Only had this ZR2 for eight months so I'm not sure what is normal, but it sure seems like I lose a lot of power when the AC is on. I've owned 30+ different vehicles and none of them ever felt the power loss like this Blazer does.

160,000 miles, with what looks like the original compressor. All engine sensors replaced with AC Delco, including new fuel injector spider, distributor, MAF etc. Fresh top end engine rebuild......Runs excellent with good power until I turn on the AC, then it seems like a 20% power loss. Freeway driving it seems fine, its just the stop and go that really frustrates me. When accelerating from a stop it has a hesitation type "chugging" action until higher RPM's are reached, very unusual as this does not happen with the AC off. No codes.

Any input greatly appreciated.

 

best guess is when the ac is kicked on there is no compensation in the idle speed and the extra load is pulling the idle too low. old school vehicles had a elect selenoid on the throttle linkage that increased the idle, some newer vehicles still do.

 

I believe the Blazer's 4.3 is electronically controlled through the ECU. It does still have a distributor, but that distributor is also locked into place (you cannot turn it to adjust timing), all the timing is controlled by the engine computer, so the ignition, emissions, and fuel delivery is still all electronically controlled. Thus why there's not a crap-tone of vacuum hoses under the hood of the 98+ 4.3 equipped S series (can't say the same about the HVAC system, not sure why GM decided to leave all that vacuum controlled...)

My old Toyota with a 22re had a idle kick-up valve for both power steering and AC on that actually created a vacuum leak via a solenoid to bring the RPM's up :P everything was vacuum controlled under the hood of that truck... each manufacturer seems to have it's own ways of doing it through the years, but I'm sure it's all electronic now.




I would almost suspect a failing compressor... But if the compressor is getting to the point where it's dragging the motor down, it would be making a hell of a noise while it's engaged and cycling... Does the AC actually work good when it's running?

 

I would almost suspect a failing compressor... But if the compressor is getting to the point where it's dragging the motor down, it would be making a hell of a noise while it's engaged and cycling... Does the AC actually work good when it's running?


Ac is beautiful, nice and cold, no noises from compressor. Idle is perfect, nothing is out of place. Its just this dang sluggish, intermittent hesitation type thing till it gets up to a constant speed.

Reminds me of an old Mercedes I had once, where I almost had to turn the AC off when accelerating from a stop light just to get it to run properly.....this is not that bad but it feels like the engine is starving for air or fuel.

 

What is your idle out of gear no AC and again in gear with AC?

George

 

Idle never changes, always about 650 rpm or so. IAC valve is the only sensor I never replaced due to my idle in all conditions is perfect.

When I start from a stop with AC on and it hesitates/stutters and I switch the AC off, I get full smooth power. Crazy.

 

Sorry for a dead thread comment but has anyone ever found a fix for this? My 01 4dr 4wd is having exact same issues although it also does like a weird air sucking noise combined with staying in 1st gear WAY too long on takeoff. A/C off it runs like a swiss watch.

 

You likely have a vacuum leak in the control module. Does the idle suddenly increase when you turn on the AC? Do the short term fuel trim numbers jump?

George

 

Dropping the ol girl at the shop tonight and I'll have them check this exact thing. This forum rules!!

 

Hope they get you sorted.

George