'88 Chevy 1/2 ton, 305 stalls when stopped.

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it's the knock sensor.... it's pretty important as it helps control ignition timing. on the first WOT the ECM initiates a knock event to check the sensor. if the knock sensor doesn't respond, the timing is yanked waaaaaay back to protect the engine, promptly killing most of your power.

your base timing should be set to what the emissions label says to. you'll also have to disconnect the (crap forgot the proper name for it) timing wire (tan w/ black stripe if memory serves), your emissions label will also tell you where to look for it, should be under the relay cover in the engine bay or behind the passenger side kick panel.

late and hard or just hard? probably throttle valve sticking in bore.
HTH, Bret
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it could be your lockup switch in the trans
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Sorry I haven't kept everyone up to date but I've been exhasted at the end of the day.
First, thanks for the advice, but what's a lockup switch? It sounds like a good possibility - I've been thinking this seems transmission related.
Currently the truck seems to idle just fine, even when I'm stopped and in gear, the rpms get pretty low sometimes, but it doesn't die. It now stops almost every time I let off the gas, after accelerating from a stop. Here's what I've done so far:
New O2 sensor New timing chain and gears Changed out ECM for one from the junk yard. Same for electronic spark control, distributor and coil. New idle air controler. New knock sensor (real tough to get the old one out!!!) New possitive cable on battery, old one was getting corroded near starter. Rebuilt the fuel pressure regulator. Removed and dismantled throttle body. Throttle position sensor tests out fine. Twice. EGR system tests fine. Moved the idle stop screw so that it idles a little faster. Checked timing, but I need specs and procedure - book is weak on this because it gives procedure but no specs. There is no info sheet on truck. Also wish I knew how to set the idle speed correctly.
I'm thinking of replacing the fuel pump and fuel filter, but I'm really at a loss. I've either replaced or tested everything that anyone has suggested - except for this lockup switch. I'll try looking it up.
Any other suggestions? I've got to take this in tomorrow if not. I'm tired.
Thanks everyone!!!
snipped-for-privacy@webtv.net wrote in 2275.public.lawson.webtv.net:

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. Dan, REMOVE the EGR valve, clean IT and the Plenum.
It can be "operational" and still not be sealing. Sounds exactly like the correct symptoms.
(for some good second opinions on that) Start a new thread in this NG with a new post. Include in the "Header" . "Experts Needed", and you'll see some new nics reply to your post.
Stay away from the intangents of the symptoms. List only the one symptom and ALL the remedies and repairs you've performed. Do it in a line format, and don't add any spew to the thread.
example...
SYMPTOMS: dies at stops after deceleration idles fine on start up engine runs good under cruise
REPAIRS: A) B) C) etc. etc. etc......
Scribs Abell (are you) . Re: '88 Chevy 1/2 ton, 305 stalls when stopped. Group: alt.autos.4x4.chevy-trucks Date: Wed, Oct 1, 2003, 4:06am (CDT+5) From: snipped-for-privacy@hotmail.com (Dan)
Sorry I haven't kept everyone up to date but I've been exhasted at the end of the day.
First, thanks for the advice, but what's a lockup switch?
It sounds like a good possibility - I've been thinking this seems transmission related.
Currently the truck seems to idle just fine, even when I'm stopped and in gear, the rpms get pretty low sometimes, but it doesn't die. It now stops almost every time I let off the gas, after accelerating from a stop. Here's what I've done so far: New O2 sensor New timing chain and gears Changed out ECM for one from the junk yard. Same for electronic spark control, distributor and coil. New idle air controler. New knock sensor (real tough to get the old one out!!!) New possitive cable on battery, old one was getting corroded near starter. Rebuilt the fuel pressure regulator. Removed and dismantled throttle body. Throttle position sensor tests out fine. Twice.
EGR system tests fine.
Moved the idle stop screw so that it idles a little faster. Checked timing, but I need specs and procedure - book is weak on this because it gives procedure but no specs. There is no info sheet on truck.
Also wish I knew how to set the idle speed correctly.
I'm thinking of replacing the fuel pump and fuel filter, but I'm really at a loss. I've either replaced or tested everything that anyone has suggested - except for this lockup switch. I'll try looking it up. Any other suggestions? I've got to take this in tomorrow if not. I'm tired. Thanks everyone!!!
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The problem was the EGR valve! The way I found it was a bit strange, but I won't go into that, just to say I should have listened to Scribs. Thanks Scribs.
Thanks to everyone, Dan

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And Ed too, he mentioned it first. Sorry Ed.
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