I originally posted this question:
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posted by rjritterjr on Sat Dec 8 07:27 CST 2007
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last visit: Sat Dec 15 12:03 CST 2007
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My 94 940 N/A, 199,850 miles has been intermittently missing at highway speeds for awhile now. It feels like it misses an entire revolution while running at 70-73 mph, steady speed (not accelerating); sometimes also at 45-55, also steady speed, not accelerating. It doesn't happen often, may once or twice on a 30 mile trip. All I do is drive back and forth to work, 30 miles each way, about 20 miles of that on interstate. I recently replaced the distributor, plugs and wires; gas filter; cleaned the IAC valve; new air filter; alternator. None of these things have solved the problem. Gas mileage remains steady at just over 24.3mpg consistently. It does not normally miss under load/acceleration. It has not stalled on me. I'm not using the cruise either.

One thing I know is bad is the EGR temp sensor -- according to the self-diagnostic. The check engine light has been on for awhile due to this problem. I can't imagine this would be the cause, but maybe it is.

Does anyone have any ideas?
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I replaced the distributor cap; no change. I bought an aftermarket power stage (Huco or something) that made things worse; exchanged it for a Bosch, but did not get a chance to install it. Turns out the harmonic balancer came loose while driving a few days later. Replaced it and the crank timing gear that got messed up in the process. Haven't had any missing problems of any kind since then. Still have the Bosch power stage new in box. Also replaced the EGR temp sensor, but it did not have any effect that I recall, other than to eliminate the check engine light.

Thanks for all of your input!

1994 Volvo 940 NA 204k miles