95 astrovan losing power after ~70 miles

[ZoNiE]

There's less than 70K miles on it. How likely is it the transmission?

Well, it's a GM. And it is a 2004R. About right for one of those, especially since it is 20 years old.

Have you checked your air filter and the air filter box intake for anything that may have been sucked in? A paper towel or scrap of newspaper is all it takes sometimes to starve it for air. That will manifest itself as a sluggish engine.

Your cat could be clogged, check per what was stated earlier.

Also, the 4.3 fuel injection system is common rail, and if there is a pressure loss, it will affect all 6 injectors. I had a 4.3 in a Blazer. Was not my favorite engine. Check for the filter near the engine. That may be your culprit.

 

[Ella1]

Part of the problem is not knowing what questions to ask. I'm taking it in Monday AM. I appreciate all your suggestions. I think I'll have them put on a new air filter, just cuz. I haven't had it changed for a few years.
That bad vibration lasted about a minute,maybe a bit more. I thought I blew a tire, but by the time I thought that, I realized that if I had, at 75mph I'da been in the ditch already. I don't recall any previous instances of it.

 

[debit.servus]

This sounds a lot like the fuel issues I had with the van. Travel some, putter, stall, wait, start-up again, travel some, popcorn kernal pop sound from engine, putter, reduction in speed, stall, wait, try to start if battery is not dead; rinse and repeat. What got me angry is Everybody non-mechanically inclined went "that van is a money pit!", "replace the engine", "it's the vans electrical system".

The van cronicles can be read via the linked thread in my signature.

For OP, is this van from a dealership with service warranty and lemon-protection? If so, have them inspect the entire fuel system, then exhaust system, then electrical system, then engine, then transmission and ask for a detailed written report to share with people you may know who are mechanics.
If not, pay a mechanic or shop to inspect the fuel system; then request a detailed written report to to share with people you may know who are mechanics.

Pro-tip: Many businesses will not return phone calls even for a paying customer, pester them to reply. If you have left 2 messages to their voicemail and they haven't returned your phone calls, on the 3rd call give them 72 hours to return your phone call. If the business does not return your 3rd message within 72 hours, take your business elsewhere. 3-strikes your out. This has to do with the follow up on the written report because sometime the mechanic who worked on your car has gone home for the day and they promise to write your written report tommorow. Keep calling the shop each day for each business day asking for your written inspection report.

 

[Ella1]

I never heard any "popcorn popping" noises. The van is in the shop now, and I'm waiting for the manager to call. Since they replaced the fuel pump relay switch a week ago, it starts better, sounds a lot better, and seems to run better.

There is still a glitch that needs corrected. They are checking the ERG valve. I hope it's that and not the Cat. Converter.
I got the van second hand about 17 years ago. I've been with this mechanic shop for about 5 years and always felt treated correctly, with good (moral/honest) business practices. (The same two mechanics have been there the whole time. Same owner, previous manager retired several months ago.)
He checked the transmission fluid this AM. He was satisfied with it-looks good, no burned smell, so first they're checking the erg valve again, and if needed will vacuum it. THAT was done May last year. I said to him this morning I was beginning to wonder if that "shifting" problem was my imagination, or maybe I'm not using the right words.

 

[Ella1]

I never heard any "popcorn popping" noises. The van is in the shop now, and I'm waiting for the manager to call. Since they replaced the fuel pump relay switch a week ago, it starts better, sounds a lot better, and seems to run better.

There is still a glitch that needs corrected. They are checking the ERG valve. I hope it's that and not the Cat. Converter.

Monday afternoon: I have the van back. They used the motor vac machine, cleaned the fuel system, purged the carbon from the intake system, and cleaned the throttle body. He is sure the cat converter is not a problem. He said it runs well now.
We'll see.
I'm going to have to drive farther/faster than I have been over the last few years. Now that I am feeling better, it shouldn't be a problem.
Thanks to you all for listening and for your input.

 

[Canine]

I'm suspecting you have more than one thing wrong with the van. Very hard to tell what is going on, but a leaking intake or a bad pcv valve could contribute to your problems or possibly something else even. When you fix one problem, don't assume it is completely fixed. Be ready to note possible further issues and inform them to your mechanic. You are doing a good job of whittling this down.

 

[Ella1]

And I will. I will keep a note pad near, and note problems as they occur, and mileage.
I may copy and take relevant invoices in my emergency notebook. It needs updated, so now's a good time.

 

[ZoNiE]

He smelled the trans fluid, but did he taste it?

 

[Almost There]

I'm going to have to drive farther/faster than I have been over the last few years. Now that I am feeling better, it shouldn't be a problem.

Ella, this will sound like a silly question but you've owned this van for 17 years. Have the last few years been only short city driving with no decent highway runs at all?

 

[Ella1]

Ella, this will sound like a silly question but you've owned this van for 17 years. Have the last few years been only short city driving with no decent highway runs at all?

Yes, pretty much. This present time--for about a year--is the first in several years I've been well enough to be ABLE to get out for more than groceries or medical stuff.
Now that I am more able, I want to. Even so, I find it hard to go out the door.

 

[debit.servus]

Ella1
Monday afternoon:  I have the van back. They used the motor vac machine, cleaned the fuel system, purged the carbon from the intake system, and cleaned the throttle body. He is sure the cat converter is not a problem. He said it runs well now.
We'll see.
...

It sounds to me like you have a chararcoal canister. Have the mechanics check for one in the van; and if there s a charcoal canister, ask the people that vaccumed about if it might have burst. My van had a charcoal canister which burst clogging the fuel intake lines. If you can afford it check to see if the charcoal canister has burst