I have a 1991 Grand Marquis which until recently needed a tune up - it was
running roughly and lacked power.
I put in new spark plugs, new distributor cap and rotor, new spark plug
wires, new PCV valve and screen. In addition I did an oil and oil filter
change as well as changed the air filter and fuel filter. The timing was set
It runs much better now but there is still a problem. Acceleration is fine
up to about 30 MPH and past about 65 MPH. Between 30 and 65 MPH it lacks
power. If I hit the gas hard it drops into a lower gear. If I try to
accelerate slowly it stumbles and seems to "hold back" - like it is not
getting enough gas. It also detonates under these circumstances.
Can anyone tell me what to do next.
Any help would be appreciated.