2003 Trailblazer A/C issues

[sntrym95]

Hey all,

Normally I'm posting over in the 88-98 side, but my wife just bought an 03 Trailblazer (4.2L I6, 4x4, EXT), and I'm having some A/C issues. But first, some background...

The water pump went a few weekends ago, and the engine just barely overheated. I replaced the pump, and filled the coolant accordingly, all was well with that.

The problem is that the A/C compressor will kick on momentarily and then kick back off. When it does this, the engine either almost stalls or stalls. I checked the hi/low A/C pressures, and they register at 220/40 respectively. I also jumped the low pressure switch on the condenser, and the compressor still behaves the same way.

So, right after I replaced the water pump, the SES light came on, and the coolant temp sensor was throwing a code, as well as the MAP sensor. I cleared the codes just in case, and drove it. The SES light returned soon, and again the coolant temp sensor registered. I bought a new one, but instead of replacing it, I disconnected the harness for the existing one and monitored the engine. The check gauges light came on and the temp did not register on the gauge. I plugged it back in, and all was well, as expected. So I took the new one back and bought a MAP sensor thinking that would cure the stalling issue. It has helped, as it doesn't stall now, but the A/C compressor kicks on then right back off still.

Any help is much appreciated.

Thanks!
Mike

[sntrym95]

I should add that when I disconnect the MAP sensor, the A/C works perfectly fine, but the engine goes into Reduced Power Mode.

[clinebarger]

What are the code numbers?
Check the wiring to the Ambient Air Temperature Sensor (behind grille).

If this happened right after the water pump replacment....I bet you have a wiring problem or something unhooked, I know what PITA these are to put pumps on.

[sntrym95]

I don't have the code numbers any more, unfortunately. It seemed to work fine yesterday though when not in idle. When in idle, it's not working still. I'll try to pull the fan shroud/fan back off this weekend and see if something isn't right in there.

Thanks!
Mike

[clinebarger]

I was thinking about your problem......Im guessing you unhooked the battery?

That resets alot of "learned paramerters", Try cleaning the Throttle Body bore. This can raise the idle & cure the "stalling" & A/C issue.

[sntrym95]

Yep, disconnected the battery a few times to clear codes. I haven't checked the bore yet, but I've only ever see that cause problems across the board with carbon build up. The problem is still happening, but only in idle now. Since she drives it on the freeway most of the time, it's not a huge issue for now. I'll probably take another look this weekend.

Mike

[spudz]

I work at a chevy dealership and work on these all day long.... What happened is... when you did your water pump, you prolly disconected the battery and it releared its factory idle.. 100 bux says your throttle body is coked up with carbon. Get some carb or top engine cleaner and clean the throttle body real good. That should fix the almost stalling and a/c problems... SECOND. I bet the code your getting is a p0128???? if this is so.... stick a thermostat in it..TRUST ME.... we get one in a week with the same problems your are having.. OHH and there is a elbow vacuum line that connects to your plastic air intake, BE sure to hook it back up or you will set a lean code.. Its easy to miss.

[68C15]

^^^^^^
I'll back spudz up on this. seen it myself plenty of times.

[richards72chevy]

So did you solve the problem?My mom has an 04 trailblazer with the same problem.