Hi guys, new here. I couldn't tell which section to put this in, so I'll post here and if it'* in the wrong spot, mods please move it.

I just bought a 1996 Oldmobile 88, with the 3800 Series 2 engine in it (non-supercharged). It has 238,000km on it, which is high, but for a 3800 series, not too high.

Anyway, I've had this problem develop in the 2 weeks I've had it. It seems to run well in general, but once the engine is warmed up, and I've been driving for maybe half an hour or so, if I am just holding a constant speed (either using cruise control, or manually), the car will occasionally start to shake/shudder. Sometimes it only does a brief shudder, sort of like the feeling of hitting a pothole. Other times it will continue until I either give it more gas, or let off the gas. It does not seem to be tied to a certain speed (it'* happened at 120kph to as low as 80kph), or gear (I've downshifted from OD into 3, and it still occurs).

I also intermittently get a check engine light, it will come on for a couple hundred kilometers, and then go off for a couple hundred. I will be bringing this in to get checked. The shaking occurs regardless of if the check engine light is on or not.

At idle the car seems to run fine, but I have noticed twice when accelerating the car feels like it is struggling.

Anyone have any ideas?

If your getting the CE with the odd shake and the code is misfire, then I had this same problem and it was the coil packs. Been great since

Sounds a lot like the thread I started. I can't tell if it is the torque converter, steering or engine. Happens most at low rpms trying to work it' sway up a hill or on accelleration. I'm going to try coils too. Three for $100 or so at NAPA.

I'd pull codes before spending any money especially since many place pull them for free.

I'd go with determining the age of the plug wires and plugs. Pull one and see what it looks like. That would be a cheap fix if t hey have more than 50-60K miles on them.
And get the codes read.