Rough idle in 740 1990 Volvo Smooths out a bit when driving

Could be anything. Vacuum, valves, rings, tune up. Check vacuum lines. Then check compression before you do a tune up. If you have bad compression in a cylinder, tuneups don't help. In that case, either drive it till it dies or replace/rebuild the engine.

you have a bed coil (s). That's what causes misfire. Your DIC should be specific about which cylinder coil you're having trouble with.

you have a possible vacuum leak somewhere or maybe clogged egr

1997 escort idles rough, the first thing is to make sure the throtlebody plate is clean. This sounds like the idle may be staying to low at times if it smooths out with ac on, when the ac is turnned on the computer raises the idle a touch to make up for the strain on the engine from the ac compressor, clean throtlebody and look at and clean idle air control valve, if this valve is not controlling the idle when needed the engine will idle lower than normal and cause a rough idle.
Another thing is the sparkplug wires, take a look at those, if at night or with a good eye use a spray bottle and spray a mist over the wires and watch for any sparking, this spark may be very small so look at each wire closely or may be big enough to see and hear. this is where i would start. good day.

First u have to take it to ur car dealership they have scan tool the scan tool will read the fault code and tell u which part or sensor is in faulty that way it's easy fix

You didnt adjust the valeves properly


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change plug and wire if its been a while most cars have 90000 miles platinum plugs in them.but the wires wear before plugs.so change plugs and wires.+clean fuel injectors .change fuel filter and air filter.if car still run rough your idling to low.have idling check .

Try a popular fuel stabilizer like Seafoam sold just about anywhere.

a rough idle/high idle is indicative of a malfunctioning TPS(throttle position sensor) this is located on the throttle body ,is attached with (2) screws/bolts to the throttle body housing right off the butterfly shaft. it has either 2 wire or 4 wire plug. the replacement part can be purchased at locale auto parts store. I would also agree that a full service and tuneup be done. this will help with performance and will increase the fuel efficiency. please rate this...thanks

It could be the filter. Has the fuel been changed after storage? I would also thing the Carburetor or the fuel injectors might need to be cleaned.