Misfire at Idle

LA235105

MEMBER
CHEVROLET ASTRO

I have a 1998 Chevy Astro with 122,000 miles and a 4.3 liter engine. My problem started when I replaced the EGR valve and did a tune up by replacing spark plug, plug wires, distributor cap and rotor plus a new PCV valve. Started missing at idle but went the van is moving it is smooth and if you put a load on the engine like ascending on a hill the engine will spit out a code P300. I don't know may be I did something wrong or missed something? Please help, love my Astro Van.

1 Reply

KENVCR

MEMBER
105 POSTS

It sounds like you may have 1 spark plug wire out of order. Go back to your wires and make sure you have them all in the correct order of firing sequence.
Then check to make sure that the boots are on the spark plug 100%. You should feel the click when it goes on properly.
Hopefully you used AC Delco spark plugs as they are the recommended plug for the van.
The firing order is 1 6 5 4 3 2.
The #1 plug is on the drivers side at the front.
If you are positive that the plug wires are on correctly and the van ran great before you did the tune up, then go back to each spark plug. Pull them one at a time and inspect them for proper gap and oily substance. Oily substance is a fouled plug, get a new one. If same problem persists, reinspect your cap and rotor. Is the rotor seated fully? Is it dirty/oily inside the cap? Can you notice any visible cracks? Did you drop it all or any of the parts? Cracks in the distributor cap will cause this missing/ rough idle.
Good luck and let us know what happens.
Kenvcr