Feels like a light miss
 

97 w/ 5.4L

Got pretty cold here over the new year. Got in my Expy this morning started right up as usual but I immediately noticed an extra slight vibration in the steering wheel. No check engine light, just a nice light pulsating feeling in my hands.

Put the truck in reverse to back up and as soon as its in gear with my foot on the break, the pulsating feeling becomes more apparent. Turn the truck around, place it in drive and take off real slow down the road. Motor is real cold as its in the teens right now so I don't push it. As I pick up speed, it feels like the truck is lurching/pulsating with power in and out as I'm heading down the road. It's not a heavy miss, just enough to raise an eyebrow to know something isn't quite right. Didn't affect the drive-ability of the vehicle. Again, no check engine light.

Head up town to do my business and left the truck running outside as it was pretty cold. Got back in, motor is warm so I take it for a quick drive. I get out of town and push it up to 65 mph. Miss has become less prevalent but is still apparent. The lurching with power feeling is also minimized as well.

I go back home. Let it sit for a few hours and repeat same procedure with a cold engine.

Conclusion/findings:

Same vibration in the steering wheel and same pulsating/miss feeling when engine is cold. Take it for a longer drive to ensure motor gets up to operating temp and is hot. Miss becomes less apparent when hot.

Idle never jumps. Sits right as 600 rpm when stopped at operating temp in drive. Never jumped. Nothing unusual with the idle. It's high when cold and first started but drops down as usual as it warms up.

After my 20 min drive I stopped at a stop sign for a while to listen to the problem with the vehicle in drive. I could tell as the engine idled, it would get to one point and the miss/vibration would occur - like one cylinder isn't getting a good spark - and then return to idling smoothly for a few seconds before that same miss would occur.

My own conclusion leads me to believe I am experiencing the symptoms of a failing coil pack. I thought it was funny that it was all of a sudden, over night happening but stuff happens.

Any other ideas? With no CEL, I have no idea which cylinder it could be, but I am happy that when I changed plugs I put the oldest looking COPs up front! Maybe I'll get lucky and have the culprit be cylinders 1 or 5.

Update:

Don't know if this is related but I get a buzzing noise from the intake area after I shut the motor off. Lasts for about 15 seconds. Took a video of it for reference.

In a very short while you will get a check engine light. You have a coil going out. They normally do this when they are cold and have moisture seep into them. Sometimes they will dry out when they warm up and run fine. After fighting with coils going out at the worst times, I wish I would have just bit the bullet and replaced all of them when the first one acted up. Last ones I got were off Ebay and I got 8 for around $65 bucks. First one I got was over $100 for just the parts. It pays to shop around.

Some you can get out without removing the fuel injection rails. Save yourself some future grief and replace them all.

Yup, that sounds like a coil. Just did mine this weekend. If you have lots of extentions and swivels u can get them out without removing fuel rails.... A magnet to pick up the coil screws well help as well.

Pep Boys coils are $37 each....... Worth replacing all of them once they they start acting up. Others likely to follow.....

Good luck.

I'm well aware of the pain it is to change these things. When I did my tune up last March I didn't have the budget to buy a set of 8 coils. My problem at the time stemmed from fuel injectors and a bad wire. Additionally, since I just had over 100k I did the plugs. In short, new injectors, plugs, boots & wires ate up my budget pretty quick. You both are correct about doing all at the same time. I wish I did now. At the time I looked at it as a "Why fix whats not broken" and I can tell you that was the wrong decision.

I posted this because up until Jan 1, I had never experienced a failing coil. I know what broken fuel injectors feels like and how a bad wire can cause a misfire after the engine warms up, but never a coil. Although I was confident in my conclusion, I wanted to post before I went out and bought a set of coils.

Lastly, no check engine light yet. I shall see...

Mine had a miss and the CEL never came on..Had it scanned a autozone and it had a code stored. It ended up being #3 coil. Might want to scan it just to see.

Did that this morning. No codes found.

I know what broken fuel injectors feels like

What does a broken/bad injector feel like? I ohmed out all of my COP's and they are all within spec and very close to each other... Now thinking might be an injector over a COP... Frustrating...
Thanks