Stop Idle Soleniod—rough idle?

[DWCaprice2017]

Hi, all!
This is Daniel, ‘84 Caprice, 305, electronic q-jet, w/ac:
While looking around the carb, I saw that the Stop Idle Solenoid shaft wasn’t touching the low/curb idle plate—I made sure that the linkage was set in the low idle mode. The shaft felt like it was sticking—pulling and pushing it was difficult. Also, there’s a rip in the shaft boot, I’m sure that’s not good! From what I’m reading, this could cause a rough idle…sometimes, I think just by looking at the engine the wrong way could cause a rough idle!

 

[69hurstolds]

If idle speed was already set properly via the curb idle stop screw, then it shouldn't be involved unless the a/c compressor is in use. Some cars (I don't know which ones, but I know later Chevys used it) also use the ECM via a solenoid to energize the solenoid under certain deceleration events. The rubber boot is just to keep dirt, water, and junk out of the solenoid. Which could lead to the exact condition you're experiencing. Rough movement or stuck plunger is not good. Setting the idle when the a/c compressor is on is accomplished when the solenoid plunger extends and gives it a tad more throttle, you take a wrench (7/16" I think?) and turn it in or out to adjust the loaded a/c compressor idle speed. Then, when the compressor is off, the solenoid disengages. Then the idle speed screw on the body of the carb takes over it's normal duties.

Check the operation by turning ignition key on and placing the HVAC controls to either Max, Normal or Defrost. It should send 12V to the solenoid and see if it energizes. If it doesn't, check to see if it's getting 12V by checking the 12V input on the wire going to the solenoid with a voltmeter. If it's not getting a 12V signal, you need to investigate the circuit at that point as to why.

If you need a new solenoid, you could try GM p/n 17068272. If you can find one.

ES85 or ES110 from Standard Motor Products is your best bet for a new one. It isn't GM, but it should work. GM ones are hard to find, and when you do, they're usually 100 bucks or more.

ES85

SMP ES85 NEW dle Stop Solenoid | eBay

PONTIAC 1978-1987. GMC 1977-1989.

www.ebay.com

ES110
Rockauto.com has it for $62.99. With the 5% rockauto discount code, you could get it shipped to you for around $70. Or search for a good used one somewhere.

More Information for STANDARD MOTOR PRODUCTS ES110

 

[DWCaprice2017]

If idle speed was already set properly via the curb idle stop screw, then it shouldn't be involved unless the a/c compressor is in use. Some cars (I don't know which ones, but I know later Chevys used it) also use the ECM via a solenoid to energize the solenoid under certain deceleration events. The rubber boot is just to keep dirt, water, and junk out of the solenoid. Which could lead to the exact condition you're experiencing. Rough movement or stuck plunger is not good. Setting the idle when the a/c compressor is on is accomplished when the solenoid plunger extends and gives it a tad more throttle, you take a wrench (7/16" I think?) and turn it in or out to adjust the loaded a/c compressor idle speed. Then, when the compressor is off, the solenoid disengages. Then the idle speed screw on the body of the carb takes over it's normal duties.

Check the operation by turning ignition key on and placing the HVAC controls to either Max, Normal or Defrost. It should send 12V to the solenoid and see if it energizes. If it doesn't, check to see if it's getting 12V by checking the 12V input on the wire going to the solenoid with a voltmeter. If it's not getting a 12V signal, you need to investigate the circuit at that point as to why.

If you need a new solenoid, you could try GM p/n 17068272. If you can find one.

ES85 or ES110 from Standard Motor Products is your best bet for a new one. It isn't GM, but it should work. GM ones are hard to find, and when you do, they're usually 100 bucks or more.

ES85

SMP ES85 NEW dle Stop Solenoid | eBay

PONTIAC 1978-1987. GMC 1977-1989.

www.ebay.com

ES110
Rockauto.com has it for $62.99. With the 5% rockauto discount code, you could get it shipped to you for around $70. Or search for a good used one somewhere.

More Information for STANDARD MOTOR PRODUCTS ES110

View attachment 249848

Thank you for the information!
Here’s the thing about the A/C, when I got the car nearly five years ago, the a/c system wasn’t working—no compressor, no fan blower, nothing turned on when the lever was moved. It’s been one of my lesser to-do projects on the car.

 

[Clone TIE Pilot]

Rough idle can be caused by 1,000 different issues on any engine. You need a dwell meter or a obd1 scanner to find out what is going on.

I had a rough idle that took me awhile to fix. Here are the issues I found that affected idle: leaking exhaust manifolds, leaking intake manifold gaskets, leaking brake booster, rusted out valve cover, incorrect PCV valve, thicker airhorn gasket that threw off A/F mix solenoid travel, incorrect fuel pressure, bad valve stem oil seals, and oil fouled sparkplugs.