Occasional miss, comes and goes 94 3.8

I have a 1994 Olds Silohouette with a 3.8. It occasionally runs really rough at any speed like it's missing on one cylinder. I replaced the plugs and wires, and no difference. I kept pulling plug wires, one at a time and it appeared that the 1 and 4 coil pack was weak, so I replaced it, and the same thing is happening.

Then I changed the plugs and wires. No matter what plug I pull, it only seems to get a little worse when it's missing.

It doesn't seem to matter if it is cold or hot, it can do it anytime, and do that for ten miles, then run just great for the next ten miles.

Today it was running good, so I hook up the fuel pressure gauge and it was 37 to 40 lbs, and then all of a sudden it started to run bad, but the fuel pressure didin't change. It almost seems like when it runs bad, it's a real bad vacuum leak, but I have looked over every hose I could find, and unplugged it, and held my finger over the place the hose came from, and nothing seemed to change, it just started to run bad. Then ten minutes later, it starts running like a top again.

So today I figure out how to jump A and B and read my codes on my 93 Silhouette

I get a code
21 TP sensor performance.
22 TP sensor circuit low voltage
23 TP sensor circuit high voltage
34 HO2S CKT insufficient activity sensor 1
26 It also reads a code 26, but I can't find anything about this code. Anybody know what it means? I've heard it means insufficient coolant temperature for stable operation. I've changed the two wire coolant temperature sensor. I didn't replace the one wire temp sensor for the gauge as that works fine.

Anyone have any ideas?

Should I try and replace the throttle position sensor, as I read in the manual that this can cause a miss through the whole throttle range.

I've never seen a O2 sensor make a car run this bad before.

I've checked the connection to the O2 sensor, so I guess it means it's bad. But it must be intermittently bad, or perhaps a bad ecm?

Can anybody make sense out of these codes and perhaps suggest a course of action?

I don't even know if these are the right explanation for these codes my van spit out.

Thanks in advance.
Mike

I think I found the problem. A second compression test revealed no compression at all in cylinder #4. I took off the valve cover and found a busted intake valve spring. That explains my miss that comes and goes. Because if I spin the spring that is busted, I can get some compression. That was a real head scratcher. I sure hope it takes care of my miss.

Anybody know where I can find an intake valve for my 93 Olds Silhouette, with a 3.8?

Thank you,
Mike

i would look at junk yard for an intake valve spring surely one has a cracked head for a 3.8 as for the throttle position sensor it sounds like it is shot.i've never done it but i have heard of an air plug you screw in the spark plug hole and put air to it and it keeps the valve up while you change valve seals so i guess you could do this to change the spring. but if you can't find a junkyard that has a spring then a new one can't be that much.but i would also repace the throttle position sensor.

Thanks for the reply Rockwood. The valve spring did take care of my bad miss that would come and go. I didn't get around to changing my TPS yet, but I think I will, because it does seem to have some dead spots when checked with the OHM meter. Other then that, it's running like a champ.
Thanks again,
Mike