My '01 GT has been having similar stuttering problems for 2 months. The
vehicle reaction seems identical to what some of you F150 guys have
experienced ... I'm driving along la la la la at a steady RPM and then I
accelerate on a hill and wham! The car is missing so much that it shakes.
I downshift and punch through it. Every time it happens I feel a pit in my
stomach. And I agree with the dude in the 5.4 miss/ongoing saga thread: the problem occurs at RPMs less than 2500.

The dealer has replaced a transmission mount, the fuel filter and the egr valve. There are no codes coming up and the dealer even installed a data recorder for me. That's how they determined the problem was the egr

I have used gas treatment and for the first few gallons, I really think the
problem subsides ... but it always comes back.

I was actually happy to learn about the COP problems because I thought I was finally on target. I MEASURED THE 8 COILS AND THEY ARE ALL 0.9 OHMS.
Does this mean that the coils are definitely ok?

(Also, the coil connectors are not broken or corroded.)

Oh, and how the heck do you get the COPs off? You guys just say "and then
remove the COP." I tried one ... I took off the bolt, and pulled, but the
COP was snug. I was afraid to yank on it, but I'm guessing that's what I
have to do. (I was pulling on it harder than I would a traditional plug
wire and it wasn't budging.)

My internet research and discussions with some of the guys in my office
identified these possible problems / recommendations:

* fuel system flush

* vacuum leak or fuel delivery problem

* open or shorted injector (injector #1 on my car has body RUST ....)

(I read that at a steady RPM, the computer compensates for a lean injector,
but on high ignition demand a restricted injector is evident ... makes sense
to me. I will check for the click as described in this forum.)

* faulty crankshaft position sensor (not likely as the problem is not
constant)

* fouled plug / shorted plug / cracked plug insulator / misconnected or
corroded plug terminal

* clean air intake to aid sensor performance

* add a treatment to decarb the cylinders

There are so many possibilities ... please help me!

thanks, Kimberly

 

Welcome Kimberly,
This is a truck forum, but we will try to help ya.
Did the dealer drive/ride with the scanner hook up to see if they could catch it doing anything?
I am thinking that under a load, you may be having a COP either losing fire or it is arcing in the plug pocket. You haven't washed the engine have you? they don't run well when water gets into the spark plug pockets.
How many miles are on the car?
I am assuming that the MAF has been cleaned?

Jimmy

 

Jimmy, Thanks for responding. Yeah, I know it's a truck forum, but you guys are so knowledgeable!

The dealer installed a recorder and hooked it up for me to press a button when I felt the stuttering.

I haven't washed the engine.
The car has 32K miles.

I haven't cleaned the MAF, but I will give it a try. If that doesn't work, I'll take it to the dealer for a balance under load test.

I will post any findings.

thanks again.

 

Keep me informed on what you find out.
Jimmy

 

Jimmy, I took the car to the dealer for a balance under load test, but that day, the car wasn't missing. I spoke with a technician and he agreed that I probably have a faulty COP ... he said it's most likely cracked and being affected by moisture. He said I could either bring the car back another day, or he could try to induce the problem by spraying water on the engine. I didn't like the water on the engine idea as that could cause more of the coils to fail ....

I will follow-up after the BUL test.

Kimberly

 

Thanks for keeping me informed.
I'm curious to see what they find

Jimmy

 

... subscribing.

 

Taking resistance measurements rarely provide you with any useful information on a defective coil, unless it is completely open.

The measurements you obtained from the primary winding doesn't tell you anything about the condition of the coil, since the problems usually occur in the secondary windings. But even measuring the secondary resistance generally won't tell you a whole lot either. Secondary resistance readings of a defective coil will usually appear to be quite normal. A resistance reading will only tell you what is happening with a mere 1 volt applied to winding; but it doesn't tell you squat about what is happening when the same coil winding is arcing internally and breaking down while carrying 40,000 volts!

The symptoms you have described, sound consistent with a defective COP. Capturing a scan while the vehicle is being driven under misfiring conditions, should provide Mode $06 misfire counts for each cylinder, pinpointing the offender.

 

Guys, A balance under load test captured a few misfires on cylinder number 7. After coil and plug replacement, my Mustang has been running great for 2 weeks now.

Also, I have the faulty coil and/or plug and I do not see any cracking or indication that moisture could get into the boot. The plug tip is corroded and worn, but that's all I remember. I will post more when I have the parts in-hand.

Further, I have access to failure analysis tools and I've considered evaluating the coil and plug. I can look at the coil using either real-time x-ray or cross-section, but I'm not sure if I would find anything. Any ideas? Does anyone care?

And thanks for helping! I like it when my car runs on all 8 cylinders = )
Kimberly

 

Glad to hear that you finally got it straightened out It could just be a faulty coil that had a minor break in the winding and under certain conditions it may have lost connection internally. It may be one of those things that will never be known

Jimmy