Hey guys. I am at a complete loss at this point. My truck has a slight miss that only occurs when certain parameters are met. The truck has to be under almost no load, the throttle must barely be applied, and the rpms have to be right around 2000. If these conditions are met it will make the truck skip and it will dance back and forth between locking and unlocking the torque converter when it skips. Also once it has skipped a few times the idle seems to get much worse.

I have JUST replaced (1000mi>) the following items:

8 brand new coil packs
8 Brand new Motorcraft Sprakplugs
new IAC motor
New TP Sensor
both upstream O2 sensors
cleaned MAF
New fuel filter
new fuel pump
New PCV Valve

I have extensively searched for vacuum leaks to no avail.

I am just about out of ideas and this is driving me completely nuts. If anyone has any ideas at all I'd be very greatful to hear from you. Thanks!

OUMX117

 

I have heard an intake gasket leak can cause an intermittent miss.

 

maybe cleaning the throttle body.

 

Ide take it in and have the motorvac service done. Clean the TB and egr ports. Injectors cleaned as well. And how have you checked for vacuum leaks?

And depending on where you bought your cops (im guessing you have the 5.4L) they have been known to have a few that are faulty out of the box. If you can get it to idle rough, get under the hood and one at a time unplug the electrical connector to the cop's to check for one that does not make a noticeable difference when unplugged. A good cop will when unplugged will make the miss worse. Same with your injectors, you can check them also after you have made your rounds through the cop's. Continue to check for vacuum leaks also

 

After I replaced COPs and plugs this past summer, I had a persistent light miss but it would throw a code for #3 cylinder. After much beeochin' .... it turned out to be a defective spark plug

 

I'll try cleaning the throttle body. I have been checking for vacuum leaks by spraying carb cleaner at any/all the areas I think it could be leaking and waiting for the motor to rev up. Any more ideas?

 

When you clean the TB, pay particular attention to the EGR ports. You may also have a sticky EGR valve.

 

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My mistake. The Motor is a 5.4L and it has 8 new coil packs from the link that you posted. I am going to try to clean the throttle body/egr valve later this week. I'll let you know how that goes. I hope it's not a coil pack. Those things were a major PITA to change.

 

Uhoh - Brew is going to give you a blast for referring to a COP as a coil pack...........don't take it personally.

 

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