1999 Astro misfires after 3 months of storage

[mpmahan]

After 3 months of outdoor storage, my Astro van was very hard to start. Once it started running it was very rough. I hooked up my diagnostic reader and it indicated that cylinders 2 and 3 were misfiring. After half an hour of rough idling in the driveway with no improvement I turned it off. Later in the day I tried it again and this time cylinder 6 was misfiring and 1-5 were OK when idling. As rpm was increased to 2000 cylinder 6 stops misfiring and cylinder 1 starts to misfire. I took it out on the road around the neighborhood but the misfires on 6 continued at low rpms and 1 misfired at higher rpms. It ran fine before storage and only has 50,000 miles on it.

Is this a fuel gunk problem or poor electrical connections? Is there a sensor that I should monitor with my diagnostic reader?

[ASTRODRAGULA]

I do not have extensive knowledge on 4.3's but just goin back to basic engines ..//? Have you looked at distributor cap and rotor. Thats just what came to mind when i read this. Just tryin to help brainstorm

[ASTRODRAGULA]

Or fuel Filter Or that nasty fuel gunk thing in your tank My beer, coffee, and gasoline are three things not to water down

[Blue Bowtie]

Welcome Aboard!

I suggest the "ZombieAstro" is correct, and your diagnosis should start with adding about 5 gallons of fresh, low octane fuel. Low octane is more volatile, and will help dilute any stale gasoline better, and a lower octane ethanol blend might be even better. Allow time for the fuel to work through the system.

Once the question of stale fuel is resolved, your diagnosis can continue. The fact that the misfire is random and not consistently at any given cylinder(s) under different conditions sounds more like a fuel delivery or mechanical problem than ignition.

[mpmahan]

Low octane fuel didn't make a difference. Drove van more than 15 miles at all speeds and there was no change in performance. I think that it's only cyclinder #6 misfiring and my diagnostic reader is incorrectly reporting #1 at rpm's > 2000 - the switch over is very repeatable and the vehicle performance doesn't change during the acceleration through 2000 rpm.

It seems like a bad/loose plug wire, a fouled plug or a clogged fuel injector......is there a web page with engine cover removal instructions and that shows the location of cyclinder #6?

[old_master]

Engine cover: 2 torx screws hidden under caps, towards the top of the trim cover on each side. 2 bolts and 2 nuts (13mm) next to the heater floor register. 2 bolts, 15mm socket with a long extension, hold the cover to the bulkhead. Remove the electrical connectors and heater duct.

Odd # cylinders on the driver side, evens on the passenger side. Cylinder #6 is the rear cylinder on the passenger side.

[Blue Bowtie]

You may also have a storage compartment, CD deck, drink tray, and several wire connectors to remove before you can get to the actual cover.



Once all that and the heater duct that MT mentioned is removed, you can get to the two rear screws and loosen the two from under the hood:



Then you'll be home free. Be patient removing the cover, since even with both seats fully elevated and moved to the rear, it barely fits past the passenger seat and must be tilted slightly then twisted out of the space before it can be lifted clear:

[mpmahan]

Thanks to everyone for all of your suggestions. After changing the distributor didn't fix it, I took the van to my local mechanic. Everything checked out OK except for the fuel injector. He then reminded me about the 10 year 100,000 GM special warranty - C99066B - service engine soon light with rough idle. So, I took it to the dealer and they replaced the faulty injector at no cost. Now it runs like a champ. All is well.

Once again, thanks to all who helped further my education in automotive repair. This web site and forum community is great!!!

[ericn1300]

that 100,000 mile warranty is a California required emmisions warranty, not aplicable in all states. i heard that California is trying to push the emmisions warranty out to 200k since cars are lasting longer.