Volvo V8 misfire help

[KarelH]

Hello, please provide information. I have a problem with Misfire on a Volvo V8, picture from Vida. I changed the spark plugs and coils and nothing, still the same. I also checked the grounding and nothing. I know it has been addressed here, but no new results. Thank you very much.

[Vova585]

So not actual injectors(8 of them on 2 banks would be hard to imagine). Spark plugs and coils are out of equation as well(replaced and nothing).
Things to possibly try- check the fuel pressure(not sure if Yamaha v8 has separate port vs electronic monitoring).
Check and clean MAF.
Find in vida parameters for MAP sensor and coolant temp and check if they are reasonable.
If able- perform the smoke test on the system, maybe you have large vaccuum leak somewhere(cigarette tester would be the cheapest option vs baby oil tester, haven't used either option, but read about them and people report good results for them.
You can disconnect upstream sensor on one of the banks and see if default strategy will still result in misfire in those cylinders.
Have you checked your timming marks? It is a chain, but maybe it is overstretched and causing ignition timming issues.
Any problems with mechanical components that can possibly "trigger" knocking sensors to see misfire?
What are the long fuel trims on this car?
Have you checked PCV system on this car?
Best would be to perform cylinder balance test with in cylinder transducer so you will know is it ignition, timing, or compression. Try to find a good diagnostician with professional scope and knowledge to read wave forms.

[KarelH]

I have one more option, is it possible that the auxiliary timing chain is somehow jumping? The previous mechanic said that the chain tensioner was not working, so could that be it? Thank you, on the live data in Vida I saw that there was a problem on the head where the tensioner was bad. It also tells me that the exhaust cam has high values. Thank you

[Vova585]

Thats some serious sludge in that engine..I would question in what condition are the VVT hubs and solenoid with all that gunk. Try to use avoid using engine cleaners at this time and rather use regular oil with frequent oil changes(will be safer than dumping all that junk throughout the engine). I am not sure about design of tensioner on v8 engine, but if it is hydrolic based on oil pressure, i can see how it would stop working.
Sure check the timing first, but now misfire are only on 3 cylinders based on your vida photo

[KarelH]

Thats some serious sludge in that engine..I would question in what condition are the VVT hubs and solenoid with all that gunk. Try to use avoid using engine cleaners at this time and rather use regular oil with frequent oil changes(will be safer than dumping all that junk throughout the engine). I am not sure about design of tensioner on v8 engine, but if it is hydrolic based on oil pressure, i can see how it would stop working.
Sure check the timing first, but now misfire are only on 3 cylinders based on your vida photo

thank you very much, I also found out that the car is not cooling at all, the upper hose is very hot and the lower one is cold. I replaced the thermostat but it didn't help. any tips? thanks

Is there any way to adjust the auxiliary chain timing without having to remove everything?

[Vova585]

I am not an expert on V8 Yamaha, since never had to work on one. It would be best to look up water cooling diagram for this car. Some engines are notorious for having hard time to get "air out" and require vaccuum coolant exchange procedure in order to evacuate all the air(most of newer 4cyl turbo engines). Recently also was studying the case of overheating vw 1.4 diesel and the coloring was restricted coolant flow through the heater core(mind blowing). If possible try to isolate that contour by bypassing. Given all the issues with the misfire and cooling, have you done the exhaust leak test on the coolant? Maybe the problem is mechanical from prior overheating? Are you the original owner, or do you know when the last time this car was "ok"?

[KarelH]

I am not an expert on V8 Yamaha, since never had to work on one. It would be best to look up water cooling diagram for this car. Some engines are notorious for having hard time to get "air out" and require vaccuum coolant exchange procedure in order to evacuate all the air(most of newer 4cyl turbo engines). Recently also was studying the case of overheating vw 1.4 diesel and the coloring was restricted coolant flow through the heater core(mind blowing). If possible try to isolate that contour by bypassing. Given all the issues with the misfire and cooling, have you done the exhaust leak test on the coolant? Maybe the problem is mechanical from prior overheating? Are you the original owner, or do you know when the last time this car was "ok"?

Hi, I think I found the problem, the auxiliary timing belt tensioner still doesn't work, my theory is that at low speeds it moves the cam, but when I go to higher speeds everything is fine, there is no sign that the engine is running irregularly like at idle. The question is, is there a way to replace the tensioner so I don't have to remove the main timing belt? Thank you very much

[BlackBart]

Could be. If that chain tensioner isn't correct, then it could be your valve timing is off at certain rpms and it's not firing correctly. My old Audi A4 4-cyl had that type of chain tensioner and timing advance. The replacement process was to carefully mark the links and teeth with white paint marks, pull all the cam bearing caps so you could rotate the camshaft up enough to unbolt and remove the tensioner and replace.

I don't think there should be that kind of slack in the chain.

[scot850]

Sorry I did not see this earlier. The V8 is known for timing chain tensioner and guide issues. Part of the reason I never bought one, along with the valve cover gasket leaks and the difficulty getting starter motors when the oil leaks into the starter and takes it out too.

I wish you luck!

Neil.