My Fast Idle Ain't Fast!

[1964Comet404]

Good Day All! I hope you're Enjoying pleasant moments a plenty. I have a 1964 Mercury Comet 404, 4 dr. Sedan, L6/200/3.3L, Auto., Autolite 1100 Single Barrel Carb... I just replaced the Carb with a nice rebuilt one. I have Zero experience with this and have been reading the Shop Manual about the adjustments, but it just doesn't work for me. There are 3 Screws and a little plastic nut-like thing, which seems to limit the travel of the choke plate, and then of course there's the automatic choke which I don't know if it's set properly either. I turn it either way and I'm not sure what I'm doing, but it doesn't seem to make a difference. There are arrows on it and the word Lean going counter clockwise.

The carb came with the fast idle screw, screwed just about all the way in. The Idle Screw was screwed in about 1/2 way. The Mixture screw was at about 1 and 1/2 turns out, as per the book. After many hours of what I would call Learning Time, I got things adjusted so it runs pretty smooth, or as smooth as possible, I also adjusted the timing to spec.

When Warm. The Choke Plate doesn't seem to open all the way, and if I manually open it up all the way, the engine gets rough. If I close the choke plate as far as I can, the engine gets rough, somewhere about the middle of that travel, the engine smooths out nicely. I adjusted that plastic nut-like thing to limit the travel to where the engine runs best. I have the idle set at about 750 RPM. The Idle mixture screw seems to be way out.

It's my understanding that when the car is cold, and I start it, it should go into a Fast Idle mode, then when it's warmed up to normal operating temperature, it runs at normal idle, which I believe should be around 550 RPM, as per the book... I have it at about 750 because that's what the engine seems to like best. The throttle plate should be wide open? Is this somewhat correct?

I thought at first, it's just a one barrel carb, how hard can it be to tune it up? Anyway, any help or tips regarding the tuning of this single barrel carb will be greatly appreciated.

[Groover]

John,

If you have the book, then that's the best place to start. I'm not too familiar with the one barrel, but the book should tell you where to set the auto choke (probably either 2 lean or 2 rich) but if you put it right in the middle it should be good enough to start). When the engine is cold the plate should be just slightly open and when it's fully warmed up, it should be wide open (or nearly wide open). So you could just adjust it either of those ways (almost closed when cold, or twist until it's wide open when warmed up.

There are others here who know far more than I do, but I'd say from what you're saying if it runs best at 750 rpm idle, that makes me think maybe you have a vacuum leak (higher RPM masks it). Pops always says to cup your hands over the choke plate area with the car running, and if the engine doesn't die, then you have a leak (air is getting in somewhere other than through the choke plate).

Does your carb have a draft tube for the choke (a small tube coming off the manifold to bring warm air into the choke area)? If so, make sure that's not plugged up. If it is supposed to be there, and it's missing, then you'll be drafting cold air right into the choke which will take longer for it to warm up.

The high idle cam should be kicked in when the engine is cold and as the choke plate opens and you give it a little gas, the coil will release and let the high idle kick out. The book should fully explain how to set it. There are so many things there I wouldn't want to guess. I do have the same book though so if you're having trouble with specific settings, I might be able to interpret.

Keep us posted.

[1964Comet404]

Thanks Groover... yep, i have the instructions and although I believe I'm doing things right, things don't turn out that way. I didn't have much understanding about the operation of the carb to begin with, and now... I would say things are little less fuzzy. Your explanation about how things work with the fast idle connected some dots for me. I really appreciate that. I don't have a vacuum leak as I installed a vacuum gauge so I can monitor the vac as I go along adjusting things. I just got the car in July, and one of the first things to go was the old rubber vacuum hoses. I'm a big fan of monitoring vacuum on my engines. I even have an old Mile-O-Meter that I will be installing soon. I set the idle at 750 because the engine just seemed to be happier there. I got the car to idle at 550, but she seemed to be a bit sleepy there. I chose 750 simply because the chevy lumina I just recently parted with, idled at that number.

Yesterday she started very rough, but she started and kept going, although in a sickly manner. I believe the Fast Idle screw was out too far. I printed out the instructions for adjusting the carb. Some of the adjustments are "Bench" adjustments. But I checked those before I installed the carb. I'm sure there's something not tweaked right and that it's just a matter of getting things balanced in a Zen or Feng Shui sort of way. I also believe the valves need to be adjusted, so I can't blame everything on the carb, but I feel, valves or no valves, the carb still needs to be adjusted properly. I'm going to recheck whatever I can by way of the book, and using the drill bits to check specs with and all that. I believe the choke plate is maladjusted. I can smooth things out by moving it about by hand.

The Choke I haven't got a clue about. Rich/Lean... what the... I have the thing set down the middle... it seems silly that a couple or so clicks either way are going to do anything... and I'm not sure about it's operation neither... I believe if you turn it counter clockwise the spring gets tighter and when you turn it clockwise it the spring relaxes a bit which I guess either way it changes the resistance of the choke plate... that's what I'm thinking anyway. I'm not sure what that does for anything. I do know that the carb needs to be choked when cold and then wide open or about there, when things get hot.

I was wondering about that fitting on the side of the choke one day, and after investigating things I discovered that it was for like you said, a draft tube. It has a couple of names I think. I saw one at Classic Inlines for $25 bucks. I was wondering if maybe I should install one. I put a vacuum cap over that fitting hole. I thought maybe cold air might be getting in... and also, I believe the cap will help to keep the bugs out, per se. My choke has a hot water heater hose bracketed to it so that the choke heats up as the engine does.

I made some adjustments last night... and thought one of the problems is "Me"... and that although I've read the instructions, my brain gets involved and things don't get done in the right sequence. I haven't been feeling well all day, but I've got a refurberation taking place within myself so in a short while, after I shower, shave, and get all cleaned up to make room for fresh automotive filth... the dogs and I will go out and see what happens when the Comet is Cold. If things go sweetly, the dogs may get a ride over to the fairgrounds for a good romp. Oh... just let me add... that when she's all warmed up, she's running pretty smooth, considering several negative values, but at least as smooth as I believe it's possible to get. As I'm adjusting the idle mixture, which is what I believe I'm doing, I look at the carb return spring, and use it's vibrating wiggle factor as a guide. Oh, another thing, can a leaky exhaust manifold cause issues with the smooth operation of my engine. The previous owner did a heck of a job wrecking that installation... although he was very proud for having done the job himself. My dog could have done a better job. Anyway, that's a story for another day.

[Tristan]

I was just about to post this same question but you have a one up on me since I do not have the book nor the instructions. I can get the thing to fast idle either and I haven't quite gotten the rest of the adjustments figured out either. So I will be watching this thread closely to see what advice you get or what you manage to figure out.

[1964Comet404]

I was just about to post this same question but you have a one up on me since I do not have the book nor the instructions. I can get the thing to fast idle either and I haven't quite gotten the rest of the adjustments figured out either. So I will be watching this thread closely to see what advice you get or what you manage to figure out.

Hey Tristan, I haven't abandoned this thread and I have been PAINstakingly working on my carb adjusment issues. I'm getting it slowly. I'm very, very, close to the goal... last night it was freezing out and she started up pretty good. I Have gotten a better curb idle out of her, and overall I'm just about satisfied... I'm going to try setting everything to spec, which is about 500 RPM give or take 50, so it seems, Automatic Tranny in Drive (block all the wheels, put the emergency brake on, be careful... or get a helper). OH! ...and here's something to watch out for... linkage for my choke/fast idle, was being jammed up a bit, so the Fast Idle wasn't dropping off when it was supposed to... SO, luckily before Insanity settled in, I accidentally hit the choke housing with my screw driver, then... "clunk"... it pops into curb idle... the moral of the story being, make sure your linkage is all free to play while making your screw driver turns... and don't forget about that little plastic nut thing, I had to play with that too, apparently it limits the travel of the choke plate. Mine is set about 1/4' below the top of the screw/shaft right now. Maybe I'll take a pic or two of my carb settings and post them when I'm done. Well, I guess we dont have switches, sensors, and computerized junk to annoy us with our engine repairs and maintenance, but we do have Carbs...

That's some fine sheet metal you got there. Is that a '65 on the left... future project? The only thing better than an old Comet is 2 or more Old Comets... even if they are being used as lawn and garden art.

Ps. seems no matter what I do, I can't get this board to send me notifications, but I will be attending to this thread accordingly.

Ps. I'm ordering a new distributor and I have to find out what size opening there is on the shaft for the oil pump rotor. Apparently, for the '64 model year on the 200, it could be 1/4" or 5/16"... so I have to pull the distributor to find out... unless somebody can tell me there's a way of getting that info from reading the code stamped on the distributor.

Later!

[Tristan]

Reading your post gave me the motivation to do some more searching and I found enough info on the carb to identify other parts on it. That motivation got me out there tinkering even after having surgery on both of my feet last week. That being said I was able to attempt finishing up the adjustment. A few turns on that fast idle screw and a quick trip down the road confirmed my settings! Curb idle is at 500ish RPM and fast idle is at about 750 RPM. Once I get my vacuum gauge hooked up to it, I'll iron out the rest of the adjustments.

You mentioned my 65; that car has been in my family for at least 30 years and was my Dad's first car and the first memory I can recollect is riding in it. Ever since it has been my dream car. Unfortunately it was parked in 1992 and by the time it was passed to me, there was more rust than there was car. For the most part the front clip is solid and so is the drive train. I plan on using the body o the 64 to move everything good I can over and make it as much of my dad's car as I possibly can.

[1964Comet404]

I think my automatic choke is botched up... and it's not choking all the way, and I think when the engine is cold and you give the peddle a stomp, the fast idle cam drops down on that screw which gooses the throttle to fast idle... and then when things warm up, the choke mechanism/t-stat/spring relaxes and the choke plate opens up slowly till the engine is fully warmed up and then opens completely... and when you hit the gas peddle again, the fast idle cam releases and the carb goes into curb idle mode... that's about what I'm believing...

Mine doesn't seem to be choking all the way, so it's not dropping down the fast idle cam, and so, not fast idling... fast idle should be about 1500 rpm... with my fast idle screw all the way turned in, I don't get near that... I have to turn the curb idle screw in a bit to keep it running when cold, but then when the engine warms up, because I turned in the curb idle screw to rescue the fast idle, the curb idle is then too high. So I played with the choke a bit and I'm going to see what happens... but I may be in Autozone tonight getting a manual choke kit, ...and that'll be the name of that tune!

I love hearing stories like yours about some car that's been in the family for a hundred years, and belonged to your dad, and you were born in that car while rushing to the hospital in it... lot's of rust huh... maybe you can get the rust treated or converted... have you ever her of that stuff called POR-15... it's worth looking into I think... it'd be a lot of work transfering over Dad's parts to another car... a lot of work... removing the parts from the receiver car removing the parts from the donor car, then installing the parts onto the receiver car.. that's a ton of work... would be nice if you could "chemically restore" Dad's car and call it a day. Whatever you do, I think you should get Dad's car rolling again... it's a must-do... I envy you... to have such a legacy project... a project that comes from and is all about, your heart and soul...

[Tristan]

It sounds like you've possibly gotten your problem figured out and a manual choke would take a lot of the guess work out of it.

As for my dads old car, there is not enough of the body left that can be fixed. Its way beyond por15, I've looked into it. I really wouldn't call the body structurally sound. My picture is very deceiving. The driver side is pretty well gone. Nearly everything I touch from the doors back falls off or apart and even the sub frame is falling out. I really wish I could rebuild the body.

[Tristan]

Now i'm thinking my linkage in that area is hanging up too. It worked that one time when I posted but ever since then its not right. The choke isn't setting right, looks like the fast idle screw is preventing that and i cant get it to do right.

[1964Comet404]

Now i'm thinking my linkage in that area is hanging up too. It worked that one time when I posted but ever since then its not right. The choke isn't setting right, looks like the fast idle screw is preventing that and i cant get it to do right.

Along with my Fast Idle not fasting, I'm also still not getting notifications from this board no matter what I click "On".

I had the same exact problem!!! I've looked at bunches of carbs on the internet, the 1100's of course, and they all seem to have the FI Screw just about all the way in. Playing with an 1100 in my teeny tiny little metal shed/shop, and what I found was, if that screw is in too far, the FI Cam and it don't get together, and things get a bit jammed up, and you don't get the Fast Idle, which is really just the mechanism opening the throttle a bit while the car is warming up. Then, after the car warms up and the choke is more open, you stomp on the pedal and the mechanism releases, and the carb goes into curb idle mode, and a different screw for adjusting that.

Well sure enough, the FI screw on my mounted carb was in too far. So I played with it til it was just right, in far enough to do it's job, but not so in that it jams things up... and lo-and-behold... tadaaa! ...Fast Idle in effect! Then I let things warm up real good, and went about tweaking the other screws. The book says the Fast idle should be, I think, correct me if I'm wrong, 1500, and the curb idle should be, I believe 500. The book also said to turn the FI screw in til it just touches the cam, and then back it out a bit.

It's Fun! ...ain't it?

[Tristan]

I wish I had some advice for you on the notification issues. I actually went and tinkered some more the other day myself and got the fast idle back but its sitting at around 900, it still may be turned too far in. I'm glad to know that the gas does need to be mashed in to go to curb idle, I thought something else was wrong. When I leave work in the morning I think I'll follow your post and back the screw out some more and see how it does!