1968 289 No Cold Idle, Dies at Stop - Ford Mustang Forum
 
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post #1 of 14 (permalink) Old 11-02-2009 Thread Starter
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1968 289 No Cold Idle, Dies at Stop

This could be two different but interrelated problems. When I start my car in the morning (it's getting cold outside now), it does not seem to engage the cold idle speed. I have to keep my foot on the gas for a while or it will die, but I can't keep the pedal down steady either, or it kind of sputters and then dies. So I have to kind of pump the pedal to keep it between 1000 and 2000 RPM for a few minutes before it will hold steady. The hot idle is set around 500-600 RPM, as specified in the shop manual, and the cold idle is around 1000 RPM.

Now, after I start driving, it will sometimes die when I come to stop. I try to avoid this by shifting into neutral at stops. It doesn't die very often, but it's rather annoying when it does.

The first problem seems to be an issue with the automatic choke mechanism that engages the cold idle. I've tried pressing the gas pedal slowly all the way down and back up before turning the key, pressing it multiple times, and not pressing it at all (when I don't press it at all though, it doesn't start easily).

The second problem, and perhaps tied to the first one, sounds like it might have something to do with fuel, maybe the fuel pump? I have a new filter on the carb, and an inline filter, and the fuel has been clean so far. I don't know what state the pump is in though.

Any ideas? Thanks in advance!


1968 Ford Mustang coupe, 289 V8, C4
URL: ben.farhner.com/mustang
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post #2 of 14 (permalink) Old 11-03-2009
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If it were me id just slap an edelbrock on and call it a day. I could never get mine to run right in the winter but just doing simple adjustments with the fuel and choke worked alright for me.


1966 Mustang- "Five liter Fury"
Wimbledon white with guardsman blue stripes
Ford Racing 302 gt40 aluminum Heads, e303, Edelbrock rpm intake, edelbrock 600, All Forged, 1.6 roller rockers. 340 hp, Ford racing t5 super duty,
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post #3 of 14 (permalink) Old 11-04-2009 Thread Starter
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Edelbrock doesn't offer 2bbl carbs, does it? I'd have to replace the intake manifold too, in that case, which makes for quite the expensive fix. Though I may upgrade one day...

1968 Ford Mustang coupe, 289 V8, C4
URL: ben.farhner.com/mustang
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post #4 of 14 (permalink) Old 11-04-2009
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I'm far from a Mustang carb expert, but a few things I'd check:

- Does the choke plate close properly when the engine is cold?
- Does the fast idle cam engage properly?
- Is the idle jet clogged?
- Do you have a vacuum leak anywhere?

That last one might be the first one to check. Vacuum leaks can cause all sorts of havok. Some possibly-helpful info:

Engine Vacuum Leaks
Tuning Engines

Good luck!

1967 coupe - 289 "Sports Sprint" package - vinyl top - power disc brakes - AC - deluxe hood - 49K miles. Upgraded with Edelbrock Performer intake, Holley 600CFM carb, Pertronix ignition, Tri-Y ceramic headers, Opentracker street suspension. 'Twas Nana's car, RIP.
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post #5 of 14 (permalink) Old 11-05-2009
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Is the automatic choke thermal or electric?

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1967 Mustang Convertible - 289-4V w/C4
1992 Bronco - 302 EFI Auto
1974 24' Lyman Biscayne
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post #6 of 14 (permalink) Old 11-05-2009 Thread Starter
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It's a thermal automatic choke, and unfortunately, I can't seem to get it adjusted so that it's fully closed when cold and fully open when hot. So it's always just kind of mostly open :/ Yes, an electric choke will probably be in my future. (Then I won't have to worry about the choke tube cover either, which is melting :p)

I haven't done a conclusive test, but I don't believe the idle cam is engaging. I can manually set it from under the hood... but that's not too helpful.

I recently removed and replaced the front bowl of the carb to fix a separate issue, so everything accessible from inside the front bowl has been cleaned, the float level is set, and the inlet jets were sprayed out with carb cleaner. (I'm not sure exactly what the idle jet is, though...)

I'm not 100% sure I have no vacuum leaks, but I just replaced the PCV valve, grommet, and host, and the vacuum line from the carb to the distributor vacuum advance. Except for the vacuum line to the tranny (which I have not checked), the rest of the lines are plugged. I'll take a look at those links and double-check what I can.

Thanks guys, hope I can get her running smoothly soon!

1968 Ford Mustang coupe, 289 V8, C4
URL: ben.farhner.com/mustang
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post #7 of 14 (permalink) Old 11-05-2009
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Quote:
Originally Posted by macgeek View Post
(I'm not sure exactly what the idle jet is, though...)
I think maybe "idle port" is a better term. It's an alternate fuel pathway used when the throttle plates are closed (at idle). It allows a small trickle of fuel to flow into the intake manifold when airflow through the carb is relatively small.

This page has some pictures that give the general idea.

If the idle port is clogged, no fuel at idle and engine dies. If you sprayed everything out with carb cleaner, you're probably OK, but it's something to keep in mind if everything else checks out.

I would buy a vacuum gauge and give your system a check. They're not very expensive and they're very useful for diagnosing problems.

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It's a thermal automatic choke, and unfortunately, I can't seem to get it adjusted so that it's fully closed when cold and fully open when hot. ... I don't believe the idle cam is engaging.
If you adjust the choke so it's closed when cold, and manually engage the fast idle cam, does the car start and run smoothly? After it warms up, if you manually hold the choke fully open and disengage the fast idle cam, does it continue to idle smoothly?

If the answer to both questions is yes, then I think your idle ports are fine. The fast idle cam and choke-not-fully-closed problem might impact cold operations, but after warming up I don't think a slightly closed choke would cause significant problems (slightly = 10 or 15 degrees from vertical). It'll run maybe a little rich but it should run OK.

So if it idles OK when cold (and manually configured for cold operation) and idles OK when warm (also manually configured), but still dies after going from cruise to idle, that makes me go back to vacuum. I had a 1976 Ford (yes Ford) Capri P.O.S. in high school that I could not get to run steady until I tested vacuum at each and every hose. Turned out one of the smaller ones somehow got plugged with gunk and was causing havoc. Looked fine on the outside, but caused problems with smooth running. That was a California car, too, so double the usual number of vacuum hoses for smog.

This is all just general-purpose carb troubleshooting, I'm afraid. My car's in the shop 1500 miles away so I can't provide specifics for Mustang carbs. Except what I find on the web...

Good luck.
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1967 coupe - 289 "Sports Sprint" package - vinyl top - power disc brakes - AC - deluxe hood - 49K miles. Upgraded with Edelbrock Performer intake, Holley 600CFM carb, Pertronix ignition, Tri-Y ceramic headers, Opentracker street suspension. 'Twas Nana's car, RIP.
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post #8 of 14 (permalink) Old 11-09-2009 Thread Starter
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Well she seems to idle okay once I get her warmed up, but I'll do a little diagnosing on the carb.

I'll try to pick up a vacuum gauge this week and go over the engine.

Thanks all

1968 Ford Mustang coupe, 289 V8, C4
URL: ben.farhner.com/mustang
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post #9 of 14 (permalink) Old 11-10-2009
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1968 289 No Cold Idle, Dies at Stop

Hello my friend,
it has been awhile. Because I am familiar with your carb and previous troubles
I think you have a choke setting issue. A vac gage is a great tool and I recommend it.

To check the choke action do this on a Saturday or at a time when the car is cold and you have a few minutes to experiment.

Step on the gas pedal once. Press it fully and release. Just Once.

Remove the air cleaner and look at the choke plate (butterfly).
It should be almost closed. If it is great...then see if the screw on the pass side (fast idle cam) is engaging the cam. Start the car and see what type of speed you think she is at. Adjust to where you think she is at about 1800rpms cold.
The watch the action of the choke to see if it starts to open after about 20 seconds.

I am pretty sure your choke is not set right.

Your fuel pump is fine..don't worry about it. The issue is minor and can be fixed it just will take a little playing with the choke.

Send me a PM if you have further questions

Be well my friend........ Print Dad
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post #10 of 14 (permalink) Old 11-12-2009 Thread Starter
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Thanks, Print Dad. I did some tweaking with the automatic choke, and now it seems to be working! Not sure why it wasn't before, but after some adjustment, it engages the cam when cold, giving me fast idle. I think my butterfly valve may still have some problems though; it doesn't seem to open very freely, but eventually does.

I did pick up a vacuum gauge and it was reading pretty steady around 18", with very slight occasional variation (less than 1")

So for now, anyway, I think the problem is solved. Thanks guys!

1968 Ford Mustang coupe, 289 V8, C4
URL: ben.farhner.com/mustang
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Excellent!

1967 coupe - 289 "Sports Sprint" package - vinyl top - power disc brakes - AC - deluxe hood - 49K miles. Upgraded with Edelbrock Performer intake, Holley 600CFM carb, Pertronix ignition, Tri-Y ceramic headers, Opentracker street suspension. 'Twas Nana's car, RIP.
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1968 289 No Cold Idle, Dies at Stop

Hello macgeek,
Sorry for the delayed response.
My wife and I have been cruising a lot before the snow.

I am glad to hear things are going better.
Great to hear the vacuum numbers. They tell a lot about the condition of the motor.

As far as the butterfly, make sure there are no tiny burrs on the plate that could stick slightly.

See how she does and then we can try again.

Isn't it great to fix something yourself? Well done.

Be well my friend....... Print Dad
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post #13 of 14 (permalink) Old 11-15-2009 Thread Starter
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Thanks, Print Dad.

Well, so far, she seems to be engaging the cold idle cam about half the time. Perhaps I'm simply not pressing the pedal down far enough?

Also, when it fails to engage the cam and starts up at hot idle speed, it sputters and dies the first couple times (this doesn't happen with the cold idle). Oddly, if I try to prevent this by giving it some gas to bring it up to cold idle speed, it still sputters out and dies. I'm thinking I may have a fuel mixture problem?

Thanks again, everyone!

1968 Ford Mustang coupe, 289 V8, C4
URL: ben.farhner.com/mustang
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I had a problem once when my car would not idle well and died when I stopped at the stop light . Turned out to be a float level too high and when I stopped the gas would slosh over into the venturi and flood the engine.
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