Shaking when ICE is Running, NO Check Engine Light

Howdy, fellas! 2nd Gen 2005 with (I know) 350,000 miles.

Replaced my spark plugs last week, and everything has been running well. Drove to pick up a friend, put her in park, and waited. When we got back out on the road and the ICE started up and I tried to accelerate, the car shook pretty violently, but moved forward.

I pulled back off the road and drove around the parking lot a bit. On electric, it’s fine. But as soon as the ICE kicks on, the shake comes back. It’s slow, but violent when you step on the gas a little. Somewhat disappears when you hit 25, but returns as you let off the gas and let it idle.

No knocking sounds or anything like that, oddly enough.

The bewildering part about it is that there is NO CHECK ENGINE LIGHT.

Ideas?

 

Howdy, fellas! 2nd Gen 2005 with (I know) 350,000 miles.

Replaced my spark plugs last week, and everything has been running well. Drove to pick up a friend, put her in park, and waited. When we got back out on the road and the ICE started up and I tried to accelerate, the car shook pretty violently, but moved forward.

I pulled back off the road and drove around the parking lot a bit. On electric, it’s fine. But as soon as the ICE kicks on, the shake comes back. It’s slow, but violent when you step on the gas a little. Somewhat disappears when you hit 25, but returns as you let off the gas and let it idle.

The bewildering part about it is that there is NO CHECK ENGINE LIGHT.

Ideas?

 

Noted
Alright, I'll read the codes in the morning and get back!

 

Hmmm I’ll look into that! Just thought it was odd—I never even turned off the car, just threw it into park for a few minutes.
Thank you!

 

Alright, update:
Ran the codes yesterday, misfire cylinder 1.
Grabbed some new coils, installed them, checked connections, and she ran fine for about a day.

Today, I was driving a few miles away, and boom. Same problem. So new plugs, new coils, same problem. Just took about a day to manifest.

Could this be faulty wiring? Just takes some time to fry the coil? I guarantee that tomorrow, it’ll start up fine, run through the warmup cycle, then get rough again. After running it, then shutting it off, the misfire exhibits on the following warmup cycle as well.

 

Alright, I know the MAF currently installed is aftermarket. I can swap that fairly quickly. But I would expect other codes associated with the MAF if that was the case.

If it is timing, what could I look at there?
Honestly bummed this happened again—and so quickly.

 

Update! Good because we know what it is, bad because...

Anyways, swapped the MAF, coils, and fuel injectors.
After all that, I finally got the first legitimate sign that it’s what I prayed it wasn’t: a head gasket failure. White, smelly exhaust and coolant in my oil. So sad.