92 Chevy C1500 Running Rough

Hello.

Have a '92 Chevy Silverado with a 350 engine and auto tranny. It has 278,000 miles. (engine not original has around 70,000 miles-transmission rebuilt 40,000 miles ago) Getting a problem now of rough idle and stumbling at lower RPM's.It cranks fine cold. Cold or warmed up when overdrive kicks in it stumbles bad below 40mph. I down shift it to "D" for a 4 speed and it runs a little better. I can shift it back to overdrive above 60mph to use it again. I replaced spark plugs/spark plug wires and distributor months ago. No "check engine " light appears. Fuel pump was replaced 6 years ago. I am seeing an oil leak that was not there before. No oil coming from filter or drain plug though..Seems to be "blow back"...dripping off transmission pan..Could not see better due to checking it early this morning with flashlight. Thanks for the help!

Pete

Even if the dist is only a year old, I would look for a bad pickup coil or worn bushing. At lower rpm, the signal is weak causing a rough idle and stumbling.

//2000CAYukon

Even if the dist is only a year old, I would look for a bad pickup coil or worn bushing. At lower rpm, the signal is weak causing a rough idle and stumbling.

//2000CAYukon


Can that be checked with a digital multimeter?
Thanks,Pete

I don't have a service manual handy, but this article talks about weak signals from the pickup coil www.mightyautoparts.com/pdf/articles/tt71.pdf

With the meter on AC volts, you should see between .5 and .74 volts cranking the engine over.

A bad EGR valve can also cause a rough idle and low rpm stumble.

//2000CAYukon