I have a 97 Explorer 4.0 OHV engine 176,000 miles.
I have been experiencing a misfire in the engine at idle at any temperature. I haven’t been able to notice if it is misfiring at HWY speeds. The truck accelerates well at any speed and any rpm and gas mileage is consistent so fuel delivery is not a problem and idle rpm’s are fine also. I have no CEL or any codes. I have changed the AIC valve, spark plugs (motorcraft), spark plug wires (motorcraft) about 40k miles ago and intake manifold gaskets. I even used some injector cleaner for good measure and cleaned the MAF with maf cleaner. I took the truck to an auto repair shop and they checked the vacuum system and said alls well. Wires? Coil Pack? EGR valve???? Is there a solenoid that controls fuel flow to the engine? HELP

 

Just out of curiosity, are those the original plug wires? If so, they could have been changed when the last spark plug change was done. That's a lot of miles on the wires.

 

It's been around 30-40k miles on this set of wires.

 

Do you know how they checked for vacuum leaks? Did they use a smoke machine?
How about if you check the PCV hoses for a vacuum leak.
When you replaced the intake gaskets did you replace the bolt gaskets too, if not you should have.
Intake leak problems don't always show with a smoke machine test.

 

Not sure if they replaced the bolts on the intake manifold. the shop does have a smoke machine to check for leaks. I will check the pvc hoses this week end myself.

 

If I sprayed lets say maf cleaner or carburetor cleaner around the vacuum lines and if there is a leak with it cause a reaction with the motor?

 

yes, it should

 

Sprayed carburetor cleaner around all the vacuum lines i can find and no change to the engine speed. I'm beginning to wonder if the coil pack is going bad or the spark plug wires. If there was no spark at 1 cylinder wouldn't make a rich condition and cause a code?

 

While the engine was running and warmed up i pulled the vacuum line off the egr valve and pulled the pcv valve off and the engine idle did not change. is that normal?

 

There should be no vacuum to the EGR valve at idle, but if it is being held partially open with carbon deposits that could cause an uneven idle condition. Make sure the PCV hose isn't cracked or open somewhere.