95 Corsica 2.2 4 cyl currently at 218,000K

Car details from ad online, bought in sept at 211K and
been driving >1000 K a week since.

New exhaust (catyletic converter, muffler, etc.) New
oxygen sensor, new spark plugs, new spark plug wires, new pcv valve, new thermostat, new serpentine belt, new head gasket, new battery, new alternator, new starter, new brakes, new calipers, New Suspension (front struts and strut mounts and rear shocks and shock mounts) New wheel bearing, New tie rod end, new ball joint, K & N Air filter.

Fluids are good, oil was burning in frequent aggressive
highway passing - approximately 1 litre of oil per 200 K. Oil last's 10 times longer since adding 250 mil of
Rislone Oil Treatment.

Question 1 - Engine Stumble

The car runs well and gets decent mileage, tends to idle
a little rough at times - engine tremble/bogging. At a
constant speed between 60 - 90 Kph the car stumbles,
never dies and can be remedied by accelerating as driving at 100 or greater does not seem to have any problems and the car rides smooth.

-K&N Air Filter seems a little oily, there was oil and
sweat inside the air filter compartment.
-Throttle Body had black tar around throttle plate, tried to clean it with throttle body cleaner - still dirty past the plate into the two tubes inside the housing.

Not sure what next to rule out, I hope to do a compresion test to see if it is rings are worn.

Can send pictures via email if it helps figuring it out.

Thanks
rayandjenny@rogers.com

 

I've had pretty good luck with high mileage vahicles using CHEVRON Techron as a Fuel injection / valve cleaner. Just pisk some up and add it to the fuel for a few tankfulls. The stuff is amazing for high miles.

 

Thanks for the tip, turned out to be poorly seated spark plugs. I was pretty shocked to see that the #4 plug was only half threaded. Ended up re tapping the hole with a grinded used plug.

Thanks
Ray