Great site. Lots of info.

I have a 1997 F150 XLT 4x4 4.6 engine automatic
I have a custom made dual exhaust system with maganflow mufflers,Intake system,K&N filter.

Ok the check engine light has been on for the last 2 years but I taken it to the dealer about 7 times.They installed new O2,new MAS or MAF,new plugs they cant find anything on it,no codes no nothing just the light that wont go off.

This are the symptoms.

Bad fuel economy,Idle surges,Idle way to low,when you coast to a stop the engine will die and then come right back up to like 1400rpm and then go to the low idle.

Its scary cause when you are stopping at a stop light as soon as you stop,it will accelerate back up and if you are not expecting you might just hit the car in front of you...Well can't describe it better that that I think....

When it started up in the morning it will run so rich that your eyes feel like they are burning if you stand close to it and it has a very slow and heavy acceleration I think way to rich.

Well I dont think this has anything to do but it has 213,564 miles on it.

My question are:

Could the miles indicate a worn engine?
Could I have a bad EGR?
Bad intake manifold gasket?
Bad something?

HELP?!?!?!?!?!

I did check the compression on all cylinders. Highest 210psi lowest 190psi.
I put a new fuel filter,new spark plugs,new wires,clean the throttle,check the tps.

Well that it for now any help I will really appreciate it cause im done here....

Thank's

 

clean the IAC?

 

johngs thank's Ill start with that cause I havent done that

 

Check the fuel pressure. Perhaps the diaphram in the FPR (fuel pressure regulator) has ruptured. Pull the FPR vacuum hose off. Does any fuel leak out? There shouldn't be any on the vacuum side. I haven't seen any Fords with this problem, but I've seen several Chevys. Those stumble a little and are hard to start sometimes when cold.

You may even have a fuel injector that has gone goofy. There are ways to check them on the car or you can pull them out to get checked. After the rail has been pressurized it should hold pressure for a few minutes. If it doesn't hold pressure, one or more injectors is leaking down, and the gas is winding up in the engine. Depending on how long it sits, it may run pig rich at start-up if this is the case.


The miles shouldn't mean much. 4.6's regularly make it to 300,000 miles plus. Mine currently has 252,000 miles, and still runs great.

Good Luck!

 

you also might want to clean your MAF, especially if you have a K&N. I have one and the oil from the filter seems to dirty the very small coils in the MAF. You will need a tamper proof torx to get the back plate off.

 

Concentrate on the IAC as suggested.

If cleaning it does not help, replace it.

Steve

 

How would one clean the IAC (I'm assuming you're talking about the Idle Air Control....valve?) And where is it in relation to the Mass Air....and any cleaning tips would be much appreciated.

 

madnez, possibilities include vacuum leak(s), bad plug wires, leaking egr/bad pcv, bad fuel pump. short circuit/damaged ignition system. make sure the fuel/air filters are in good shape. you may have multiple problems but i keep thinking MAF altho i know you got a new one. bottom line, most likely something in your emissions system (including stuff like maf, egr, iac, vacuum leaks. With high miles maybe your egr,etc are heavily carboned and require replacement), or igntion system (bad wires, defective plugs, etc) or a fuel delivery system. As a wild card, i have head that a bad vapor recovery canister can cause all kind of wierd drivabilty problems. It is located near your spare tire and rear axle. make sure your thermostat is good-i'd replace with a ford OEM i.e. make sure it is not stuck in open. pls post back with your progress.