BUCKING

Sounds like it's misfiring under load. Check for codes in the computer to help you find out which cylinders are doing it. If it's not a misfire, it could be a bad Mass Air Flow sensor.

I HAVE ALREADY CHANGED THE MASS AIRFLOW SENSOR. THE MISS FIRE IS SPORADIC. IT MISSES ON 1, 4, & 6 MOSTLY BUT THERE IS NO RHYTHM TO IT. IT NEVER FOLLOWS THE SAME SEQUENCE. i HAVE THOUGHT OF A VACUUM LEAK BUT CAN'T FIND ONE. I HAVE CHANGED THE COMPUTER AND ITR DID NOT FIX IT EITHER.

No, I wouldn't expect the computer to help that. It's usually collective resistance in the secondary ignition components which are the plugs, wires and coils.

I USED AUTOLITE PLATINUMS TO BEGIN WITH. THEN CHANGED THEM WITH AC DELCO. WHEN I CHANGED TO DELCO I ONLY DID 3 AT A TIME. MY WIFE SAID IT RAN GREAT WITH NO PROBLEMS WHEN IT WAS JUST THE FRONT 3. AFTER I CHANGED THE BACK 3 IT STARTED ALL OVER AGAIN.

That tells you the problem is in something you did with the plugs and wires. Check your firing order again. You also may have cracked a plug. You didn't mention wire. Make sure they were changed with Motorcrafts.

WHY WOULD I USE MOTORCRAFT ON A GM. I CHANGED THOSE ALSO WITH DELCO FROM THE DEALER. I ALSO DIDN'T SAY THAT ONE DAY THIS PAST WEEK SHE TEXTED ME TO ASK WHAT I DID TO THE VAN BECAUSE IT RAN PERFECT THAT MORNING. THAT AFTERNOON IT WAS RUNNING BAD AGAIN. I WORK AT AN AUTO BODY SHOP SO I GET GREAT DISCOUNTS, LIKE YOU.

My bad, I forgot it was a GM.
You're going to have to track down which cylinders are doing it and find out why.

IT IDLES FINE AND CRUISES FINE AFTER GETTING UP TO SPEED. THE FUEL ECONOMY SEEMS TO BE DOWN THOUGH. I HAVE WONDERED IF IT COULD BE SOMETHING IN FUEL DELIVERY OR SOMETHING WITH THROTTLE POSITION.

I HAVE HAD IT AT A REPUTABLE REPAIR SHOP IN MY AREA ONLY TO HAVE THEIR MAIN MECHANIC BE JUST AS STUMPED AND SCRATCHING HIS HEAD AS I HAVE BEEN. I KNOW IT IS THE 1 4 6 CYLINDERS IN NO PARTICULAR ORDER. IT JUMPS ALL AROUND WHICH ONE IT MISSES ON WITH NO SEQUENCE TO IT.

You might want to have the fuel injectors pressure cleaned. They could be all varnished up.

HOW DO I DO THAT? I USE LUCAS FUEL TREATMENT IN IT REGULARLY. I HAVE ALSO TRIED THE SUPER STRENGTH LUCAS. I HAVE HAD BG RUN THROUGH A CAR I HAD A LONG TIME AGO TO REMOVE CARBON. COULD THAT BE A POSSIBILITY? DO YOU HAVE TO REMOVE THE FUEL INJECTORS TO PRESSURE CLEAN THEM?