My engine has a rough idle why?

There are two common problems with your truck. The intake manifold leaks coolant into the intake runners or you have a bad fuel injector. These guides can help us see why you have a rough idle.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Please run down these guides and report back.

rough idle when cold. runs great when hot. have replaced engine coolant sensor and maf unit. got any suggestions? codes are 171,174, lean fuel mix.
mike

Lean fuel condition could be caused by one of the following guide:

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

thanks, my intake gasket was leaking I replace it now the truck runs good again. Great site btw.

I have noticed the rough idle for awhile and just now noticed when i start it up i puffs black??? i have changed the spark plugs, changed the oil and i am going to seafoam it this weekend. it is hard to start sometimes, never in the morning it always fires right up after sitting. when i say rough start i mean, i turn the key over and let go it still tries to crank and wont start so i give it some gas while cranking itand its starts.... like a diesel with the black smoke haha, if you could giveme some ideas to check i would appreciate it, thanks

Hi, I would check a couple of things, one is for a leaking injector or faulty injector, another possibility would be a bad fuel pressure regulator, and a dirty fuel filter.. . you must also before doing any of these things, check the fuel pressure and spark. ill send the links to show you the best way to check
joe

https://www.2carpros.com/how_to/how_to_test_an_ignition_system.htm

https://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

recently I had a battery malfunction on the auxilary battery of my dual battery system. I had to jump the battery to start, after replacing the battery the idle was rough in gear only. I cleaned the fuel system & changed the fuel filter & the spark plugs. I also cleaned all of the cables & terminals of the batteries but still have the problem of rough idle in gear. batteries are holding their charge. PLEASE HELP!

[quote:3e2efee0ef="matt m5"]Engine problem
2003 Chevy Silverado V8 Four Wheel Drive Automatic 142000 miles
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recently I had a battery malfunction on the auxilary battery of my dual battery system. I had to jump the battery to start, after replacing the battery the idle was rough in gear only. I cleaned the fuel system & changed the fuel filter & the spark plugs. I also cleaned all of the cables & terminals of the batteries but still have the problem of rough idle in gear. batteries are holding their charge. PLEASE HELP![/quote:3e2efee0ef]

Hello !!


Vehicles equipped with an engine control module, may require a computer relearn procedure after vehicle battery is disconnected. Vehicle computers memorize and store vehicle operation patterns for optimum driveability and performance. When the vehicle battery is disconnected, this memory is lost, which may result in a driveability problem. Depending on the vehicle and how it is equipped, the following driveability problems may exist:
• Rough or unstable idle.
• Hesitation or stumble.
• Rich or lean running.
• Poor fuel mileage.
• Harsh or poor transmission/transaxle shift quality.
Default data is used until NEW data from each key start is stored. As the computer restores its memory from each new key start, driveability is restored.
Driveability problems may occur during the computer relearn stage. To accelerate computer relearn process after battery removal and installation, specified computer relearn procedures should be performed. See appropriate procedures for specified manufacturer.

good Luck!

Code reader says code 171, 174, system too lean bank 1, system too lean bank 2. How do you fix this problem, and what is the problem.

I had same codes on my 02 Silverado 5.3, remanufactured MAF sensor cleared codes after a couple cold morning starts. Also cleared cold morning rough idle starts. Autozone told me when both these codes come up together it is most likely the MAF sensor, not the 02 sensors that are bad. jackski

Yep, I did all of the fuel injectors runs smooth and has good power.

my '02 1500 just started having rough idle issues.the truck starts fine but when its cold out it cant seem to find a steady idle point. complete tune up done ie..wires,plugs and filters with fluids.i keep pulling codes for bank 1 and 2 running lean. as soon as the truck warms up or if the outside temp is above 50 it runs great. please help...

You have a vacuum leak at the intake gaskets. You need to replace the intake manifold gaskets. The lean codes are from the unmetered air entering around the gaskets. When the engine heats up, the aluminum cylinder heads expand and seals the leaks.

2002 Chevy silverado 4.8 113000 miles rough idle in cold weather I have replace the fuel filter,fuel regulator,fuel pump and maf sensor (mass airflow sensor).Did not help BUT when i disconnect the maf sensor in the cold morning the idling improves and when reconnect it the idling is rough and wants to stall. When the truck is warm there are no obvious problems until the next morning?

[quote:d3f730e774="Gilbert Castro"]Engine problem
2002 Chevy Silverado V8 Two Wheel Drive Automatic 113000 miles
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2002 Chevy silverado 4.8 113000 miles rough idle in cold weather I have replace the fuel filter,fuel regulator,fuel pump and maf sensor (mass airflow sensor).Did not help BUT when i disconnect the maf sensor in the cold morning the idling improves and when reconnect it the idling is rough and wants to stall. When the truck is warm there are no obvious problems until the next morning?[/quote:d3f730e774]

My truck does exactly the same as the one listed above. I have just checked a few simple things but have gotten nowhere. Someone suggested that a water temp sensor or an air temp sensor was bad. Is there more than one water temp sensor. The guage reads properly. I would appreciate anyones help Thanks Ron

I would also like to see a solution to this problem. I have a 2002 Silverado with only 59K miles and have the same issues?????

2002 Chevy Silverado V8 Four Wheel Drive Automatic 138K miles
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Hello. I have an '02 Silverado 4WD with 138,000 miles. Last Friday, I took it in for a routine oil change. Saturday morning, the SES light came on and it had a rough idle (more so as it warmed up) and hesitation. Sunday morning, as it was warming up in the garage, I noticed quite a bit of "soot" on the floor from the exhaust. I had the codes read and it came back with P0131, P0300, & P0171. Could all these symptoms be from the o2 sensor, or could something else be triggering that code? Thanks for your help.

all those problems are from o2 sensor. by you telling me you have soot at tail pipe, means your running real rich. code 171 means o2 sensor reads lean. by your o2 sensor being bad and always telling computer its lean (171) so it dumps in more fuel to try to make it rich, but no matter how much fuel it gives it, the computer still sees lean. do you get it. i hope this helps.

My 2002 chevy silverado idles rough on cold start up and sometimes dies. Once driven and warmed up it will run fine.

Inspect and test the coolant temperature sensor and the idle air control valve then report back-

might want to check the lower intake manifold gasket.very common on these.might want to follow this bulletin.Subject: Cold Engine Idle Misfire or DTCs P0171 P0174


Models: 2002-2005 Cadillac Escalade

1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer

1999-2005 GMC Savana, Sierra, Yukon

2003-2005 Hummer H2 99 through 05 GEN III truck engines may experience any of the following:

A cold rough idle that diminishes as the engine warms up.
Possible DTCS P0171, P0174, or P0300.
Random misfires at idle. The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.

If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.
The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
let me know what you find.

My '02 silverado has a rough idle when started on a cold morning. The check engine light has come on and at times the truck dies out. It idles at 500 rpm? When I idle it to 2000 rpms until the engine warms up, then it runs alright, and after awhile the check engine light cuts off. can you help?

What you first need to do is determine what is causing the check engine light to come on. What I recommend is having the computer scanned at a nationally recognized parts store. Most will do it for free. With the trouble code they get, we will know why the light is coming on and why it is giving you trouble.

Have that done and let me know what you find.

Joe

2003 chevy sliverado 4.3 engine, 42,900miles.1/2 ton pickup. my truck just started missing at idle.now its starting to stall. it runs fine once i am moving at a higher speed. but once i slow down it starts missing, and stalls.it will start right up.my truck was running fine two days ago,5-30-06. I think its bad gas. any ideas?

Sorry for the late reply, my first thought was vacuum leak. At idle, a vacuum leak could be very noticeable at higher rpms, not so much.

You could check for dead cylinder, at idle very noticeable, at higher rpms you might notice lack of power probably not much else.