Jimmy has hiccups

Trebissky

Active Member
Joined
May 16, 2005
Location
Durham, NC
Hi, I've got a question I HOPE you guys will find easy to answer. I have a 1990 GMC Jimmy that I bought as-is. It seems to run okay, except that when I have the AC on it tends to chug and hiccup when I stop at lights, and a few times it's even stalled. I can start it right back up, and once I get moving again it's fine... until I stop again. How can I get it to keep running smoothly when I stop with the AC on?
 
That's what I was hoping it is. Right now the idle is @ 700 rpm or so. Here's the NEXT question: how do I adjust the idle?

Did I mention that I've done almost NO automotive work myself, and what I have done was mostly on exhaust pipes? :lol: I'm definitely willing to learn, though.
 
Probably not the idle. It may be the A/C compressor locking up. when idling, have someone turn on the A/C and watch the compressor to see if it stops occasionally.
 
There's a part that's on the drive belt, only active when the AC's turned on, and this thing has a piece that pops out, then back in, every few seconds. You can hear it clicking in, then out, even with the hood down. Is that what you're talking about? I thought the compressor was the big silver canister-looking thing set farther back along the fender. :confused:
 
Trebissky said:
There's a part that's on the drive belt, only active when the AC's turned on, and this thing has a piece that pops out, then back in, every few seconds. You can hear it clicking in, then out, even with the hood down. Is that what you're talking about? I thought the compressor was the big silver canister-looking thing set farther back along the fender. :confused:
Click to expand...


There's a part that's on the drive belt, only active when the AC's turned on, and this thing has a piece that pops out, then back in, every few seconds. You can hear it clicking in, then out, even with the hood down.

That's the Compressor


The popping in and out is the Compressor clutch. When it's out, the compressor is off, when it's in the compressor is on and turning. The clutch is actuated by a electric magnet. I would say if it is cycling on and off it is either low of coolant, or it may have another problem such as a bad evaporator. The "hiccuping" is thecycling on and off. It take Horsepower to turn the AC Compressor, so going on and off it will give this affect. As it is going off and on the Computor is trying to adjust to the changing of the power levels to keep it at constant RPM's.
You mentioned it running 700 rpm's at idle, is this with AC on or off? Is the AC cold? as in what degree at the vents?

All this info will help diagnos your problem.
 
I would do a complete tune-up on it first. Get all the basics right and the problem might dissappear.
-plugs
-plugwires
-filters-oil and air
If any of these where bad....they could run fine at speed, but the added stress of the a/c could cause problem at low rpms-ilde.


Matt-my 2 lincolns :huggy:
 
If your comp ends up being bad check out car-part.com. I bought a comp for my Toyota for $35.00. Just put your info in and search all over the united states. I forgot to mention that's with shipping.
 
The popping in and out is the Compressor clutch. When it's out, the compressor is off, when it's in the compressor is on and turning. The clutch is actuated by a electric magnet. I would say if it is cycling on and off it is either low of coolant, or it may have another problem such as a bad evaporator. The "hiccuping" is thecycling on and off. It take Horsepower to turn the AC Compressor, so going on and off it will give this affect. As it is going off and on the Computor is trying to adjust to the changing of the power levels to keep it at constant RPM's.
You mentioned it running 700 rpm's at idle, is this with AC on or off? Is the AC cold? as in what degree at the vents?

-------------------------------------------------

The AC actually isn't very cold, let me see if I can get it charged up. Thanks for all the tips, I'll let you know. I still might want to increase that idle rpm, how do I do that? I gather there's an adjuster somewhere on the carburetor. It has one of those digital readout panels instead of regular gauges, looks to be around 700 rpm with AC on, might be about 800 with it off. I'd like to get it up to 800 with the AC running and see if that doesn't help.
 
Trebissky said:
The AC actually isn't very cold, let me see if I can get it charged up.
Click to expand...

Good luck, you've more than likely got R-12 in there. However, i just "converted" Nicole's '89 Celica last night with this "conversion in a can".. It's supposed to be some kind of oil that allows R-134a to work in a R-12 system. Her leak was coming from the low pressure service port, and fortunately, the conversion kit comes with a new valve for the 134a fittings, so I killed 2 birds with one stone!

You'll need this kit ($20), a fill kit for 134a ($20-$100), and a can or 2 of 134a ($10 each).

I got the 134a with the UV dye in it, so if it does leak out again, we can find the leak.

All-in-all, a neat little kit, from AutoZone. Can't tell ya the long-term durability of it, but it's blowing cold for now, and with the temps and humidity, she's happy now.

But, do it ASAP! Running your compressor low on refrigerant (and thereby, oil, too!) is deadly to it. This includes "defrost" mode.
 
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