Got a 2000 Grand Marquis. She has 136,000 on her. Clean as a whistle and until recently has been sweet with a smooth power band while accelerating. My fuel economy has also gone to sh*t from about 19.0 mpg to 15 mpg. Only mods I''ve done have been K&N drop in filter and Flowmaster 40 - series muffler. Plugs and wires changed out bout 15,000 miles ago. Same with tranny fluid, fuel filter. Just changed my oil 1,000 miles ago. Check engine light came on this morning. Not much of tool head so if anyone has ideas please let me know. Much appreciated.
- Big Rob

Went to Auto Zone for computer diagnostic. Turns out I have a misfire on cylinder #4. Going to get tune up tomorrow. Plugs and wires. Hope that''s gonna do it.
Edited by: ROBBINFOOLS

Did you get your tune up today?

Have you changed where you get your gas recently? A lot of times a CEL out of the blue can mean bad gas.

Nah, couldn''t get there today. Gonna try tomorrow.

I had a similar problem about a year ago, after I took my car in for its inspection.


When I was leaving the shop, I noticed that it ran like sh*t and after a few blocks the CEl came on. I have a diagnostic tool at home which gave me a code for misfire on cylinder number 7. (I think it was P307)


Of course I tried all the usual tricks like pulling the plugs and switching the plug on coils, without any result. Misfire and hesitation remained.


I then took an automotive stethascope and put it on each of the fuel injectors. I found that the injector for number 7 was not clicking at all. I looked closer and found that that the wire harness for number 7 was broken. (An easy repair).


It seems to me that misfires with the 4.6 are usually caused by an injector problem, and not by the old usual suspects.

CRACKED INTAKE MANIFOLD!!!!! Turns out original factory part is made of plastic! Replacing with Napa manifold made of aluminum. Mother F*ckers!! Comes with thermostat and gaskets. Cheaper than new ford manifold.

yeah... I have avoided considering the newer MGMs and vics because of this. discovered the other day that my mom''s taurus has a plastic intake on that little 3.0 v6. thankfully it doesn''t have any coolant lines running through it and has a heat shield on the engine itself so it should last, less thermal expansion/contraction. I refuse to buy a car with a plastic engine (or any major part of the engine being plastic).

How much was the all aluminum one from NAPA? The stocker on my 96 was all plastic, and the autozone one I replaced it with was plastic with an aluminum water jacket grafted to it. I think it was something like $158

yea... I got that one with the aluminum graft. Damn that pisses me off. I wanted something more rugged. Oh well. The kit was $299. Cars running awesome again. Shouldn''t have to replace that part ever again.

makes me wonder if the 92-94 aluminum intake would fit the later models with the 4.6. my wife''''s 93 vic has the 4.6 with all metal. plastic only starts to appear at the intake hose.Edited by: slymer