Volvo D9 rough idle

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hori

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Volvo D9 rough idle. Changed racor and main fuel filter week ago. Changed racor again today, cleaned housing, diffuser., check valve. Fuel is clean, no water in bowl and fuel clean. All the fuel tanks were cleaned over summer. I have good fuel flow to racor. Everything normal when underway at load no surging and no surging/ rough when at idle in gear. No abnormal smoke from exhaust. Just hunting idle in neutral? and ideas? thanks
 
All regular services including reduction which is less than year old. All is fine when underway just in neutral.
 
Get a Volvo tech to plug a computer in to it. D9 is a complex engine, rough idle could be a great many things. The vod.ia box can determine all sorts of issues really quickly. At idle the D9 engine constantly adjusts the amount of fuel to each cylinder to get a smooth idle. For some reason the ECU is unable to balance the engine out. The Volvo tech will be able to determine injector behaviour and get a sense of any possible compression issues.
A quick and easy thing to try if you have two engines is to swap the cam position sensors over (check/dont loose any shims, check for any dirt or rust on the sensor), if that doesn't help swap the crank position sensors - see what happens. Are there any error codes on the engine display/rev counter LCD?
 
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Interesting thread. Did the issue happen suddenly, or did it worsen over time? Also, how old are your motor mounts (this is obviously something a VODIA computer wouldn't notice)?
 
When it does it take a piece of pipe approx 1 cm dia , suitable length and put one end next to an ear .With the free end use it as a stethoscope and listen to all the cylinders or what have you , valve caps adjacent and so forth .
Basically to determine if all 6 sound the same …..or not as the case will be I suspect .
 
Only thing you can really try without vodia is pull the MAF sensor and check it’s not coked up. It’s the most likely cause of engine surging at idle, that or a split/leaking hose. But generally you hear the air leaks in hoses.
 
Portofino said:
When it does it take a piece of pipe approx 1 cm dia , suitable length and put one end next to an ear .With the free end use it as a stethoscope and listen to all the cylinders or what have you , valve caps adjacent and so forth .
Basically to determine if all 6 sound the same …..or not as the case will be I suspect .
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You cannot get anywhere near the injectors, they are inside the valve cover .
 
vptech said:
Only thing you can really try without vodia is pull the MAF sensor and check it’s not coked up. It’s the most likely cause of engine surging at idle, that or a split/leaking hose. But generally you hear the air leaks in hoses.
Click to expand...
Which hoses are you referring to?
 
hori said:
Volvo D9 rough idle. Changed racor and main fuel filter week ago. Changed racor again today, cleaned housing, diffuser., check valve. Fuel is clean, no water in bowl and fuel clean. All the fuel tanks were cleaned over summer. I have good fuel flow to racor. Everything normal when underway at load no surging and no surging/ rough when at idle in gear. No abnormal smoke from exhaust. Just hunting idle in neutral? and ideas? thanks
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Faulty camshaft sensor .
 
I had somewhat same issue with my 2020-model 440hp D6 engine this summer. It had a rough idle the first 20-30 seconds after starting, if the engine hadn't been used for a while. But if I bleed the air out of the fuel system prior to starting, everything was normal and smooth idle.

With my engine, the cause was the fuel pump, which had to be replaced.
 
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