Shuddering on the hiway

97 astro 83,000 miles always a good runner but lately seems to shudder or mis in short bursts when driving on the hiway . I have searched simalar posts could be anything from wires to fuel pump. does it the worst when cruse is on. did a fuel filter first and dont want to start just throwing parts at this thing also when you punch it it goes great. sometimes in the morning hard to keep running for first min or so.
any advice as to where to look first
Thanks

How many miles since the last tune up? At 83,000 miles it's due. AC Delco distributor cap, rotor and spark plugs, and a set of either Autolite or AC Delco spark plug wires. Put a dab of silicone dielectric on each terminal of the cap, inside and out. Don't waste your time or money with aftermarket tune up parts, these engines are very fussy.

Typically the fuel pumps are good for 100,000 miles but... key on, engine off, fuel pump running: Pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the pump shuts off.

Any good ideas on how to replace those plugs? Mine is AWD...and after 45 minutes, I'm thinking, "SOL!" I have seen 2, but I've felt around down there and found at least 5! (I know, I need all 6) The Haynes manual says 'if necessary, remove the wheels/splash shields' It is 'necessary' isn't it?

Jack up the front end by the frame so the wheels hang, no need to remove the wheels. You can get right at most of them through the wheel opening. If there are any that you can't get at, you can get at them from under the vehicle or by removing the engine cover. Make sure you use AC Delco parts, (see post #2).

Thanks again for saving the bacon. You ARE the Master, old or not!

Got ACD's #12's to put back in...it has ACD #88's in it. My mechanic friend (An actual schooled, teaching, saleable mechanic) had quite a time even imagining how to get at them. (The ones we can see don't leave much room to maneuver, so we'll see how the jacking does.)

The owner's manual says the original plugs are good for 100K miles...how can you tell if the replacements are?

Truck, 1997 Astro "W" engine uses AC Delco 41-993 plugs, and they will last 100,000 miles. Don't "experiment" with anything else. Exchange your #12's for them.

Actually, it's an "L"...sorry for my lack of specifitivity.

The AC thing is true, don't use anything else on these engines, I tried NGK and had to replace them a few days later with AC. Ran like a bag of nails with the NGK plugs and I am usually a loyal NGK user.

Well, I saved my experiementing with NGK's for the 'yotas. Got a set of 41-993's, and life is good.

Actually, I misread my VIN, it's a "W" engine code, but something in it is an "L"!

Thanks guys!

Glad you got her going, thanks for posting back. These things are real fussy when it comes to ignition parts, it's best to stay away from aftermarket stuff.

1997 Chevrolet Astro and GMC Safari:

The 5th character of the VIN tells the "Chassis" type: "L" is AWD. "M" is rear wheel drive.

The 8th character of the VIN tells what engine you have: "W" is 4.3L V6 with CSFI fuel system.

97 astro 83,000 miles always a good runner but lately seems to shudder or mis in short bursts when driving on the hiway . I have searched simalar posts could be anything from wires to fuel pump. does it the worst when cruse is on. did a fuel filter first and dont want to start just throwing parts at this thing also when you punch it it goes great. sometimes in the morning hard to keep running for first min or so.
any advice as to where to look first
Thanks



Replaced the battery and problem gone (guess sometimes you never know)

Hey that is nice to know that the problem is gone. and i hope now it is perfectly working fine. if any problem do let us know.