S40: - Rough idle, diesel 1.9 '96

cmircea · Aug 19th, 2012, 12:41

I have a 96 Volvo S40 1.9 diesel which has a baffling engine issue: at idle, sporadically the engine revs drop to ~500 (from 800) then it suddenly revs to 3-4K, a harsh knock is heard from the engine and white smoke comes out of the exhaust. This happened after a very harsh winter, the car sat unused the whole winter, we had -20C for about a month.

This doesn't occur under load, just at idle, typically at a stop light. Before it starts revving, it dips a bit then wildly rises to 3-4k and a loud bang comes from the engine.

skyship007 · Aug 19th, 2012, 13:10

This sounds a bit like a diesel engine runaway problem, because the over revving and white smoke could be a split turbo seal allowing oil into the intake.
What happens if you turn the ignition off when it over revs?? If it does not stop suddenly then it is definiteley is a blown oil seal and I would recommend not driving the car, because you are at risk of a full runaway.
If the car does suffer a runway just jam into into 4th asap to stop it.
If the oil seal is bad then the turbo bearings are probably badly worn, so you will need to replace the turbo.

Aug 19th, 2012, 12:41	#1
cmircea New Member Last Online: Oct 5th, 2012 16:55 Join Date: Aug 2012 Location: Craiova	Rough idle, diesel 1.9 '96 I have a 96 Volvo S40 1.9 diesel which has a baffling engine issue: at idle, sporadically the engine revs drop to ~500 (from 800) then it suddenly revs to 3-4K, a harsh knock is heard from the engine and white smoke comes out of the exhaust. This happened after a very harsh winter, the car sat unused the whole winter, we had -20C for about a month. This doesn't occur under load, just at idle, typically at a stop light. Before it starts revving, it dips a bit then wildly rises to 3-4k and a loud bang comes from the engine.

Aug 19th, 2012, 13:10	#2
skyship007 Premier Member Last Online: May 2nd, 2018 08:14 Join Date: Sep 2011 Location: DownSouth	This sounds a bit like a diesel engine runaway problem, because the over revving and white smoke could be a split turbo seal allowing oil into the intake. What happens if you turn the ignition off when it over revs?? If it does not stop suddenly then it is definiteley is a blown oil seal and I would recommend not driving the car, because you are at risk of a full runaway. If the car does suffer a runway just jam into into 4th asap to stop it. If the oil seal is bad then the turbo bearings are probably badly worn, so you will need to replace the turbo.

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