Rough idle and hesitation from stop

[pet575]

Ive had the hesitation issue from time to time and it does not happen every time that I start from a stop. But it does seem to be getting worse, especially since the rough idle has begun. I also have slight hesitation when accelerating while in overdrive at speeds over 50 MPH.

The rough idle and slight hesitation in overdrive I can trace back to after I changed my intake. During reassembly, I noted that there is a plug on top of the throttle body assembly near the firewall that did not properly snap back on with the clip. It pushes on but, no matter what I do, it will NOT clip into place. I'm assuming that this is related to my issue and that this plug connects to the IAC valve.

Finally got a code last night when my Service Engine Soon light came on for the first time since the intake was replaced. Code is "0506 IAC System lower than expected."

Does this mean my IAC valve needs to be replaced or is this plug's failure to lock in place the more likely problem? Don't know what I can do about the plug other than replace it.

Thoughts?

 

[tmaher]

bad electrical contact would cause the code to be set. If you can, check the plug and receptacle for any bent or out of shape connectors. this could be preventing proper seating.

If that is ok, clear the code, press the plug by hand and see if the CEL returns. good luck.

 

[pet575]

Code cleared itself yesterday. Still a bit of a rough idle but not nearly as bad as it was. I guess this is a good opportunity to try your "press and wiggle" suggestion to see if it throws the code again.

 

[matt0248]

HAve you cleaned the throttle body? If not you should do so. The '04's have a trhottle-by-wire system that allows the vehicles PCM to control idle speed by opening and closing the throttle body itself. There technically is no IAC on your truck. Carbon-ed up trhottle body bore and blade can cause teh throttle plate to stick and other idle problems.

 

[Sentry6]

Interesting enough, im having the same trouble with my 2002 4.0l real rough idle, and no power from stop, seems to bog down then suddenly build power and take off. i cleaned the throttle body iac and maf with no change... mine has 165k miles but one owner and well maintained... also i notice its alot worse the warmer out it is.... any thoughts?

 

[JoshMcMadMac]

Interesting enough, im having the same trouble with my 2002 4.0l real rough idle, and no power from stop, seems to bog down then suddenly build power and take off. i cleaned the throttle body iac and maf with no change... mine has 165k miles but one owner and well maintained... also i notice its alot worse the warmer out it is.... any thoughts?

No check engine light? It could be coil related. Check for any residual codes, and check the spark plug wells for any moisture down in them.

 

[Sentry6]

no codes... no light... plugs and wires brand new.... weather has cooled off so its been running alot better... strange... still lacking in alot of power of the line but comparing it to my v8 limited....