Appropriate RPM for choke

[amg5872]

Hi, all. I just had some carb adjustment done by a local shop on my '73 E3 and now when I start the car when it's cold the engine revs up to 3000rpm. I immediately kick it down because I don't want the engine to rev so high when it's cold, but this makes me wonder: 1) what is the proper rpm for choke start; and 2) what is the proper way to use the choke -- do I kick it down after a minute, or just wait for it to warm up and go down itself? I recognize these are probably boring rookie questions, but thanks in advance for your guidance. BTW I did search the forum for answers before posting. Thanks.

AG

 

[Stevehose]

Fast idle speed should be 1900 +- 100 rpm.

Procedure before starting cold is to press pedal to floor once to engage cold start mechanism. Start engine, should idle at above rpm. Once warm a quick blip of pedal will bring it down to normal.

3000 rpm is way too high.

 

[HB Chris]

And you can blip it down sooner, as long as it continues to idle. We have all been told not to let car sit and idle, drive off slowly to let it warm up.

 

[EJ333]

To piggyback on this thread, once the engine is warmed up on my '71 coupe, how do I adjust idle down to around 1,000 ? It seems to like to stay at 1,500.

 

[amg5872]

Thanks guys, I appreciate the info.

 

[Beaudave]

Hi there!
Reading this 10 years old thread. Very interesting. And, I have a question: My coupe is a '75 injection with automatic choke, I believe, driven by a temperature probe. My car sleeps in my heated basement every night. So when I start it in the morning, it almost doesn't turn on the choke. Or just a little bit. As soon as I pull it out the engine revs up from about 1200 to 1600 rmp, or so. It usually takes me about 3 to 5 minutes to close the garage door, put on my jacket, shoes, or whatever is needed. Sometimes even a couple of minutes more to take the garbage out or whatever. So I was wondering: is that automatic choke absolutely necessary? because if the car engine starts fine, maybe it is useless to have the engine reving that high, while it could just sit there running at a lower rpm.
Another question: does it really help to press a little, or to the floor, the gas pedal before ignition? during ignition? Makes me realize that perhaps, when voltage is on, the fuel pump can pressurize a little amount of gas that would help the engine to start ? Because indeed, sometimes my engine starts, not at the first try, but at the second... Because I remember my old carb car that would start without pressing the gas pedal at all...
Thank you for your advice.

 

[bengal taiga]

Hi there!
Reading this 10 years old thread. Very interesting. And, I have a question: My coupe is a '75 injection with automatic choke, I believe, driven by a temperature probe. My car sleeps in my heated basement every night. So when I start it in the morning, it almost doesn't turn on the choke. Or just a little bit. As soon as I pull it out the engine revs up from about 1200 to 1600 rmp, or so. It usually takes me about 3 to 5 minutes to close the garage door, put on my jacket, shoes, or whatever is needed. Sometimes even a couple of minutes more to take the garbage out or whatever. So I was wondering: is that automatic choke absolutely necessary? because if the car engine starts fine, maybe it is useless to have the engine reving that high, while it could just sit there running at a lower rpm.
Another question: does it really help to press a little, or to the floor, the gas pedal before ignition? during ignition? Makes me realize that perhaps, when voltage is on, the fuel pump can pressurize a little amount of gas that would help the engine to start ? Because indeed, sometimes my engine starts, not at the first try, but at the second... Because I remember my old carb car that would start without pressing the gas pedal at all...

Something may be lost in translation.

Your post references “injection”. While all internal combustion fuel delivery systems share similarities, comparing carburetors with fuel injection is not unlike comparing cats with dogs. “IF” your car is fuel injection equipped, it is typically designed to include a cold start feature or system that serves the same function as a carburetor choke. If you operate your vehicle in a warm climate, a choke or cold start feature may not be necessary for normal operation. However, if or when you need to start your engine when ambient temperatures are cool or cold, the choke or cold start systems may be very welcome features.

BTW, just as a carburetor choke can be adjusted for fast idle speeds and disengagement, the same is true for most (if not all) original equipment fuel injection systems.

These resources may be helpful:
https://e9coupe.com/tech/dljet/dljet.pdf
https://e9coupe.com/tech/autobooks/autobooks_manual.pdf (Page 33, et. seq.)