2004 chevy impala, rough idle

Jeff Holshouser

Asked by Jul 04, 2016 at 02:07 PM about the 2004 Chevrolet Impala LS

Question type: Maintenance & Repair

I have a 2014 chevy impala. It has started with this
rough idle here lately. And while driving it will jerk a
little. And during acceleration it seems to hesitate
and jerk a little bit. I've replaced the plugs, wires,
fuel filter, fuel pump, crank shaft position sensor,
mass air flow sensor and I don't hear a vacuum
leak. Any suggestions on this would be greatly
appreciated. Thank you.

8 Answers


If this is a '14 model it was still covered by the new car warranty unless you have over 36,000 miles on it. If it's an '04 model, is the check engine light on? If so, have the computer scanned and post the trouble codes here. Most auto parts stores will do it for free. HTH. -Jim

Jeff Holshouser

It's a 2004. The problem has been going on for about 2 weeks. The check engine light came on. Had it scanned. 0455, evap leak large. So replaced the cap and the vent solenoid. And the light went off. But it still has the rough idle. Don't want to keep replacing parts blind. What about the purge valve or the throttle position sensor

1 out of 1 people think this is helpful.

Check your vacuum hoses, paying close attention to the EVAP system lines. Keep your gas tank between the 1/4 and 3/4 marks to try to get the computer to run diagnostics on the EVAP system again. That's the hardest one to do. Sounds like a vacuum line is disconnected or the purge valve is stuck open. If you have raw fuel in the vacuum line at the throttle body, purge valve is malfunctioning and dumping raw fuel into the throttle body. However the purge valve should trigger the check engine light and a different trouble code should set. HTH. - Jim

Jeff Holshouser

Just changed the purge valve. No difference. I guess I need a smoke test on the vacuum lines. I don't hear any hissing. I'm stumped.

1 out of 1 people think this is helpful.

At this point, I agree. A smoke test will find any leaks, large or small. Please keep us posted. - Jim

Jeff Holshouser


1 out of 1 people think this is helpful.
Jeff Holshouser

And thank you for the help.

1 out of 1 people think this is helpful.

You're welcome. Glad to help! -Jim

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