rough idle sometimes

[jmathias]

I have a 04 xlt and the other night i went out to start it and it idled really rough, engine was shaking really bad. Turned the key off and it did it again, turned the key off again and it started right up and ran fine. It continues to do this if i start it and it idles bad, if i turn the key off and try it again it will start up and run fine. I have had the IAC replaced a while back and have changed the fuel filter. I also changed the fuel pump relay. Could my IAC be bad again, or maybe the fuel pump. It has me confused since it is intermittent and will run fine sometimes. There is no difference if it is hot or cold. Any suggestions would be appreciated.

Thanks

 

[Tbars4]

...first, welcome here...i know it may sound a little dumb but thoroughly inspect all your vacuum hoses....several times i have found a small break in a vacuum line and resolved a similar problem...i know there can be more reasons for this but it sounds like you replaced a few of them...and don't forget to check the evap lines....have you tried to get your stored codes read???

 

[jmathias]

I didn't have the iac replaced, it was the trottle position sensor.

 

[jmathias]

My service engine soon light doesn't come on either, I checked with the local auto parts stores and they said the only code readers they have don't read stored codes, only current codes when the service light is on.

 

[Tbars4]

...well, your original post says you replaced iac...i take it that you haven't replaced it from your recent post....i would lean to that direction....just a quick question though, does your check engine lite come on briefly when you start the vehicle???....i am just asking this as sometimes the bulbs do go out...

 

[jmathias]

yes the light is ok, my vehicle doesn't have an iac. it is a drive by wire model.

 

[Tbars4]

...well, thats as far as i go....i would still try to get the codes read, look again at the vacuum lines, and then be thinking along the lines of an intermittent short...i'm sure someone will come along shortly with some more input...good luck

 

[jmathias]

The dealership said that I have an intake valve sticking on cyl number 1.
Does this make sense how could they tell before taking the head off? I just don't want to be snubbed by the dealership since this is going to be very expensive to fix.

 

[jmathias]

Broken valve spring, burnt valve, and head replacement.

 

[Tbars4]

...is that what they found??? any chance that is covered on your extended warranty???

 

[High_Order1]

Before they yank all your engine loose, I would look at your fuel filter. That is exactly what I have seen happen in several makes and models. The filter gets plugged up, you let it sit, it will suck up the fuel available and run ok, but then when it tries to push more through the filter, it wil start stumbling.

Now, in addition, you could have the above referenced problem, but I'd check cheaper first.

-Shawn