Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hey everyone.

I had the SES light come on the other day, took it to AZ and had them run a check on it. Codes were Thermostat (opening too soon) and MAP sensor (I was told most likely caused by a dirty throttle body).

Well, yesterday I replaced the thermostat (WOW! Didn't know what I was getting myself into)....of course, I removed the alternator to do it. Got everything back together. Ran out of time and didn't get the throttle body cleaned, I plan on doing it today. But afterwards, whenever I would turn on the A/C it would start to stall everytime the compressor would click on, then it would come back, then stall, back, stall...over and over again. It only happens when idleing or sitting still in gear, if I'm giving it gas, it's not a problem.

From what I've been able to read, I think it's just that I need to do the whole "disconnect battery, clean throttle body, reconnect battery, drive a while" routine.

Just looking for some affirmation/clarification on this. I'm heading out of town tomorrow and really need to try and fix it today. Praying it's nothing more serious than this.
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
99% chance that's all it is. It's such a miracle cure that folks are astonished.

As to why it got worse after the thermostat work - you must have disconnected the battery. Then the PCM loses its adaptive knowledge of how to deal with the dirty, sticky throttle body, and for an hour or two it will run poorly. When the throttle body is really dirty, it can't adapt enough, and then the idle is badly affected by the AC compressor load.

After you disconnect the battery to do the throttle body, expect a short time of rough running as the PCM relearns how much it needs to open the butterfly valve to get a certain RPM. Once it relearns, it will be so smooth you'll think it's a new engine.

Reminds me I have to do mine this week, too. Been 30K miles and that's all it takes to gunk mine up.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
Thanks

Thanks a ton, roadie. I was pretty sure that was going to be it, but I'm still a novice when it comes to automotive work. I've always been intimidated by it, but finally started to tackle my own repairs and save a little cash.

Anyway, thanks again!
 

·
Banned
2003 gmc envoy_slt
Joined
·
7,190 Posts
:tiphat Welcome :tiphat .Just replacing the t-stat and cleaning the throttle body yourself saved you more than a little money.
 

·
Registered
2002 gmc envoy_slt
Joined
·
3,203 Posts
Yup, disconnect the battery and loose the gradually learned compensation for the dirty throttle body and you'll have a bouncy idle and/or stall condition until either the PCM relearns the idle parameters or you clean the throttle body. (Trust us, cleaning the throttle body will save you from going insane!).
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #6 ·
update

Thanks all for the advice.

I cleaned the throttle body tonight. First time it had been done to my knowledge and the vehicle has 107,000 miles on it. I was caked with dirt and grime. Got it really clean, nice silver sheen to it, reconnected everything and I was simply amazed at how smooth the engine is now running.

Absolutely no rough idle at all, quieter idle actually, A/C running doesn't even phase the idle now. I expect it will help a gas mileage a little bit too?
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
Glad you're a happy trailvoy member. The mass of collective knowledge is such a relief to know it exists SOMEWHERE. (We can sometimes out diagnose the dealer, and if you're a DIY'er you can save THOUSANDS $$)

The throttle body issue is all because the evil trailvoy design team left off a $3 PCV valve, thinking the engine wouldn't need one. But then they failed to run a long-term test that would show that it did.
 
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top