rough idle,stalling,no restart

[ED MEEK]

have had rough idle for 30,000 mi. At regular idle, seems to have a steady miss. When i run it up to about 950-1000,it runs smooth as glass. Found that when i unplug coolant temp.sensor, it runs smooth but shudders when i race engine and let it come back to idle.
on the no start, i have replaced fuel shutoff, but still the same outcome. can wait a few minutes, then it will light off

help

[ucdavis]

What year rig, model, mods, mileage on rig/components/mods...?
For starters, you may have the infamous Stalling, No Start condition (see: http://www.thedieselpage.com/members/tt99-9.htm ) and you should run thru the checks listed there starting w/retrieving codes (see: http://www.thedieselpage.com/members/trblcode.htm if you have a 94/95 rig or get a local mechanic to do a code scan if it's '96 or later). This has a number of potential trouble sources which the process isolates.
Repost your rig info and any other description that may jog reader's memories for more help.

[ED MEEK]

IT IS A '94 GMC W/125,000 MI. EVERYTHING STILL STOCK. ORIGINAL OWNER HAD 5 IP's REPLACED UNDER WARRANTY. LAST ONE AT 78,000 MI. WHEN I BOUGHT IT,IT HAD MISS AT IDLE. IT SEEMS TO RUN TOO WELL TO BE SOMETHING TOO MAJOR, NO SMOKE, 15 MPG, GOOD ACCEL. HAD IT IN SHOP, BUT ONLY CODE WAS FUEL SHUT OFF. I REPLACED IT, BUT STILL SAME MISS AT IDLE, AND STALLING

[tom.mcinerney]

May have low voltage at idle. Has alternator been replaced?
At idle oil press low, lift pump may not be getting power.
Good connections help.

[gmctd]

If you have not, click the SEARCH button at the top of this page, name your subject, and you'll have all the archival info on this Forum.
See if anything there duplicates your problem, and the "fix".

Pcm will vary fuel to each cylinder as required to maintain steady idle rpm, compensating for a\c compressor loading, and etc.
Could be PCM.

Could be connectors, pinched wiring from many replacement procedures, etc. You will find much info with a "search".