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Hunting idle at cold start

Help, Advice, Owners' Discussion and DIY Tutorials on all Volvo's "mid era" rear wheel drive Volvos.

1975 - 1993 240
1983 - 1992 740
1982 - 1991 760
1986 - 1991 780
1990 - 1998 940
1990 - 1998 960
1997 - 1998 V90/S90

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Smar1991
Posts: 6
Joined: Mon Dec 03, 2018 5:02 pm
Year and Model: 1993 940
Location: VA
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Hunting idle at cold start

Post by Smar1991 »

My 93 940 nonturbo has a hunting idle at a cold start. If I let it run for about 10 min it settles down, but initially it revs constantly from .5-1 rpm. Additionally, I've noticed that I have a pretty sluggish acceleration (more than the normal sluggishness of these nonturbos). I put in new plugs, wires, vacuum lines, and distributor cap and nothing's changed. I know the b230 isn't known for having the smoothest idle, but I'm worried the ecu might be going bad since it has 242,0000 miles on it. Any ideas?
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RickHaleParker
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Re: Hunting idle at cold start

Post by RickHaleParker »

Idle air control valve (IAC). You might try cleaning out the IAC with MAF sensor cleaner or Carb cleaner.

It could also be leaks in the intake manifold gasket that seals up when the engine warms up. You can locate intake manifold leaks with starting fluid. Spray the starting fluid around the intake manifold gasket when the engine is idle hunting. A leak will suck in the starting fluid and you will hear the engine surge.


Idle air control valve (IAC).
IAC.gif
IAC.gif (11.83 KiB) Viewed 220 times
1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package.
2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000.
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