How do you clean the IAC?

[MarcNJ]

I am still chasing a rough idle on my 2003 tahoe. 5.3. I had a rough idle and badMPG. A few weeks ago. I cleaned the throttle body, cleaned the k&n filter changed the lcv valve and flue filter. My MPG is way up, but I'm still getting a a rough idle. when I cleaned the throttle body I cleaned the IAC hole on the front of the throttle body, but I did not take the IAC out. I think I would like to try that. I have watched a few youtube videos, but most are just replacing it. What do I need to do to clean that out? Thanks in advance for any help.

 

[rockenthebowtie]

Are you getting a check engine light because for the most part an IAC wont cause a rough idle only a low and or high idle might want to spray some throttle body or carb cleaner around the lower base of the upper intake manifold gasket area you may have a vacuum leak there but to answer your question with IAC removed just spray some throttle body cleaner on a rag and just wipe off any carbon build up that may be on the plungger then you can just spray around the pentle and spring area

 

[MarcNJ]

Thanks! I'll try spraying around the manifold first. I know I had those gaskets replaced atleast six years ago with the new kind when my truck was really going crazy and I was getting a check engine light. No lights this time, I went to autozone to see if there were any codes, but they reader was broken.... I just get this rough idle and it's not even all the time. Usually, it is rough, buy occasionally it's smooth.

 

[rockenthebowtie]

Hmm. When was the last time you had plugs and wires replaced.. also maybe even early stages of a failing coil

 

[MarcNJ]

I replaced the wires and plugs about two years ago. This rough idle problem was happening a few months after that, but way worse. The tac would bounce up and down at idle especially with the ac on. I took it to the shop and after a few tries they found that the throttle body was so dirty it was messing with the iac and it fouled up the new plugs. The cleaned the TB and replaced the plugs. Now late into the fall and oer the winter it was idling a little rough, but I didn't get a chance to clean the TB until a few weeks ago. Honestly, I was in a little disbelief that it would be dirty enough to mess with the mpg and idle after a year. Prior to all this I never cleaned it and never had a problem for years. I have not taken any plugs out to check if they were fouled again. I guess i don't want to know that I need three sets of plugs in two years.

 

[rockenthebowtie]

Are you using OEM parts or aftermarket because it does make a difference.. the throttle body should be cleaned out once a year or every 15k miles... let me ask you this does it actually have a misfire or does feel more like a vibration with heater or ac on... I've come across a few qhere the ac compressor is in engaging with the heat on ac switch off due to a shorted hvac control head

 

[MarcNJ]

Im pretty positive when I did the plugs and wires I used acdelco stuff. I'm not sure what plugs the shop used when they replaced them. I'm not totally sure it is a miss. It feels similar to when the compressor clicks on and off, but it's fast like a split second and frequently, bit it does it with the heat and ac on.

 

[rockenthebowtie]

Yeup kinda had an idea thats what was happening... you have 2 issues your ac compressor is going out meaning its starting to seize up when the clutch engages the other is the HVAC control head is engaging the ac compressor even with the ac switch on the control head being off..

 

[MarcNJ]

I know that I should have remembered this, but the compressor has gone out on my truck before that was 6 years ago. They replaced it with a new dealer one. That was like you were describing. I"m sure it could be going again.... If it were clicking on and off, won't the tac move at all? It always steady and usually I can hear the compressor click on. I don't here that.

 

[MarcNJ]

I sprayed carb cleaner around the manifold. I didn't hear any difference.

 

[rockenthebowtie]

No not if its doing quickly as your describing it see if you can get someone to help you just have them drop in drive park brake on and brake pedal applied ac on and watch the ac compressor as it engages to see if you can duplicate it there you will know if is the compressor also try it with the ac switch off on the control head and if the compressor is engaging there you will at least know that the control head is shorted