Stumbling after valve cover job

All right guys, another follow up. As I mentioned a few posts ago, everything seemed totally awesome. The vacuum leaks were definitely solved, no doubt that there were at least one or two that showed up during my smoke test that were solved by the silicone vacuum lines that I purchased. However, there was still one symptom that occasionally popped up. Today, I believe I've solved the issue once and for all. Time will tell, and I will follow up.

Anytime that I was on the highway going somewhere between 40 and 60 cruising in overdrive, if I started to go up an incline where the motor needed more power, a stutter would occur. It almost felt like a transmission stutter, as though the truck was trying to downshift to get more power. I did a search and found a thread where somebody had the same symptom, and there were directions for testing the transmission by lightly applying the brake. There is a sensor that you activate with the brake pedal that would stop the stuttering if it was in fact transmission related. For me, the brake pedal didn't stop the stuttering.

In that same thread, it was suggested that the issue could be either coil related, or potentially a faulty spark plug with a crack in the insulator.

By now a little frustrated to say the least, I bought a new set of spark plugs, as well as coils. My plan in doing the job was to take out the spark plugs one by one, and inspect them for possible damage. Turns out, my number four plug did have a crack that ran vertically on the insulator! This was the best news ever, because it seemed to indicate what My running troubles were being caused by. I skipped installing the coils because the crack in the plug is definitely worth playing out. I will return the coils. I buttoned everything up, all new spark plugs in place, and then I went back out to my default test place where I was able to replicate the stuttering multiple times during diagnosis. No more stuttering!

I am not sure what happened to cause the crack in the spark plug that I had installed. The crack was so subtle that it only appeared when I rubbed my dirty fingers across it, and the dirt got caught in the crack. My guess is that it was already cracked when I got it, or potentially that it was cracked during transit. Suffice to say, I gave each of the new spark plugs the greasy finger test before cleaning them and applying fresh dielectric grease.

Im Happy to admit that part of my repair was faulty if it means that the community gets to learn. I hope this thread helps somebody. I will check back in in several hundred miles to confirm that everything is good, but so far so good.

 

Good idea but you may run into trouble come smog check time in CA, especially if they look under the hood.

 

After 600 miles driving to the Sierras this past 4 days, I can confidently say the problem is 100% solved. Thanks for coming along for the ride, hope this thread finds the people that need it.