Engine Missing

[kkingram59]

Last year I replaced my 3.0 detec OHC with an engine of the same type with less miles on it but it has a intermitten miss. I've checked the coil pack wires and they read out correctly, changed the egr valve and tube, replaced the cam sensor, and had a mechanic check for vacuum leaks.
A couple of people told me that I needed to get a better ground because that could cause it to miss. It really starts missing bad when I turn on the A/C or heater. On the highway with the air off it does great. Any suggestions would be welcomed.

[taurusrules]

sparkplugs?

[k8crd]

Originally Posted by kkingram59

Last year I replaced my 3.0 detec OHC with an engine of the same type with less miles on it but it has a intermitten miss. I've checked the coil pack wires and they read out correctly, changed the egr valve and tube, replaced the cam sensor, and had a mechanic check for vacuum leaks.
A couple of people told me that I needed to get a better ground because that could cause it to miss. It really starts missing bad when I turn on the A/C or heater. On the highway with the air off it does great. Any suggestions would be welcomed.

I would check the coil packs for external cracks.

[kkingram59]

The plugs looked like they were new and the coil pack is less than a year old.

[taurus2002_taz]

I am having identical paranormal symptoms with the engine miss when a/c is on or defrost is on, at a red light or stop sign. It also chugs and check engine light flashes when I try to accelerate with a/c or defrost on, I'm thinking it is intake gasket related... Do not know for sure though... Will report back with what I find... I'll be looking at the car today I hope...

[taurus2002_taz]

I have used a different IAC (cylinder looking part with a two prong pig tail that snaps in from the side) as well. I hear it when the a/c compressor cycles, but I guess all I can do is ask someone here to take a quick video of what it should sound like when the compressor cycles? I will try to post a video of what my car sounds like...

[knunne]

I have a 2006 SEL with approx 92,000 miles which had the exact symptoms as you describe the code was a P0303. I pulled the spark plugs and they looked great and the gap was in spec. I replaced them anyway since I had the upper intake already off for ease of access.

What fixed the intermittent mis was that I replaced the wires right away. The insulation on close inspection showed signs of discoloration suggesting to me they were grounding out before reaching my plug.

Replace the PCV while you are there but do not remove it until you have the replacement in hand because you break the tabs when you remove it (no way around it).

I used Motorcraft parts since I read a lot of guys were sometimes having problems with aftermarket stuff and I am too lazy to do the job twice to save a few bucks.

Rockauto had everything I needed at a great price (no advertisement just my experience) RockAuto Auto Parts discount codes for approx 5% can usually be found on this site.

Good Luck!

[DaveX 3.0]

Originally Posted by taurus2002_taz

I am having identical paranormal symptoms with the engine miss when a/c is on or defrost is on, at a red light or stop sign. It also chugs and check engine light flashes when I try to accelerate with a/c or defrost on, I'm thinking it is intake gasket related... Do not know for sure though... Will report back with what I find... I'll be looking at the car today I hope...

Flashing CEL is a definite ignition misfire. When you put the A/C on (or defrost, because that turns the A/C on as well), you are putting more load on the motor. So an ignition issue that may not be apparent before will become apparent when more load is put on it. Closely inspect wires, coil pack, and plugs.

You could also use a spray bottle of water in the dark and spray it around the coil pack and plug wires to see if there is any arcing.

[chartmaker]

Originally Posted by kkingram59

Last year I replaced my 3.0 detec OHC with an engine of the same type with less miles on it but it has a intermitten miss. I've checked the coil pack wires and they read out correctly, changed the egr valve and tube, replaced the cam sensor, and had a mechanic check for vacuum leaks.
A couple of people told me that I needed to get a better ground because that could cause it to miss. It really starts missing bad when I turn on the A/C or heater. On the highway with the air off it does great. Any suggestions would be welcomed.

Problem is when AC or Heat is on. Maybe vacuum leak in climate control. You could take the vacuum hose from the manifold to the firewall that goes to the AC and pull it off and plug it. If that makes a difference it is likely a cause. Easy to check.

Old idea. Take the most likely cause, and the easiest to check. Often do the easy to check things, even if they are not top on the list.

Example: anything with PS, air, charging, check the belt.

Just one more idea, even it it is nothing.

-chart-