Help: Sick '84 Grand Marquis
Thank you for making yourselves available. I have a an '84 Grand Marquis 302.
The car has had the same problem for months and all the new parts have not changed the problem one bit. The valves ping under a load or hard acceleration. The engine has a slight miss at idle or any speed (hot or cold). The miss is not with every revolution of the engine. It is just every now and then. My mecanic plugged it to a diagnostic machine and it said it was the new EGR valve. We replaced the new EGR with a newer one. Still the same. I used a blank off plate but this depressed or forced the valve to be pushed open (this was with the older EGR valve) and the computer knew the valve was open. The car would not run at all so I unplugged the pigtail on the EGR and the car ran exactly the same as it always had been. I removed the blankoff plate and installed the new EGR. The car still runs the same as if the old EGR valve was on it or as if the EGR was unplugged.
I removed the base plate and there is no carbon buildup or blocking of the EGR passages. I have checked for a vacuum leak even under the dash. I have a long list of new parts but nothing has changed or effected the original problem one bit.
I have a new exhaust system. I installed a new smog system including the cross over on the back of the heads. New O2 sensor. New fuel filter. New air filter. New PVC valve and filter element. New plugs, wires, cap and button. New alternator.
This is a 302 (5.0) factory rebuilt engine. It was installed 10 years ago. I am the only owner and driver of this car. I have maintained this engine extremely well. The car starts fine and runs fine but there is always that annoying miss (like a hickup) and the car has no power. If you really "get on it" all you hear is valve rattling. On long hills on the interstate I start loosing speed and you can hear the valves floating.
My mechanic says there are no codes other than the EGR. I replaced a new EGR with another new EGR. He charged me $100.00 to tell me it was the EGR. I do not want to pay him $100.00 more to tell me the car still has the same problem it had before I gave him the money. I guess, as long as I have money, he will keep guessing that it is something new that I have already replaced. I know that new parts can be faulty but I am thinking it is a flaw in the brain box. Do these cars have a history of having a malfunction in the Engine Controller? Hey, if my mechanic can guess, so can I.
Please respond if you have any idea what the remedy could be. Nice car. She is my baby but my baby is sick.