long term fuel trim shows +4.6%. I will monitor this along with the short term fuel trim over the next few days and report back.

 

[Markm87]

If it’s been an ongoing problem for years…why not? It’s it’s under warranty and has been atrmoted multiple times over and over….then it likely could be lemon lawed. The first step is volvo Corporate tech. That’s their job. Why would they not? I guess I’m unsure if the cars in servicr date and owner history (which makes a difference obviously). But for a dealer to be shown a video and repeatedly have the problem replicated and not be able to fix it? Sounds like a pretty sick dealership to me.

I still have 6 months remaining on the 12 month extended warranty, all work done so far during the many visits to the dealership has thankfully been covered by this, especially seeing as all work completed so far has been worthless.

I am still in contact with the Volvo dealership who sold me the car, and they still insist they will get the problem solved and it won't be at a cost to myself, however I am now half way through the warranty and I have lost all hope that Volvo are capable of fixing the problem. They have been in discussion with the national Volvo Master Techs who suggested possible water ingress, the dealership removed and inspected the ECU, lifted carpets, checked filters etc. and found no reason to suspect water ingress so that seemed to go nowhere.

 

[Markm87]

Yeah, big problems are generally the easiest to find.

Something global that affects all cylinders, not just one.

• Vacuum leak
• Fuel Pressure
• ECU
• Fuel Quality

I'd want to see a Freeze Frame. It is throwing codes.

I can try get some fuel pressure plots using the OBDII, do you have any suggestions of what other sensors i should monitor?

I think we can rule out fuel quality, the problem has been consistent throughout the 6 months of ownership so far and I have purchased premium fuel from various reputable stations.

 

[Markm87]

I wonder if they've checked the integrity of ALL related wiring, battery cables, grounds, etc. Sometimes electrical issues can cause all sorts of wacky things that are tough to locate and often misdiagnosed as some sort of a parts failure. Not saying that's what it is, but hopefully they've tried ruling everything out they can.

I don't believe they have looked into any of the wiring, a valid point though.