ok so my chock plate light came on the other day or so im told its the chock plate light,for no reason and the car is running at a extremly high idle.when i p/n it idles between 700rpms to 1700rpms,when in gear it still only drops around 700-900 rpms.it wants to diesil alittle when you shut her off sometimes not often,but other then that she running twice as strong pulling really nice also its a little rough to start after it sits now to,sometime i have to hold pedel to floor to start.here is a pic of the light its the one with the two parelle lines and the symbole in the center at the top.
http://i75.photobucket.com/albums/i2...t/100_4112.jpg
shold i try to rebuild carb?motor was rebuilt 25,000 mile ago with rear end and tranny but the previous owner used original carb.any thought on what to do?also it a 85 berlinetta 305 lg4/700r4

 

Leave the carb alone. It it NOT the problem, strange as that may seem.

The light labelled "Choke" is actually the "Alternator" warning light. The connection us, the choke will never be fed electricity except when the alt is charging; and for whatever reason (emissions certification I'd guess), the factory lettered it that way.

Get a new aternator.

 

I've had several Alternator connectors go bad on me over the years,..... It's quite possible that the wires running to the plug are bad - or bad right at the plug. The 2 wire plug on the Alt could be the problem and the Choke heater relat could be causing the indicator light to malfunction.

But that is not the reason the car is idleing so high.

It's possible that the choke on that carb is original and defective and simply needs to be replaced. ( Check to see if it's held on the carb by rivets or screws. ) The Fast Idle screw ( pass side of carb ) could need adjustment and a vacuum leak could also be causing the engine to race. The rod to the lower carb butterflies could have a worn spot and not allowing them to close correctly or the driver side idle screw could be set to far. Just understand that there are MANY things that could cause the engine to act that way.


Here's a diagram or the Berlinetta CHOKE light wiring:

 

The car is idling high because the choke is on. It's doing what it's supposed to do.

The choke is on because it's cold out. It's doing what it's supposed to do.

The choke stays on until the electric heater has heated the stat in there up enough to make it come off. The power to the heater is fed to it via the choke relay, which in turn is operated by the alternator's diode trio circuit; it operates such that the relay opeartes when there is ignition voltage at one end of the coil (key on), but not at the other (alt output). When the key is on and the alt is working, the relay releases. Not very intuitive but quite functional.

The relay will remain in the "unhappy" state as long as the alt does not supply its coil with power.

Conclusion:

The reason the choke is staying on is because the alternator is not working.

See my signature for helpful troubleshooting advice.

While it's possible that something else could be bad, the highest probability item is the alternator. Start your troubleshooting there. Measure the voltage across the battery with the car running. If it's less then 13V, the alt is not working. In which case, replacing the alt, will fix both the high idle and the choke light. The alt is the simplest explanation that fits all the facts.

 

yeah im going to replace altenator first cause the voltage gauge is only at 8-10 volts when car is running.thanks for the help ill let you know if it fixes it or not.

 

Yeah, this thread belongs in the electronics dept.
Check the C/H fuse before replacing the alt. If it's bad the choke won't heat up & the alt. won't charge either.

 

My 86 Z28 is doing the same crap, I can't get the idle to remain the same. I'll tune it to near perfection one minute with the idle at 750 rpm and then the next minute the RPMs are way up to 2000 rpm and the next minute the idle drops so low it dies. I don't get the choke light on any more, but I do get a little buzzing like it wants to come on (made the same noise that it used to). I had bought a replacement carb and the performance just got worse. I've tried the mixture screws, I've checked the float, etc. The choke seems to open up okay.

Now I can't get my car to pass Maryland emissions inspections and I can only get about 100 miles to a tank of gas! I've got until 15 January to get it fixed or take it off the road.

I did notice that my voltmeter is reading low. Could this stupid alternator be the source of all my carb problems? I don't want to keep throwing money at this car and not get anywhere. I could see how a low voltage output from the alternator might skew the voltages put out to the M/C solenoid, etc. Please tell me that replacing my alternator may be my saving grace. I've been buried nose deep in my factory manual and my Rochester carb manual trying to figure out what the heck is wrong with this thing.

A local mech put a 70's Qjet on my car and got it running perfect. So, the low voltage thing does make sense.

 

MariahFan, in your case it seems to me your carb is just full of crap. Get it thoroughly cleaned out and rebuilt. The only other thing that can make the engine rev that much is a sticking fast idle cam, but it doesn't make it jump up & down, + it's easy to spot and remedy. Low voltage won't skew the mixture solenoid. The ECM would set the CEL for low voltage and the ignition would also crap out. But measuring actual voltages around with a digital multimeter is always useful.

 

listen to sofakingdom. whenever possible eliminate the known source of a known problem. you'll chase the wrong problem for sure otherwise. leaving a known problem could cause other parts to indicate problems falsely too.

 

fuse is good and altenator is dead.car is being put on hold i have a great trade offer on a 86 mazda b2000.truck has a 318 v8 out of a 89 ramcharger and looks and runs great so im going to trade then buy a camaro with a tpi setup instead. thanks for all the help and happy holidays