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Rough Idle

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Scan for codes check fuel pressure first. Put vacuum gauge on intake and if 15' or belwo at idle it may be a clogged converter
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Thursday, November 21st, 2019 AT 6:34 PM (Merged)
Tiny
SOUTHBAYRUN
  • MEMBER
  • 2 POSTS
Ok check codes had a random misfire fuel pressure good 54psi until it was running and had a slow leak down, replaced fuel pump but need to remove evap can and can't remove tubing alrdy broke one nipple and have no clue I am depressing the sides of clips but the do not release, what am I doing wrong lol
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Thursday, November 21st, 2019 AT 6:34 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Removal

1. Raise and support vehicle. Locate EVAP canister,  mounted to crossmember or left frame rail,  near front of fuel tank. See Fig. 30 or Fig. 31.
2. Remove EVAP canister mounting bolts. Disconnect EVAP pipes at EVAP canister. Disconnect EVAP vent valve pipe at EVAP canister bracket. Remove EVAP canister. They squeeze together but you need to do this with cannister OFF the truck. It will be either mounted to frame or crossmember. Crossmemeber shown.
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
CHARLES_BEST
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SUBURBAN
  • V8
  • 2WD
  • AUTOMATIC
  • 95,000 MILES
We rescently had a tune up done to correct the rough idle problem. The car idles real low (500RPM and below), but does not stall out. It is real rough at this idle speed. Runs great otherwise.

Our mechanic says it needs a new alternator and battery. Do you think that is the problem. Seems to me that if the alternator was bad, it would create other problems.

Any ideas.

Thanks

Charles
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Is the service engine soon light on? Or the Battery light? If the SES is lit first thing you need to do is have the codes read, Autozone does it free, Post the results with the code number(s). Even if the service engine light is not on, there should be freeze frame data stored.
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
CHARLES_BEST
  • MEMBER
  • 2 POSTS
No check engine lights (or service soon engine lights) have come on.
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Clean or replace the idle air control valve, it's bolted to the throttlebody
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
DAVID QUENNEVILLE
  • MEMBER
  • 1 POST
  • 2001 CHEVROLET SUBURBAN
I have a problem with a slightly rough idle and stalling problem. The truck idles at around 500 rpm. When I rev the motor then let off the accelerator the rpm drops below 500rpm almost stalling and then idles at 500 again. When driving slowly and in parking lots it tends to stall when I let off on the accelerator. It seems to be ever so slightly missing at idle also. On the open road it seems to run fine. So far I have replaced, air filter, spark plugs, plug wires, fuel filter and the throttle position sensor. Still have same problem. The check engine light has not come on at all. Please Help! THANKS.
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
The fuel pressure regulators are very common for a leak and causing your symptoms.
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
ANOTHERVIEW
  • MEMBER
  • 20 POSTS
I am guessing you don't have a fuel pressure gage.

Where I live they are easy to find at Auto Zone, and not too expensive. If you are going to be diagnosing your own vehicle very long, it will easily pay for itself in not wasting money on wrong parts.

It would help narrow down this one.
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Thursday, November 21st, 2019 AT 6:35 PM (Merged)
Tiny
LWR
  • MEMBER
  • 2 POSTS
  • 2002 CHEVROLET SUBURBAN
  • V8
  • 2WD
  • AUTOMATIC
  • 130 MILES
2002 Chevy Surburban, Southern California area, when (cold day) engine is started it idles at 1100RPM for about 30 seconds, then drops to about 600RPM, the engine is rough, service engine light comes on, sometimes will stall, if I hold accelerator down to get to around 1000RPM the RPM will not stay but fluctuate between 800 and 1200, after engine warms up seems to run normal. When started after intial warm up or on a warm day 60 degrees or hotter it still runs a little rough but only for a short time.
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Thursday, November 21st, 2019 AT 6:36 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Could be the idle air control valve needs cleaning.

Have the computer scanned for code/s-you have a problem within the engine management system that caused the CEL to turn on-This is your starting point of diagnosis, finding out what's going on.
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Thursday, November 21st, 2019 AT 6:36 PM (Merged)
Tiny
LWR
  • MEMBER
  • 2 POSTS
The mechanic said it was a generic code that code mean anything. Then he went on to say that my vehicle has a plastic intake maifold which warps that causes a vaccum leak and it could need replacing which costs 5K.
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Thursday, November 21st, 2019 AT 6:36 PM (Merged)

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