05 Trailblazer acting weird - stalling, sluggish, weird gauges, etc - PCM?

Blaze

Blaze

The Jeeper Reaper
Joined
Aug 9, 2005
Location
Wake Forest, NC
So trying to figure out WTF is wrong with my wife's 05 Trailblazer with the I6 in it. It has 215k miles on it now, we've owned it since it was almost new. I have maintained this thing very well, but it is getting a little long in the tooth and we are trying to figure out what our plan of action is here.

Oil is fresh, transmission only has about 40k miles on a rebuild, tune up is only about 50-60k miles old, new coil packs recently, etc.

For the last year or so the thing would randomly stall. Mostly after driving it for a while and after starting. Occasionally when sitting at a light it would die, but this was extremely rare and only did that a couple of times. Most of the time it was after a short trip. Like my wife would leave work and stop at my son's preschool to pick him up, and when she would get in it it would start and stall, then be hard to get going and then smell like gas once it got going. Seems like something was flooding the engine.

We took it up to the mountains last weekend, it did fine until right at the end when we were going up 421 towards the BRP and by the time we got to the top of the mountain the temp gauge was reading a little hot (not bad, it normally sits parked at 210, was sitting maybe around 225 at most, but it never EVER goes over 210 so it was a little weird. The cabin we were staying at had a steep driveway and the thing would BARELY make it up. It wasn't really like the trans was slipping, it was just kind of like it couldn't get the oomph to get up. Like maybe even the torque converter wasn't doing it's thing. It was weird. The next morning it was back to normal but didn't quite feel right, and the temp gauge was going crazy. It would sit at 210 like normal and then randomly drop down to 175 and occasionally it would go down at sit at 120ish. Then jump back to 210. It was bizarre. The ammeter sits right where it should, but for the last 6 months or so the oil pressure gauge has sat at around 110psi. :lol:

We got home fine, and it only did the stalling thing once when we got back to Raleigh.

I'm wondering if it is a PCM issue, the weird electrical stuff, the weird shifting, the stalling, etc. I have checked wiring and grounds and no problem at all. Does anyone have any ideas?
 
But would it drop it that low? I mean, it sat at about 125 for a while, and we had been driving on the highway for a good hour at that point.

I won't rule out the fuel pump, I know the sender has been dead for the last 100k miles. I've had two senders put in under warranty, not sure if they replaced the pumps at the same time or not.
 
i wouldn't count on the gauge for anything, with all of the cluster issues gm had. there is no way for the temp to go from 220 to 125 within a few min. the temp is 125 after running for a min or so, there is no way it was 125 under operating conditions.
 
These engines are notorious for the VVT solenoid to give problems and actuate or bleed pressure off while driving. Could be your stalling problem there. Its available thru DORMAN for relatively cheap and is right behind the power steering pump. I have changed a half dozen or so the past year for idle and stalling problems might at least have it scanned to see if it is the culprit or working properly.
 
transman731 said:
i wouldn't count on the gauge for anything, with all of the cluster issues gm had. there is no way for the temp to go from 220 to 125 within a few min. the temp is 125 after running for a min or so, there is no way it was 125 under operating conditions.
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Exactly, during the summer the thing starts at 125 sometimes. :lol:

bannerp said:
These engines are notorious for the VVT solenoid to give problems and actuate or bleed pressure off while driving. Could be your stalling problem there. Its available thru DORMAN for relatively cheap and is right behind the power steering pump. I have changed a half dozen or so the past year for idle and stalling problems might at least have it scanned to see if it is the culprit or working properly.
Click to expand...

I just read online about that and some of the symptoms really do sound like that. My wife said the SES light came on today so I'll scan it tomorrow and see what comes up.
 
Knock on wood....my mom hasn't had any problems with her 06 Envoy other than the rear hood/cowl seal issue. I got the updated one, dried the water out of the spark plug holes, put in new plugs and new boots with a crap load of dielectric grease and it was back to new again. If you haven't done that yet, I'd suggest it. The front three spark plug holes were full of water where it was running down the "valley" in the valve cover when it rained.

I was also surprised how ballsy that 4.2 I6 is and at how well they stop. I'm going to tweak the tune a little and see if I can get better than 17mpg out of it though.
 
So just a quick update. I replaced the VVT sensor and the truck seems to run a lot better on the highway, but it is still having the stalling problem.

My wife called me this morning and she went in to drop off my son at school and when she came back out it wouldn't start. Well, it would start, but wouldn't really run. It started but the idle was extremely low and she said it was almost like the truck didn't know it was running because the tach was at zero and she she pressed the gas pedal down it didn't do anything at all. She turns it off and on a few times and it did this every time. She called me and let it sit for a few minutes while I talked to her about it and then it started up, but was a little rough at first till it worked itself out.

I scanned the codes, nothing at all. I am perplexed.
 
I've spent the past few weeks working on an 03. Here are a few things I've learned that may be helpful in your diagnostic activities:

The fan is capable of over-cooling the engine if it defaults to full speed (to my surprise)

There is a TSB around that links fan overspeed to perceived transmission shifting issues

The thing throws tons of codes, the fact you have none is definitely a clue of something.
 
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