Haunted S10

Last summer I bought a used 99 S10 4x4 with the 4.3 eng and 5sp trans. After a few weeks of driving to and from work I noticed that at a constant speed the eng would lag or stumble ever so slightly. This
happens every 30-45 seconds. The truck has been to 2 repair shops. #1 changed the fuel filter. #2 did complete tune-up, new plugs, clean injectors,etc, also new cat converter ($$$). Both mechanics road tested the rig and felt all was fixed. Well the problem is still there. I noticed that in the mornings when I have the defroster on this hesitation happens. When the defroster is off the truck runs as new. ??? I did notice that when I set for defrost the AC compressor cycles on-off every 30-45 seconds. What's up??? this is driving me NUTS!!! LOL Dave
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No, Dave you are not nuts.
The A/C compressor cycles when the defrost is on in an effort to extract excess moisture from the air to better keep the windshield from fogging up. To run the compressor dose take a decent amount of power (2-4hp? someone know out there know the exact number?). Also, if your compressor is beginning to die, it may be dragging a little too much.
Hope this helps!
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Dave,
Does it ever lag/stumble when the climate controls are set to off? If the answer is no, your A/C compressor is causing some serious drag and causing your lack of power. This can be caused by an overcharged A/C system, lack of oil in the A/C system, or just that the compressor is dying.
You should not feel any difference with the A/C on or off per way of power. While with some cars (mostly little 4-bangers) the A/C does suck up enough juice to cause a ntoiceable lack of oomph, the 4.3 is ballsy enough that you won't even notice. My wife drives a 98' Sonoma SLS, 4.3/Auto and you can't even tell when the A?C is on.
Doc

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On Mon, 19 Jan 2004 08:59:34 -0800 (PST), snipped-for-privacy@webtv.net (David Carl) wrote:

Also like to add that a cycling compressor can mean low refrigerant system pressure (not enough freon, as oppossed to too much). Either way, a good A/C shop can tell you right off if this pressure isn't right.
Re: Power and A/C.
I too have noticed that in recent vehicles (I myself am all the way up to 1989) power and fuel efficiency don't drop off when the A/C is on. But I also used to drive the full size GM V-8 sedans, and with those (carburated) cars you could always notice the A/C on: 81 Chev 305, 83 Olds 307 (especially the Olds), etc. I knew someone who had an Olds wagon 350 who wouldn't tow with the A/C on cause (he said) it robbed too much power. In those days A/C affected the power and the wallet. Today it doesn't make any difference on my 89 S-10 4.3 or my dad's 89 Towncar 5.0. I wonder if fuel injection and advanced computer control is making the difference these days, more so than just having a big engine.
Jeff
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With my 91 S-10 when the A/C is on, there is a slight but definitely noticeable power loss...May be wrong on this but doesn't the timing advance change a bit when the A/C is running?
Going up steeper hills, I'll sometimes will turn off the air off for a bit extra HP
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check your valve adjustment and compression test then get back to me
Dan
David Carl wrote:

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Valve adjustment and compression issues would cause a CONSTANT problem, not an intermittant one.
Doc

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Valve adjustment and compression issues would cause a CONSTANT problem, not an intermittant one.
Doc

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Thought I doubt it could hurt...
~KJ~
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No, it wouldn't hurt, but would be a HUGE waste of time. Ever try to pull a passenger side valve cover on a 99' 4.3 S-10? Not fun. Plus, the plugs are damned near impossible to get at without much effort and trillions of socket extensions and wobbles. Getting a compression adapter in there is even worse.
Doc
Doc

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Can't say I have. Haven't even tried to take them off of my 85 K5. Thanks yet again for more info!
~TLGM
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I have the exact same problem with mine 99 S10 4x4 automatic. Brought it to my mechanic who also has a Blazer 2003 (I think). He took it for a test drive and said it was the compressor that sucks out the power. I just got used to it and rarely notice it anymore.
Laurie

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