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Runs rough at idle after warmed up

Tiny
NOVACLONE
  • MEMBER
  • 1994 CHEVROLET S-10
  • 14,500 MILES
4.3 Vortec, 60,000 on engine, just changed spider injection and nut kit, spark plugs, scanned it and shows no codes, starts fine, runs good until its warmed up, runs rough at idle after warmed up, accelerates fine, doesn't miss when rpm's increased, runs fine when driving down the road, new fuel pump and fuel filter about 7,000 miles ago, have not checked egr valve, but did install a egr gasket with the screen awhile back, (maybe plugged?)Right after changing the spider injection and first starting the engine, it ran terrible, but after revving it up a few times it ran smooth, I let it set and run for 20 minutes and revved it put in gear while sitting there and ran great fully warmed up, then drove it around the block, pulled into driveway and when I stopped, it was running rough again at idle. Couldn't find vacuum leaks, cat has never been replaced.I cleaned the idle air valve, and nothing.
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Monday, September 17th, 2012 AT 3:42 PM

7 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Did you clean the throttle body?
Seems problem is low idling speed and it can be due to air flow restriction along idle air control circuit.
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Monday, September 17th, 2012 AT 4:12 PM
Tiny
NOVACLONE
  • MEMBER
  • 23 POSTS
Yes I cleaned everything when I had the top part of the intake off to install the spider unit, maybe bad idle air flow valve?How do you check them?
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Monday, September 17th, 2012 AT 4:22 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Did you look to see if there is any carbon on the egr pindle. Even if you have a screen, it can still prevent the pindle from seating and causing a rough idle.

Roy
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Tuesday, September 18th, 2012 AT 1:55 AM
Tiny
NOVACLONE
  • MEMBER
  • 23 POSTS
After driving it for a couple of days, I was just getting ready to check egr valve, and now all of a sudden it is idling and running fine, hate these kinds of things.
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Wednesday, September 19th, 2012 AT 5:36 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Guess you don't have the problem. The computer has just relearnt your preferences.
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Wednesday, September 19th, 2012 AT 9:02 AM
Tiny
JAMES LINDSAY
  • MEMBER
  • 5 POSTS
I had all the same issues replaced everything, you know what fixed it? The fuel filters are, or must be bad design? Change the fuel filter before it, back pressures and, ruins your fuel pump, I changed fuel lines, spiders, all the injectors, EGR distributor, cap rotor, electric components, you can say, no no no that can't be it? I own 2 Blazers a 1994 and a 1990, they say the ECM, will do the same but, it is rare, for one, to go out, fuel filter.
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Monday, February 17th, 2020 AT 5:26 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
I think the carbon cleared itself from the valve. Very common issue.

Roy
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Monday, February 17th, 2020 AT 5:46 PM

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