Help I have a 1985 buick Park Ave. It has HEI ignition si is different than most cars on this forum. It is hard starting after the initial morning start.
History i\ : it has 41 k mile was a 1 owner. I have done the following plugs wires cap rotor o2 sensor fuel filter air filter clean IAC clean throttle body clean maf checked timing
2 treatments of seafoam thru the intake and it was driven 900 mile to my house with 3 cans of techron fuel additive. I have also changed the transmission fluid and filter.
It has a poor idle like a miss but it is not missing. around town mileage is 13.5. The mileage over the 900 mile trip was 20 mpg
After having fixed all of the above the MPG is no better and the miss/ poor idle and hard start is still the same. I also cheched for vacuum leaks with a guage and checked for gas at the regulator on the fuel rail > I also checked the egr valve and changed the pcv valve. I have no codes and have checked and cleaned grounds and battery cables,
I also took a new coil and tried it with no change.
help what next ?

JOHN

Seeing you have a classic RWD your problem may be better served in that section.

Moved accordingly.

Have you checked the timing with a timing light?

This is a FWD car and more like the 87 to 91
can it go back to that forum please

being a 307 old engine, its more related to the rwd engines.

have you checked your fuel pump pressure?

for some reason i swear he had a riviera, oops.

after re-reading ur original post, i see you have already checked for fuel, but did you check the pressure? or just the presence.

but what was the mileage before. it doesnt really seem that bad. 20 mpg in a car that has 23 year old technology, doesnt seem that bad to me. plus cold weather will always hurt ur mpg.