Revs up and down constantly from 1000 to 1600rpm

Derry · Feb 20th, 2020, 14:44

Volvo 850 1996 10v Auto

When warm, in N car revs up and down constantly from 1000 to 1600rpm, but when you put it in any of the gears it idles fine at 900.

I have cleaned throttle housing and idle control valve (internal plate rotates smoothly) and replaced the hose and elbow going to inlet manifold, as far I can see other vacuum elbows and hoses are ok. Other than this car drives fine.

I don’t get any codes just 1-1-1, and no warning lights. I did have an horrible issue for couple of weeks when car would just die totally while driving but would starting again after 10min and drive absolutely fine. New fuel pump relay seems to have solved that issue. I do know that the PCV needs serviced badly as it has never been done + the timing belt.

NI_Volvo_Nut · Feb 21st, 2020, 12:42

You have an inlet air leak

Baffler · Feb 21st, 2020, 16:01

And, if not an air leak, possibly the Engine Coolant Temperature sensor sending incorrect info to the ECU.

Feb 20th, 2020, 14:44	#1
Derry Member Last Online: Apr 17th, 2024 22:10 Join Date: Nov 2006 Location: NI	Revs up and down constantly from 1000 to 1600rpm Volvo 850 1996 10v Auto When warm, in N car revs up and down constantly from 1000 to 1600rpm, but when you put it in any of the gears it idles fine at 900. I have cleaned throttle housing and idle control valve (internal plate rotates smoothly) and replaced the hose and elbow going to inlet manifold, as far I can see other vacuum elbows and hoses are ok. Other than this car drives fine. I don’t get any codes just 1-1-1, and no warning lights. I did have an horrible issue for couple of weeks when car would just die totally while driving but would starting again after 10min and drive absolutely fine. New fuel pump relay seems to have solved that issue. I do know that the PCV needs serviced badly as it has never been done + the timing belt.

Feb 21st, 2020, 12:42	#2
NI_Volvo_Nut Volvologist Last Online: Dec 6th, 2023 11:13 Join Date: Aug 2008 Location: Bangor - Norn Iron View Photos By: NI_Volvo_Nut	You have an inlet air leak __________________ What's the matter with the car I'm driving? Can't you tell that it's out of style? Should I get a set of white wall tires? Are you gonna cruise the miracle mile?

Feb 21st, 2020, 16:01	#3
Baffler Premier Member Last Online: Yesterday 19:44 Join Date: Dec 2002 Location: Co. Limerick, Ireland	And, if not an air leak, possibly the Engine Coolant Temperature sensor sending incorrect info to the ECU. __________________ Liam... '96 854 TDI SE, '99 V70 2.5D S, '05 C70 2.0T Collection, '05 S80 2.0T SE, '15 V70 D4 SE Lux Nav.

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