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Re-Post...Help! (George, Are you there?)[740-760/1990] posted by Chris Mullet on
Friday, 19 June 1998, at 11:36 a.m.
I've got a 1990 740, non-turbo, gas, auto trans with about 82,000 miles. I'm running 87 octane. When in gear, it seems to idle a little rough. It's
not a roughness like a rythmatic miss, but feels more like it's running on the lean side or just idling a bit slow (or fast). It sets up a sort of
rezination that can cause door panels to rattle, etc. When in neutral it purrs like a kitten. Throttle response is excellent. If the idle speed is not
right, then I would tend to think it's a little fast (about 650-750 RPM on the car's tach), as it tugs fairly strong when dropping it into gear.
Compared to my mother-in-law's 1989 740, my idle speed doesn't seem to correct with as much gain when putting in gear or turning on A/C.
Power-wise, the car goes down the road great. Given this background:
What is the proper idle speed in gear?
What is the proper idle speed in neutral?
Could octane be too low?
How does one verify/correct idle control system?
Could auto trans be trying to engage at too low of engine speed?
Could worn engine mounts cause this?
Any ideas are appreciated.
Thank You Very Much,
Chris
Re: Re-Post...Help! (George, Are you there?)[740-760/1990] posted by Ed Preston on
Friday, 19 June 1998, at 1:05 p.m.
How's the gas mileage? When was the last time you replaced the oxygen sensor?
--Ed
Re: Re-Post...Help! (George, Are you there?)[740-760/1990] posted by Chris Mullet on
Friday, 19 June 1998, at 1:26 p.m.
Mileage is still real good as far as I know. I haven't done the math lately. Can I swap the O2 sensor with the 1989 740 as a check? The one with the problem is 1990. Both are non-turbo.
--Chris
Re: Re-Post...Help! (George, Are you there?)[740-760/1990] posted by Steve Ringlee on
Friday, 19 June 1998, at 3:52 p.m.
It wouldn't be an exhaust resonation, would it? Volvo has a TSB for an extra intermediate pipe bracket to eliminate exhaust pipe vibrations, which can sound suspiciously like idle problems. I put it on and the vibrations when idling in gear stopped. Goes between the transmission and the IP.