This has been immensely helpful, just finished rebuilding mine on a 87 camaro. So bringing the screw out(left) opens the choke. Tightening it would then increase the cs idle
The cold Idle screw, is for setting the cold engine speed. It has noting to do, with trying . To put more tension on the carburetor choke fast idle cam. That lever and cam are there, Because when a Engine is cold . It needs to have the carburetor throttle blades opened more . So more air and fuel mixture. will go into the engine. And when you first start,the cold engine. You are suppose to step down on the Accelerator pedal. once or twice. Than take your foot off the Accelerator pedal. And that lets the choke system,to be able ,do its job. And part of that is it helps the engine idle faster.Now ,when the cold engine is running for a few seconds. Maybe about 6 to 10 seconds. You step on the Throttle again. And that lets that lever move away from the cam,with the steps on it. And the cam will drop down a little. The lever is resting on the next step down on the cam. And that lets the cold engine speed slow down some. Now the movement of the Choke system,Is controlled by that round black housing. That has a round coiled up spring inside. That is called a Bimetal spring. That is effected by air temperature. Now that,s where you adjust how long the carburetor choke stays on. And a coarse, that will put more tension on that lever ,against the cam. If you loosen the screws, that hold the choke housing spring. And turn it to the left . That will make that spring in the choke housing, put more tension on the choke system levers and cam .And will keep the choke system on longer.And more tension on what you are pointing to.
thanks that was really helpful the high idle cam on my 85 Grand Marquis 351W isn't working (I think) as the high idle never stays on and the car floods out and dies between that comment and this video maybe I can fix it... I'm broke and in high school so if I can't I'll end up scrapping the car
HI. I would have explained it a bit differently. The adjustment really has nothing to do with "Tension" It's just an "adjustment". The spring is there to prevent the adjustment from moving on it's own. Great video. Keep up the good work.
Recently had to mess around with the choke on my carb and that fixed a few things but it seemed like it wouldn't get off of high idle, had to take press down on the linkage and it felt like it would "step down" each time it went down a "step" it seemed to move the throttle cable hoping since i had to adjust some things on the choke that this just needs adjustment because of the other changes made, thanks.
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Hello Joe......I have a Rochester Quadrajet 7029263 being used on my '69 GTO Ram Air IV which isn't really the exact replacement for the Ram Air IV engine but the correct Quadrajets are very hard to find-- 7028273 and 7029273. I looked at my fast idle set screw and the spring is located on the back side or the CAM side. My fast idle doesn't set when engine is cold and may be due to some debris I found on the spring of the fast idle set screw. I recently changed the choke pull-off diaphram and cleaned up the divorced oven coil and cleaned up the linkage the best I could with Gumout Carb Spray. I could send you a photo of the debris I have on the spring......?
Hi. Great informative video. Thou I have a question. I have a D GAS 38 twin weber carb on my Ford Capri 3.0 Automatic. After adjusting my fast idle screw to decrease the high idle rpm from 1800 to 1200 rpm My V6 Essex engine has now developed an intermittent misfire. The car runs and accelerates fine, but for the first 10 mins of the journey it seems to misfire which it wasn't doing before. any idea's please ? Regards Nick
That screw has noting to do about tension. That screw and spring is used to set the cold high speed RPM,s What the car manufacture of the car whats the Engine RPM,s to be at . When you start the cold Engine up.And the spring is there to make sure the screw can not . Turn in or out by itself. You turn the Screw in and the cold Engine RPM,s will be higher. Turn the Screw out and the RPM,s go down .You look in Automobile book for that car, for the specifications.
I always seem to have a higher than normal idle on my Q-jet. Even when the choke is off. I've turned the idle screw so it doesn't even touch the idle stop. Still higher than normal. Could be the high idle setting is too tight? I'll give this a try. Thanks!
What did you find out? It could also be a sticking throttle cable, I had that once and my car would accelerate by itself and diesel when I'd shut it off. Could also be a vacuum leak.
Joe I am stuck. My Rochester four barrel has no Fast Idle on the cold start and my cars engine cuts off when I try to take off. I am hoping when I get home all I need to do is crank this adjustment in.
I have heard 3 . But this guy says 4 i do believe...but i think the thing is the start up choke takes the driver's side choke adjust screw off it's adjust seat by about the thickness of a nickel edge. Then when the passenger side is properly adjusted for choke startup it will step down such that then the driver side idle set screw is seated on it's adjust point so you can then adjust the driver side true idle.
This is very helpful. I am having g a problem with mine not going onto fast idle when cold on my 88 cutlass supreme classic. I have to manually close the choke with my finger with the fast idle cam lever and the car runs great at that point and will kick off of fast idle no problems. But in the morning the choke stays open even after I try to set it with the accelerator. I can not figure this out, any input on where to look?
@@joebridger1346 yep mine ended up being the air cleaner spacer catching the choke arm not allowing the choke to set. I shaved down a spot for the arm to move freely and never had an issue since.
@@joelbravick9545 that's not it.....shoot......it will start first thing in the morning but won't run.... then it just cranks and I have to give it a shot of starting fluid to get it going....any ideas...the choke and high idle are working fine
@@joebridger1346 how is your fuel pump? You might need to adjust the carburetor if your fuel pump is alright. When I got my reman the car wouldn't run at all and being new to carburetors I didn't know what was going on. I read some forums and they all said a good starting point was the 2 screws at the base to be turned all the way in and then back them out about 2.5 to 3 turns and that helped and I ran it that way for a little bit.
@@joebridger1346*Do you have a secondary vacuum break (rear)? When the diaphragm starts leaking in the rear vacuum break, it doesn't pull the choke lever back enough for the choke to clear and reset when cold*
by pressing the gas pedal when the engine is off and cold. this allows the choke blade to close, idle cam to rotate back and this sets the throttle blade to the highest of the 3 idle cam steps. (plus the accelerator pumps sprays a shot of fuel into the primaries)
At 2:05 the cam is considered to be on the highest step correct? I'm reading the settings for the M4MC and it's telling me for fast idle cam adjustment set to the following when on the car: 1600N H/S. Am I correct to understand that 1600 is the desired idle when the choke is on, N stands for Neutral in my application as it's a 4-speed, and most importantly the H/S...possibly stands for High Step on the cam follower?
Texas - Yes that is correct. I changed our the Carter carb on my jeep to a Motorcraft and I couldn't get my choke to work properly. After 6 months I finally read the carb instructions and it says to push the gas pedal down and release before starting. Instantly my choke worked properly. One question though - I could use a little higher idle speed when cold. Does screwing in this adjustment screw increase cold idle?
@@markshort6049 should be, as the screw opens/closes the throttle blade (only fast idle setting). I think normal curb idle speed (throttle opening) is controlled by a separate idle stop screw on the driver side front of the carb
This has been immensely helpful, just finished rebuilding mine on a 87 camaro. So bringing the screw out(left) opens the choke. Tightening it would then increase the cs idle
Absolutely great advise to get my Corvette idle down after warm-up. Thanks for the video - its all makes so much more sense now.....
That's exactly what I needed. Quick & to the point. Best explanation i could find! Good job! Thanks!👍
this is the most helpful and truly informative thing ive ever seen on utube thank you very much
Fine video about the fast idle cam on the Quadrajet. Thanks
The shroud of mystery is lifted from this esoteric part of the Quadrajet. Even the factory service manual is vague.
Thank you for sharing, you made this easy to understand.
Best video yet
answered my question on my Rochester Carb. thanks
The cold Idle screw, is for setting the cold engine speed. It has noting to do, with trying . To put more tension on the carburetor choke fast idle cam. That lever and cam are there, Because when a Engine is cold . It needs to have the carburetor throttle blades opened more . So more air and fuel mixture. will go into the engine. And when you first start,the cold engine. You are suppose to step down on the Accelerator pedal. once or twice. Than take your foot off the Accelerator pedal. And that lets the choke system,to be able ,do its job. And part of that is it helps the engine idle faster.Now ,when the cold engine is running for a few seconds. Maybe about 6 to 10 seconds. You step on the Throttle again. And that lets that lever move away from the cam,with the steps on it. And the cam will drop down a little. The lever is resting on the next step down on the cam. And that lets the cold engine speed slow down some. Now the movement of the Choke system,Is controlled by that round black housing. That has a round coiled up spring inside. That is called a Bimetal spring. That is effected by air temperature. Now that,s where you adjust how long the carburetor choke stays on. And a coarse, that will put more tension on that lever ,against the cam. If you loosen the screws, that hold the choke housing spring. And turn it to the left . That will make that spring in the choke housing, put more tension on the choke system levers and cam .And will keep the choke system on longer.And more tension on what you are pointing to.
thanks that was really helpful the high idle cam on my 85 Grand Marquis 351W isn't working (I think) as the high idle never stays on and the car floods out and dies between that comment and this video maybe I can fix it... I'm broke and in high school so if I can't I'll end up scrapping the car
HI. I would have explained it a bit differently. The adjustment really has nothing to do with "Tension" It's just an "adjustment". The spring is there to prevent the adjustment from moving on it's own. Great video. Keep up the good work.
Thank you. This helps me
Recently had to mess around with the choke on my carb and that fixed a few things but it seemed like it wouldn't get off of high idle, had to take press down on the linkage and it felt like it would "step down" each time it went down a "step" it seemed to move the throttle cable hoping since i had to adjust some things on the choke that this just needs adjustment because of the other changes made, thanks.
thanks. that was very helpful
Very well explained!!!
thanks mr. Rogers
Good video!
Good explanation
Thanks for making this video. I have a 72 cadillac hearse. And I don't like how high it runs cold.
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For 2bbl Ford, I adjust it when hot. Go in till it touches and back off.
Good vid.. Yes very helpful..
So does it return to the first step when tje engine is cold?
Great video, keep them coming. My 81 turbo seems to rev up too much on a cold start. Will adjusting the screw help?
should help, as turning the screw closes/opens the throttle blade
Thanx 4 the tip an Demo.
Hello Joe......I have a Rochester Quadrajet 7029263 being used on my '69 GTO Ram Air IV which isn't really the exact replacement for the Ram Air IV engine but the correct Quadrajets are very hard to find-- 7028273 and 7029273. I looked at my fast idle set screw and the spring is located on the back side or the CAM side. My fast idle doesn't set when engine is cold and may be due to some debris I found on the spring of the fast idle set screw. I recently changed the choke pull-off diaphram and cleaned up the divorced oven coil and cleaned up the linkage the best I could with Gumout Carb Spray. I could send you a photo of the debris I have on the spring......?
THANK YOU very difficult to see this with the choke installed...
Hi. Great informative video. Thou I have a question. I have a D GAS 38 twin weber carb on my Ford Capri 3.0 Automatic. After adjusting my fast idle screw to decrease the high idle rpm from 1800 to 1200 rpm My V6 Essex engine has now developed an intermittent misfire. The car runs and accelerates fine, but for the first 10 mins of the journey it seems to misfire which it wasn't doing before. any idea's please ? Regards Nick
That screw has noting to do about tension. That screw and spring is used to set the cold high speed RPM,s What the car manufacture of the car whats the Engine RPM,s to be at . When you start the cold Engine up.And the spring is there to make sure the screw can not . Turn in or out by itself. You turn the Screw in and the cold Engine RPM,s will be higher. Turn the Screw out and the RPM,s go down .You look in Automobile book for that car, for the specifications.
There's still tension being hard against the cam or backing off enough for it to move.
I always seem to have a higher than normal idle on my Q-jet. Even when the choke is off. I've turned the idle screw so it doesn't even touch the idle stop. Still higher than normal. Could be the high idle setting is too tight? I'll give this a try. Thanks!
What did you find out?
It could also be a sticking throttle cable, I had that once and my car would accelerate by itself and diesel when I'd shut it off.
Could also be a vacuum leak.
Joe I am stuck. My Rochester four barrel has no Fast Idle on the cold start and my cars engine cuts off when I try to take off. I am hoping when I get home all I need to do is crank this adjustment in.
i have a mercruiser 3.7lx with the same carb but mine dont have a high speed idle screw there
Great video! So, if I turn the screw all the way in first, how many turns should I go out (counter clockwise) just as a starting point? Thanks!
I have heard 3 . But this guy says 4 i do believe...but i think the thing is the start up choke takes the driver's side choke adjust screw off it's adjust seat by about the thickness of a nickel edge. Then when the passenger side is properly adjusted for choke startup it will step down such that then the driver side idle set screw is seated on it's adjust point so you can then adjust the driver side true idle.
@@pauldow1648 Very interesting. Thank for the tip...
Hey what happened if I backed my screw all the way out. ??? Is that a bad thing or a good thing ??? I need help now the choke won’t work!!!!
Thank you so much! I’ve been cussing for an hour
My Clymer book calls it a throttle stop screw.
👍Thanks!
This is very helpful. I am having g a problem with mine not going onto fast idle when cold on my 88 cutlass supreme classic. I have to manually close the choke with my finger with the fast idle cam lever and the car runs great at that point and will kick off of fast idle no problems. But in the morning the choke stays open even after I try to set it with the accelerator. I can not figure this out, any input on where to look?
Mine is doing this...did you figure it out
@@joebridger1346 yep mine ended up being the air cleaner spacer catching the choke arm not allowing the choke to set. I shaved down a spot for the arm to move freely and never had an issue since.
@@joelbravick9545 that's not it.....shoot......it will start first thing in the morning but won't run.... then it just cranks and I have to give it a shot of starting fluid to get it going....any ideas...the choke and high idle are working fine
@@joebridger1346 how is your fuel pump? You might need to adjust the carburetor if your fuel pump is alright. When I got my reman the car wouldn't run at all and being new to carburetors I didn't know what was going on. I read some forums and they all said a good starting point was the 2 screws at the base to be turned all the way in and then back them out about 2.5 to 3 turns and that helped and I ran it that way for a little bit.
@@joebridger1346*Do you have a secondary vacuum break (rear)? When the diaphragm starts leaking in the rear vacuum break, it doesn't pull the choke lever back enough for the choke to clear and reset when cold*
How does the cam return to high idle when the engine goes cold?
by pressing the gas pedal when the engine is off and cold. this allows the choke blade to close, idle cam to rotate back and this sets the throttle blade to the highest of the 3 idle cam steps. (plus the accelerator pumps sprays a shot of fuel into the primaries)
wow thank you sir my car is idleling at 1300rpm even wen hot and with the idle scew all the way out son i think that must be my problem.
Was this your problem?
At 2:05 the cam is considered to be on the highest step correct? I'm reading the settings for the M4MC and it's telling me for fast idle cam adjustment set to the following when on the car: 1600N H/S. Am I correct to understand that 1600 is the desired idle when the choke is on, N stands for Neutral in my application as it's a 4-speed, and most importantly the H/S...possibly stands for High Step on the cam follower?
highest step is the one you see (most to the left), as you described.
@@frederikkson156 Thanks I eventually got it. New problem, why do I get hesitation when blipping the throttle lol?
Gewiz is this a holly or carter?
carter baby!
That idle cam prevents my choke to come on .....
VFS Videos push the gas pedal down before starting
Texas - Yes that is correct. I changed our the Carter carb on my jeep to a Motorcraft and I couldn't get my choke to work properly. After 6 months I finally read the carb instructions and it says to push the gas pedal down and release before starting. Instantly my choke worked properly. One question though - I could use a little higher idle speed when cold. Does screwing in this adjustment screw increase cold idle?
@@markshort6049 should be, as the screw opens/closes the throttle blade (only fast idle setting). I think normal curb idle speed (throttle opening) is controlled by a separate idle stop screw on the driver side front of the carb
DANG that's a dirty carb.