1999 Chevy Astro Miss when cold

SAMPHOTO

MEMBER
1999 CHEVROLET ASTRO
6 CYL
2WD
AUTOMATIC
247,583 MILES

Some days. 1 out of 6 van will miss in morning
high humidity & rainy days van will miss for sure.
9 times out of 10 goes away after warm up.
coil has been replaced recently.
doesn't throw off any codes.
fuel pump replaced 2 yrs ago
plugs and wires ok
I'm planning on a compression test
and a fuel pressure test this weekend
possibly a scope check.
any ideas?

2 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

My first guess when you say it is worse on damp days is either the distributor cap or plug wires. You said they were okay. How did you check them?

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Wednesday, November 18th, 2009 AT 10:30 AM

SAMPHOTO

MEMBER
2 POSTS

The plug wires were replaced 6 months ago
after 1 came apart in my hand. New duralast installed

high condensation areas seem to play a part.
I just drove from a heavy fog area and it missed all day. [ 5 hrs of driving ]

>>>It does not miss under acceleration.
It will miss immediately after letting off gas
and while cruising. <<<

Twice it has missed all day. Both times on long road trips. Normally driving around town it will miss for 20 minutes in the morning and run fine after that.
Most other days it will not miss at all.

I have installed a new dist cap so I'll wait and see.

I did not see any cracks in the old dist cap

Ignition module and crank sensor are recent.
`
thanks for your help