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Hi guys
I usually write about my wife's 850, but this time it is about my old, reliable non turbo 740. The problems began a couple days ago. Since that time, the symptoms have increased in severity but not in type (no new symptoms, just the same ones are noticably worse and more frequent). The power is still good.
The symptoms are starting and idling fine cold even around 15F. After idling to warm up for 5 or 10 minutes, the idle would drop to seemingly about to quit and then the engine would surge to a little above normal rpm and then settle down again (it did this once in a great while for years but with no other symptoms). Sometimes the revs cycle from plus to minus a couple hundred rpm's over a few seconds time over and over. Pushing the gas to raise the idle to a little over a 1000 rpm seems to smooth things out. During cruise only, it stumbled (lost power) slightly (the tach showed a few hundred rpm's drop) for a few seconds several times in a row. It still has good power with no stumbling even under high power demand (foot to the floor from 45 to 65 mph). If the engine is still warm, it fires but won't start without pushing the gas pedal a bit (usually a no-no), but it does start without too much trouble. The air temperature has warmed up to above freezing and I'm good about using Iso dry gas with each tank, so a frozen fuel line seems unlikely. I cleaned the throttle body (pretty clean for 318K miles), but it made no difference.
Another thing the car would do once in a great while in the past (possibly unrelated) is seem to quit for just a moment when pulling away after idling at an intersection, but then catch and drive away fine. It kind of felt like I'd hit the gas exactly as it was down shifting from second to first as I was coming to a stop except I was already stopped.
I've searched the other postings and FAQ's and can't find anything that covered all of these unusual symptoms (starts and idles good cold, but once warm, poor idle, stumbles at cruise, yet good power). The FAQ's have in the past been right on and an absolute God send.
Thanks in advance
Dave
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'97 110K+miles 850 grey wagon, '91 300K+ dark grey 740 wagon (130K driven since purchased & has thankfully quit only once), '89 200K+ grey 740 sedan (gave as gift to daughter)
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