Changed Spark plugs, removed fuses for PCM for 2 hrs,still stalls out when A/C is on

[dwieg]

First of all let me say, I really truly appreciate this site and the other site that everyone used to use. It has helped me immensely over the years.

Here is the deal, I was getting a P0301 code and a pretty rough ride, so after looking up what the code was, I decided to change the sparkplugs on my 2005 Envoy XL SLT 4x4 with 135k miles on it. The plugs were still original. So I disconnected the neg battery cable, removed the resonator and commenced to changing the plugs with Bosch Double Platinum plugs. Took about an hour. Plugged up the battery again, started the engine and let it run a bit ~5 mins, turned it off, put the resonator back on, and drove the truck around for about 10 mins. I noticed that as I came to stop signs and the truck went to idle, if the A/C was on, the engine would stall out. Go down from around 800 rpm to less then 500 and then just die.

So I look on here to see what could be the cause, figured the PCM is trying to learn the new setup, so I figured I would drive it more. I drove in this morning for a 20 mile commute, at the end of the drive the engine still stalls out with the A/C on when at idle, but not with the A/C off. A/C off the idle is around 800 rpm.

So the question is do I need to go back and do the Throttle Body cleaning, and have the PCM relearn the newest setup with a clean system? Or is there something else that could be going on here?

 

[Sparky]

Yup I would start off with cleaning the throttle body. Disconnect the battery while doing so.

 

[Ilikemy3s]

First do that Sparky recommended and clean the Throttle body .. Also many people here also recommend putting in the AC Iridium plugs. Just my 2 cents

 

[Wooluf1952]

Welcome


In case you haven't heard:
http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/


And: http://gmtnation.com/f25/why-you-may-need-clean-4-2l-i6-throttle-body-799/

 

[xtitan1]

Welcome.

And I would have cleaned the throttle body first thing, brother! Rough idle and AC issues necessitate a throttle body cleaning before you try and troubleshoot it any further. We're not saying that's for sure the problem, but more often than not, it is with these trucks. Definitely do it, it's a quick job (well it's fast if you are having MAY do it alongside you lol).

I also have heard that these trucks don't like the Bosch's or anything but AC Delco iridium plugs, but that's entirely from word of mouth. However, I have no personal experience either way to back any of that up.

 

[dwieg]

Thanks so much to this board, just being lazy at first, but I should have done the TB initially as well.

I hadn't read too much about the Bosch plugs being bad for these, I guess I will just have to see how it goes along.

Now my next task will be to replace the fuel pump and sensor because mine has gone haywire.

 

[gmcman]

I would cut your losses with those Bosch plugs and install the AC 41-103 iridium plugs. The double platinum plugs IMO don't belong and one reason I am told is when you seat the plugs, the electrode is in a fixed position for every cylinder, but with those Bosch plugs, you have an electrode 180 deg from where the factory location is, those plugs can fire off either ground electrode and it is random. May or may not cause an issue but why chance it. Also factor in the resistance in the plugs, another thing to chance with these coil packs and if you fry them it can be an expensive swap for 6 coil packs.

I remember a co-worker installed the platinum-4 plugs in his corolla and it wouldn't run worth a crap, back to the OE plugs and it purred.

Here's the re-learn, pull fuse 10 instead of the battery, if the TB still acts wonky then disconnect the battery. Reason is some people end up with HVAC actuator issues after disconnecting the battery.

http://gmtnation.com/f93/throttle-body-trailblazer-throttle-body-relearn-4-2-a-8363/

 

[dannyoaks]

As I've learned with the 4.2 throttlebody cleaning is always the first step, the 103 iridium plugs are great in smoothing out any rough idle, I recently did both repairs at the same time for no other reason than I hit 100k miles. The tb had a slight gunk on it, nothing like the day I bought it, so so filthy, and the plugs looked their age except the #3 plug, which had corrosion that ate up the hex on the outside and was severely gunked up on the electrode end. My figuring on that was the dealer where I bought mine probably used a pressure washer to clean the motor and water got trapped under the boot. That was 6 months after I bought it, now it's been 2 months since the plug change and she's purring like a kid and grocery hauling kitten.