Chevy & GMC Vans

hi everyone.
'95 astro, w engine. 219,000 miles. i've owned it for 12 years and 150k miles. so far it's been mostly great. in years past, I have replaced the fuel pump, cpi spider, and put in the egr screen. now it has developed a misfire at all rpm's. it is not a random misfire, very rythmic. the van won't accelerate much more than 30 mph. it feels like i've dropped two cylinders. i checked the plug wires, all were firing. i put in all new plugs. i'm trying to do a compression check, but man is that a b***h to do that. i'm not seeing any overheating problems that would indicate a blown head gasket. i'm thinking maybe burned valves.
what do you think?

tommy wrote:
...i checked the plug wires, all were firing. i put in all new plugs. i'm trying to do a compression check, but man is that a b***h to do that...

How did the old plugs look? Even if it's not the plug's problem, as the new ones don't cure it, the old one might (or might not) give us a hint as to which cyl is being rebelous.


Lumpy of Phoenixia

i don't know very much but i have a couple questions that relate to problem I've had

1. in the 12 years you've owned it have you ever changed O2's
2. have you every noticed and puff from exhaust or anyone else notice it
3. do you have any trouble starting it it any conditions
4. when it idles any unusual odors

It sounds like a major tune up is in order. Replace the coil while you're at it. And check the bushings in the distributor. If they are worn it will cause a miss fire.

Yeah, that's my thought too. With this many miles, spend $50 and replace all the cheap and easy stuff: plugs, wires, cap/rotor. Check the fuel rail pressure too, be sure the pump is running near 100%. I bet just teh tune-up will take of it.

SmilesSafari, you mentioned replacing the coil as well, I never have (154k). Is there only one on the 4.3? Located where? Aftermarket a choice for hotter spot?

thanks for the help.

yes, i have changed the o2 sensor previously. i did the full tune-up last summer before the cali smog check, including a new coil. one plug(driver's side rear) looked oil or carbon-fouled. it was completely filled in between the electrodes. i didn't notice any poor running then. it passed smog near the high end of the limits.
we don't use this van every day, it's a backup. we are probably only putting 2-5,000 miles a year on it as the kids have all grown up and moved away.
i have pulled all the plug wires individually and put in a plug and grounded it to the block. all fired properly.
i think i remember seeing some oil smoke upon startup last year, but don't notice any now. the exhaust smells like stinky cali fuel.

...or, you could swap in a V8....

(how's that, Justice?)

The stock coil can be a problem when they get a lot of miles on them. I haven't changed mine either. It's got 199600 miles on it. However, on this site there have been several ASVers that have had the problem. Also a friend with a Chevy pickup (4.3) just changed his. I don't know of any aftermarket coils that are "high performance" for our application. But there may be. I'm sure that the better known aftermarket name brand coils could be adapted.
The coil is located toward the rear of the right side valve cover. It shares a bracket with the ignition module. Follow the coil wire from the distributor. It will take you right to it.

I changed mine the oil filler tube is bolted to the coil bracket too. The problem i had was mainly in wet weather, at high rpm or starting it took a couple extra cranks. Accel makes a higher performance coil for our vehicles I was pretty happy with it and definitely feels better then a bluestreak standard one

Okay.

i pulled the spark plug wires individually at the distributor and found that there was no change when i pulled # 4. i did a compression check on #4 and it came up good (160#).

the plug did not appear wet. is it possible that there is something wrong in the fuel spider? it's been so long that i changed it, i don't remember it much.

*after further research, i'm thinking that the poppet valve to cyl #4 could be stuck closed. i will probably open up the upper plenum to look at things. can i clean the poppets?

tommy .. i've tried about 3 or 4 different cleaners, some helped a little for a couple of days then i was back to my symptoms. that includes seafoam.

only thing that worked for me (and i'm not a believer in 99% of the delco line, therefore not a delco 'pusher') was 'fuel system treatment plus' part # 88861012

some parts guys will know it as "poppet cleaner", others won't have a clue as to what you're asking for.. so use the name and # posted above ...

let us know how it goes

after more research, i will be ordering a new spider assembly. as i thought about it, i think i had only changed the FPR previously. at 220kms, i could spring for a complete new spider assembly. i'm guessing that one of the poppets is stuck, and 'while i'm in there' i might as well do the whole thing.

the wife says she misses driving the van.........her commuter car is a bmw 323.

success!

i ordered a fuel spider assembly on tuesday and it arrived saturday morning. i took a chance on putting it in in time for work. no go. i was late for work. it took about 2.5 hours. replaced spider, fuel lines, gasket.

fired it up and no more missing. sounds really good. i'm going to drive it today on a parts run before i button everything back up permanent.

tommy

fwiw, i cranked the engine with the old injector on it and the #4 poppet pulled. it was dry.
also, i had some surging when i first drove on the new injector, but it eventually smoothed out and ran great.

Excellent!

Well, I'm back again. My astro began running rough again, I think it started back in November. I did all the tune up things, but it all looked good. One plug looked dry(6) as I was checking things. I felt as though I had dropped two cylinders. I ordered a new injector spider and replaced it. Back to running well.
This injector spider was less than 3 years old, about 19k miles. The #6 poppet valve was all clogged up. I ordered the new one from injector warehouse, it took two weeks to arrive.

I used a new trick I learned. Just after starting the engine, I squirted water on the exhaust manifold and could see which cylinders were cold, and which ones were hot.