Car hesitates while driving, idles high while sitting

OK thanks I'll check the items you listed. However, I did spray around the manifold, and didn't get any idle changes. Also, the TC clutch is disconnected because it was making the engine stall at stop signs, and I haven't had a chance to change it. The hesitation is at speed (anywhare between 30 and 65 mph or so).

No I haven't done that yet. What's the procedure to test it, or should I just go ahead and replace it and the solenoid? Last night driving home (around a 20 mile commute), it was doing its hesitation thing, then the check engine light came on, and the hesitation stopped. Problem with the check engine light, is that my code reader won't read an OBD 1.5, and the Buick dealer wants $60 each time. The OBD 1.5 is kind of an odd ball one, and you can’t jumper it either. Does anyone know a way to get the codes out? This is a "commuter" car that I bought back after I hit a deer with my good car last year, and I don’t want to spend a bunch of money fixing it.

This is an OBD 1.5, not OBD 1, you can’t jump it. It's kind of a high breed between 1 and 2. It has an OBD 1 block, but no B terminal wire. The GM OBD reader will read it (at $60 a shot), but an OBD 2 reader won't. I think it’s an interim step between 1 and 2 that GM did before they went to 2 in 1996(?).

By the way, thank all of you for your prompt and helpful replies! I’m going to donate as soon as I figure this out.

I have a CP9190, and I can't get it to read the codes. Seeing as the hesitation/surging stopped when the check engine light went on, doesn't that point more towards the EGR solenoid?

I'll try it again this weekend. Maybe I did something wrong (wouldn't be the first time). Someone just told me that O'Reilly auto parts might have one that works for free rental.

Again, thanks for all the help!

As it turns out, my CP9190 does work. The lighter outlet in the ash tray doesn’t work, and I didn’t catch it. The analyzer needs 12v power to run the diagnostics. All it said was “connect ADL.” When I connected it to the battery, it worked fine.

So, it’s getting a code 22 “TPS voltage low.” That’s the only code. I reset it, and the check engine light came on while I was driving to work this morning. I’ll check it again tonight when I get home. I changed the TPS back a couple of months ago (my $60 dealer charge that it turns out I didn’t need to pay). Either the TPS I bought is bad, or the pigtail to the connecter has a broken wire (?).

What’s the TPS diagnostic procedure?

Would that cause the surging/missing?

I finally got a chance to work on the car Sunday. Here’s what I did.

I got a 3M fuel system cleaner kit, and cleaned the throttle body, it was very dirty, and ran the TPS tests that hmac300 suggested. The TPS appeared to be OK. The TPS circuit got 5v reference across the power to ground and.4v at the blue to ground. Had a friend operate the throttle, and the VOM showed a smooth voltage up to just under 5v. So because I couldn’t seem to find a problem, I replaced the TPS with a new one I replaced it before when I first got the car, and the part had a lifetime warranty. I then did the tests again to make sure that everything was OK. I found a rotted vacuum line, replaced it, and checked all the other lines. There was a hole in the fresh air hose where the PCV comes in to it, and I patched it with RTV until I can find a junk yard part to replace it. I sprayed carb cleaner on the throttle body, and around the manifold, and didn’t get any idle changes. Then I reset the code (22). Maybe the problem was a loose wire, and, it tightened up when I pushed the pins into the connector to test it (?). Should I replace the plug if the problem comes back?

I test drove the car and the light came back on. This time it was a 32 “EGR diagnostic switch incorrect EGR valve operation.” I reset the code, and didn’t drive again until today. The light came back on. I’ll check it tonight to see what it was. But the car seems to be running smoother and idling better.