My 85 2.8, 700R4has two problems that i can’t figure out

1. Poor gas mileage

· it is getting approx. 15-19 mpg

1. High RPM when warm

· Normal idle while cold in park
· High idle when warmed up 2-3k RPM in park
It will stumble and/or bog down when the throttle is opened quickly. I have cleaned the throttle body and the IAC valve. I recently replaced the coil, wire and sparkplugs. I have also cleaned the injectors. Recent fuel filter and fuel pump.
Please help any advice is appreciated

 

Does it get up to operating temp?
If it does, you need to do a coolant temp sensor resistence test at different temps. You need a ohm meter, thermometer, & a pot of water. test the sensor at different temps, google "GM coolant temp sensor resistence" for the temp/ohm values.
When the engine is cold, the temp sensor should be close to outside temp. If you know anyone w/ a scanner it'll be easier to test the sensor.

 

Thanks for the advice, are you talking about a code scanner?

 

If the code scanner can read live data, the it'll help you check the cts.

 

what would the max mpg for city and hwy be for the 2.8 anyways?

 

my mom had a 87 ttop 2.8 and it would get 28mpg. When my dad would drive it to work in kernersville which is a 30mi drive apx. he would get 25-26mpg.