3400 V6 rough idle at cold start

[Bens71442]

Just started haveing a cold start rough idle in 2002 Alero GL coupe 3400 V6

rough idle GOES away if rpm is increased, (engine smooths right out)

rough idle (goes away) after about 3 to 4 minutes run time, cold to warm up.

it does not run rough after a hot restart

IS this a symptom of a bad Idle Air Control valve?

Only rough run at idle speed cold here

Common someone MUST have had this problem on their 3400 V6 Alero?

[Nate's Alero]

Vacuum leak, bad FPR, clogged injectors, dying fuel pump...anything really

[jayson_waltz]

seafoam it, half thru throttle body the way it tells you to, and half in the gas tank. can't hurt, but if you do have dirty injectors of something it will eliminate that option.

[Bens71442]

It can't be plugged injectors, or else it would run rough continually.

It is a rough run under cold start thru to 1/3rd of the way through the warm up cycle.

This problem clears itself after about 3 minutes run time.

Rough idle goes away after throttle opened to above 950 to 1100 rpm

On COLD engine only

[jayson_waltz]

vacuum is very possible then if the other stuff is elimiated. either that or a sensor on the tb, i have no clue if the 3.4 has diff sensors than my 2.4 so i can't comment much further on here.

[CactusWill]

seafoam it, half thru throttle body the way it tells you to, and half in the gas tank. can't hurt, but if you do have dirty injectors of something it will eliminate that option.


That worked for me, seafoam DOES work. But you need to scan the codes before you do anything.

[Bens71442]

and no Service engine soon light

this is why I'm thinking about a sticking...... Idle Air Control Valve

No One else has had this on a 3400 V6 on their Alero?

Why am I the only person to be experienceing this problem?

[CactusWill]

Idle air control valve *should* throw a code. If it were me, I'd pour a bottle of seafoam through the intake. Worked for me.

[Gr1m]

what do you mean by rough idle? is the car shaking a lot or are the RPMs jumping around?

[Bens71442]

rough engine idle at cold start

rpms not jumping up or down...

if i rev engine and pick up rpm, rough idle smooths out at about 1500 rpm

if I take off, rough idle goes away......

stops idleing rough after about 3 minutes of run time..

I can't get any more specific than that.... it does the above.

New fuel filter today did not do anything to aleviate the problem.

still no SES light

will try the seafoam down the throttle body tomorrow

[CactusWill]

will try the seafoam down the throttle body tomorrow


Seafoam does work, although many on this site would give their left arm for a bottle of GM top end cleaner. Seafoam is much more readily available tho.