Rough Idle 2004 Corolla - Toyota Nation Forum : Toyota Car and Truck Forums

billisnice · 01-13-2012, 10:09 AM

155,000 miles Corollas rough idles sometimes. Not bad, but noticeable. Plugs changed about 5000 miles ago. NKG Iridium. Any suggestions? It is not bad enough to set off the engine light.

MasterTecInSTL · 01-13-2012, 01:12 PM

Intake vacuum leak? Dirty Mass Air Flow Sensor? Bad motor mount making it feel rough?

billisnice · 01-13-2012, 01:37 PM

Is there a test to narrow it down some? thanks

Intake vacuum leak? Dirty Mass Air Flow Sensor? Bad motor mount making it feel rough?

MasterTecInSTL · 01-13-2012, 01:48 PM

Well you can easily clean the mass air flow sensor and check the motor mounts for play.

As far as the intake gasket these are bad for leaking on these when cold (a thicker revised gasket is available because of this) and eventually that will cause your check engine light to come on and set a P0171 (Bank 1 lean) and possibly misfire codes but they tend to cause problems like this long before a code is set.

There's a ton of information here about these three things I mentioned. All you have to do is look around.

billisnice · 01-21-2012, 09:04 AM

I took my car to Toyota for a diagnoses. I told them about the rough idle. They said I bet I know your problem? I said what? He asked me if i bough my gas at Krogers in town? I replied, yes. They recommended HEET fuel treatment and sent me on my way without a charge. They have had 10 cars over the last few months with rough idles due to the additives in kroger gasoline.

I will see after a few tanks of gas if the rough idle goes away.

MD1032 · 01-24-2012, 09:18 PM

One thing to keep in mind with these cars is that the HVAC's defroster turns on the A/C. Check to see if you left it in the defrost or foot/defrost position and turn it back to the other side. My Corolla idles unevenly with the A/C on.

Also, buy some throttle body (acetone) cleaner and start shooting it at the vacuum lines and around the intake manifold to check for leaks, especially when it is stone cold (when leaks usually happen). Your car will stall or change RPM significantly if there are leaks while you are doing this.

johnoh · 01-24-2012, 09:31 PM

at 155k, your idle will improve with a cleaning of the throttle body and iac. Pretty easy to do yourself.

billisnice · 01-26-2012, 08:33 PM

Do you have a decent photo of the throttle body and iac location? Thanks

johnoh · 01-26-2012, 08:51 PM

http://matrixowners.com/index.php?/t...idepics-incld/

one small point - in the post the guy uses his gerber pliers to remove the 5-point screws that attach the black plastic part of the iac with the metal part of the iac. That didn't work for me, so I just leave those screws in, and soak the iac with tb cleaner. Idle is perfect afterwards.

If anyone knows where you can get a tool to remove those 5-point screws, let us know.

billisnice · 01-29-2012, 10:36 PM

Why not just spray Deep Creep through the throttle body and iac opening?

hardtopte72 · 01-30-2012, 01:54 AM

Quote:

Originally Posted by billisnice

Why not just spray Deep Creep through the throttle body and iac opening?

Because that will not get you an effective cleaning.

johnoh · 02-02-2012, 11:22 AM

Quote:

Originally Posted by johnoh

http://matrixowners.com/index.php?/t...idepics-incld/

one small point - in the post the guy uses his gerber pliers to remove the 5-point screws that attach the black plastic part of the iac with the metal part of the iac. That didn't work for me, so I just leave those screws in, and soak the iac with tb cleaner. Idle is perfect afterwards.

If anyone knows where you can get a tool to remove those 5-point screws, let us know.

found it. Its a pentalobe bit