[200K on it.

I took the throttle body off last night and thoroughly cleaned it.  I disconnected the battery so the computer can reset and relearn the clean throttle body.

Spark plugs are 2 years old.

I need to change the air filter this weekend, but don't feel that is related to the rough idle issue.

Still having the rough idle issue at stop, in drive, with the AC on.  Put it in neutral or park, no issue, turn AC off, no issue.

Motor mounts are good.

Check engine light is NOT on.

Any other recommendations on what someone with limited mechanical ability can troubleshoot?

ETA-Sorry folks, I pooched the model year, put in my truck's year.  It is an 03 and the I6 motors don't have the MAF until you get to 05 or later.

possible skewed map sensor reading giving incorrect data to ecm, which is then trying to compensate for a non existent problem?

I don't know about Chevys, but if it was a Ford, it would probably be a dirty/sticking IAC

Clean the MAF sensor

No MAF on the Trailblazer.

I did some more digging and it seems there is a cam actuator solenoid that could be the problem.

It should be pretty easy to check.

Right now I am only $6 into this from cleaning the throttle body.  Hopefully I can get this fixed on the cheap.

I had rough idle on my mazda5 few months back, I cleaned MAF sensor, checked air intake filter and the valve - everything was clean.

eventually a guy in O'relly told me to try to put some cleaner into gas tank (I don't remember the brand), and voila - after like 50-60 miles the problem disappeared. Later I spoke with my brother in law, who is mechanic and he said it could be the clogged gas filter.

https://www.google.com/search?q=trailblazer+MAF&client=firefox&hs=on9&rls=org.mozilla:en-US:unofficial&channel=sb&source=univ&tbm=shop&tbo=u&sa=X&ei=W6r_U57kOszGgwS-kYEo&ved=0CB8Qsxg&biw=1366&bih=609











 

the other thing it could be is the signal to the computer that the a/c is on.
does the idle kick up when the a/c comes on? not just the compressor kicking in, but actual idle speed needs to bump up.
the a/c system is pretty independent and there needs to be a signal to the computer it came on. so a pinched wire or something like that could cause it as well.

My guess - you have a dirty Idle Air Control Valve (IACV).  Remove it and try to clean it (internally) but be careful.  You might want to just replace it.

Rough idle can also be an EGR issue.

Did you check for codes?

this was true 20 years ago, but now the engine controller is what turns the A/C compressor on, the switch on the dash is just a request to turn the compressor on, the controller has inputs for high and low pressure as well

vehicles with throttle by wire(like this one) dont have a seperate IAC

Idle has improved, but still rough.  No spike in RPM, just rough idle.

I am going to try some fuel treatment and put on a new air filter.

Going to pick up a code reader thing and see if anything kicks out.  

Still need to check the solendoid.  

If I can't resolve it through those I am probably out of cheap fixes.

They are awesome to have, but if you are only buying it for this problem, don't bother. I have an '05 TB and I can tell you for a fact that if the Check Engine light isn't on, there will be NO CODE.

I had a random misfire a while back, and even though it was missing, no light = no code.