03 astro Rough Idle

03 astro Rough Idle

Postby metal4lyf55 [OP] » July 7th 2012, 5:16am

Van Idles very rough in gear when stopped at a light. With the A/C on its even worse. I checked my fuel pressure and its at 60psi with the engine off. But if I start the van the pressure flutters from 45-60psi very fast. I spoke with a couple GM guys that told me that even with good pressure my pump could still be bad. So I wasted 300 bucks today on a Delco Pump and its still the same. Has anyone here had luck figuring this out...Please Help :screaming:
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » July 7th 2012, 5:22am

sorry for the double post I thought it did no work
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Re: 03 astro Rough Idle

Postby Corsemoto » July 7th 2012, 5:54am

Hate to say it after the fact but I wouldn't blow that kind of dough without being sure or more diagnoses. You can try cleaning idle air control valve, throttle body, MAF sensor (with mass air flow sensor cleaner so as not to damage) and look for vacuum leaks, etc. Check your pulleys and tensioner too.
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Re: 03 astro Rough Idle

Postby Jasen » July 7th 2012, 6:55am

Adding to Corsemoto.

What condition is the dist cap in. The dist cap is probably one of the weakest links in these vans. Cheap caps don't last long, aluminum terminal caps tend not to either. Cheap caps get hairline fracture's, base's not flat, both cause in arching. Many of use spend the $ for brass terminal caps, as well as getting the best ignition parts we can.
When was your last full tune up, fuel filter, have you run any fuel system cleaner through it.
Then there's the injector spider.
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » July 7th 2012, 7:04am

You are so right. Just got a little frustrated. I already cleaned all those things (IAC,MAF,Throttle Body) and recently replaced almost all of the vacuum lines...it never got any better. I even pulled the upper plenum to check for fuel leaks and replaced all the plenum seals. Cap,Rotor, Plugs and wire were all done about 6 months ago when this started.
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Re: 03 astro Rough Idle

Postby Jasen » July 7th 2012, 7:11am

Bad cap, busted plug or cracked insulator?

I battled a miss fire for a long time that turned out to be moisture in some of the engine wiring harness plugs. A blast with WD and air, sealed them up with dielectric grease and all was good again.
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Re: 03 astro Rough Idle

Postby Jasen » July 7th 2012, 7:15am

You could pull the dog house off tomorrow evening, then go fire it up in the dark and mist everything with a spray bottle of water and see if you can make it worse.
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » July 7th 2012, 5:24pm

It was not completely dark but I have done this while I was looking for a misfire. I pulled each plug wire at the cap to see if it made a difference. the only thing that seemed strange was when I pulled the coil wire at the coil and turned the motor it arced through the insulator to the frame of the coil body but when I put the wire back it seemed to go away. I did that because when I looked at the coil it seemed to have hot spots on the body of the coil (windings). I suppose it couldn't hurt to do this at night to get a better look. I looked last knight from under the hood but saw no arcing. Did I mention it smoothes out if you give it just a little throttle.
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Re: 03 astro Rough Idle

Postby Jasen » July 7th 2012, 5:29pm

We've seen the arcing coils here before. They get pretty cooked sitting up there in the tight motor bay and can crack. I recently put a Accel coil in mine.
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » July 14th 2012, 8:52pm

still not getting anywhere. I noticed my idle drops from 600 to 500 @ idle in gear with the AC on. I can hear my IAC moving but does not seem to be compensating for engine load.
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » July 14th 2012, 9:24pm

Hey guys I also noticed when I press on the brake it gets worse??The harder you press the worse it gets? does this mean anything...
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » July 15th 2012, 2:34am

any ideas guys???
Also did the night run test but saw no fireworks.
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Re: 03 astro Rough Idle

Postby rabidweasel0912 » August 9th 2012, 8:43pm

Hey Metal4lyf55, did you ever get this resolved? My symptoms fit pretty much exactly.
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Re: 03 astro Rough Idle

Postby metal4lyf55 [OP] » November 16th 2012, 1:21am

Still searching for a solution does anyone have a suggestion
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Re: 03 astro Rough Idle

Postby _brad_ » November 20th 2012, 8:26am

Did you ever get this resolved? My symptoms are the exact same and I have replaced the same parts as you.
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Re: 03 astro Rough Idle

Postby chevymaher » November 20th 2012, 12:14pm

I had the same issue with my stock engine. This is my take on it.

A V-6 or any smaller engine for that matter has more idle issues than a V-8 because the cylinder firing is farther apart.
No Gm V-8 idles under 700 rpm stock and likes it. They tend to idle rough.
They are set to run at 700 and occasionally drop to 600.

Yet our vans are set to achieve 589 idle as a IAC test trying to hold 550. And they idle at 500 for long periods before the computer gets off it's butt and does anything. I looked at the live data on mine.
I know, I know, the engineers were trying to do something the engine simply does not like to do. I was a simply bad design, plain and simple.

It is ragged edge what it will idle at, if everything is perfect. Put in the real world. Engines get wear. Computers are not so swift once they age. They are no longer perfect.

I am a hillbilly and speak my mind. This engine is 40 year old design. One of the best GM ever made. 30 years ago they knew what it would do and what it wouldn't. It is capable of alot more than they did with it in the vans.
As was stated in other threads the engineers had their hands tied. They wanted to design a new engine to just to self promote their worth and existence. So they designed the poor thing to run, as it did not want to run. To prove it was obsolete. And we are suffering from it.

A certain bore and stoke engine has a rpm band it wants to run in. Plain and simple. If you move it out of that band it becomes inefficient. I moved mine into that band it likes. And it runs accordingly, no real mystery there. Alot of dirt talk of our engines is the ancient design and weight comparing them to the LS style engines.
Cast the block and heads out of aluminum as they did the newer engines the weight issue is gone. A decent set of heads that have been in existence for 35 years and running issues are solved. HP to CI is the same as the LS style.
You can't strangle a engine with it's designed heads and cam. And blame the age of the engine. It is the people who designed it.

Mine with it's ported heads and just a touch to big of a cam for a production engine runs great. Competes with the newer engines for power and mileage. Even with the stock computer fighting it every step of the way.
I set my idle up as much as the computer would allow, or it just IAC's it back. 650 rpm they idle like a kitten. Mine idles at 700 as you come to a stop and drops to 650-600 after it sits a second due to the IAC.

The whole :blah: :blah: :blah: of this was to show why they are this way. Compared to everything else GM makes. Idle set speed in the computer is the real gremlin.
:whack: :nono:
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Re: 03 astro Rough Idle

Postby _brad_ » January 30th 2013, 8:50am

Well, after everything I replaced, electrical parts, plugs, wires, cap, rotor, coil, just about every dam electrical part, ended up being #4 cylinder wasn't getting fuel. I was able to see this by pulling plenum off, pulling injector out and cycling the key to prim the pump; no fuel.

Tossed in a new spider injector assembly (got off amazon).

Be sure to check each injector for fuel spray!

Runs great now.
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