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Trouble under the hood.


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I have a 1971 MACH 1 with a 351 Cleveland 2 barrel carb. Recently it started idling EXTREMELY roughly while in gear. It idles fine when it is in park or neutral, but not in any gear. I removed the distributor cap while investigating, sanded the points and cap/rotor contacts, and lost all but the most intermittent spark (verified with a timing light). I put on a new distributor cap, rotor, points, and condenser. The car then exhibited the same condition, idling in neutral but not in any gear. I have since changed the plugs (all of which looked really good except number 3, which looked wet) and the wires. The same condition exists.

I have checked the idle with a dwell tach, and it shows 600 rpm in park, which immediately drops to 480 rpm when placed in gear. If I manually increase the speed to 600 rpm, the idle smooths out and the car sounds normal. If I turn up the idle while in gear, it then increases to between 900 and 1,000 rpm when placed back in park.

The car does have factory air conditioning (which is disabled now) and therefore an idle speed increasing solenoid. I have not seen this activate when the car is placed into gear. Does anyone know if this is supposed to increase the idle speed when the air is not on but the car is placed into gear? Does any have any other suggestions?

1971 Mach 1

351 Cleveland

Driving-1.jpg

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600RPM while in gear w/ brakes on is good. Going up to 900-1,000 when in PArk isn't bad.

 

I'm sure someone more knowledgeable than me will come along, but it sounds like you just need to increase your idle a bit and be happy at 900-1,000 in Park and 600 in gear.

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6000RPM while in gear w/ brakes on is good.

 

That does sounds like a good time lol

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97 F150: wrecked, 96 Dodge 4x4: blown motor / donated to the base

88 Suburban 4x4 355 cid 8 inch lift: sold, 95 Celica 5 speed : sold

68 F750 391 cid : sold,  96 F350 7.3 diesel dually : sold

86 Chevy 1500 305 cid c1500: sold, 73 Mustang mach 1 466 cid 5 speed : under construction

89 F350 4x4 cummins swap : sold, 64 Dodge d600: gone

00 Excursion: traded, 72 Mustang mach 1 302: scrapped

73 Mustang coupe: scrapped, 73 ranchero gt

06 Honda crf 450x : sold, 04 Honda vtx 1800

88 Bronco xlt lariat: sold, 76 Charger: traded

95 F350 4x4: sold , 91 Crown Victoria 302: sold

02 Dakota: traded, 96 f250 powerstroke: parts truck

87 f700, 98 e350 powerstroke: sold

03 land rover: traded, 95 f350 dually: part out

95 f350 dually: traded, 94 f150 4x4: traded

97 f250: sold, 76 Maverick 302: sold

91 240sx rb25: sold, 86 firebird: sold

86 Trans Am: sold, 88 westernstar: sold

89 dodge d350: sold, 2000 Dakota 4x4: sold  

84 f350 3+3: sold, 90 bronco: partout

67 catalina, 64 chevy c60

64 jeep j200, 74 corvette stingray

79 Lincoln mark V, 2013 f350: goldilocks

 

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verdelizard,

 

The idle speed increasing solenoid should activate when you switch on your A/C. Do you have a Vacuum gauge? You can check your fuel and air mixture settings. It might not hurt to check you vacuum lines and caps. They can dry rot and crack cause idling issues. Let us know what the outcome is!

 

mustang7173

Thanks,

mustang7173 🇺🇸

"Courage is being scared to death but saddling up anyway" -- John Wayne

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The car does have factory air conditioning (which is disabled now) and therefore an idle speed increasing solenoid. I have not seen this activate when the car is placed into gear. Does anyone know if this is supposed to increase the idle speed when the air is not on but the car is placed into gear? Does any have any other suggestions?

 

Do you have an automatic transmission? I suspect you do. If I'm not mistaken, there's a set of linkages that comes of the transmission that is tied to your throttle, it's supposed to bump the throttle when you shift to deal with the added drag that the torque converter puts on the engine. It sounds like yours isn't being given the bump it needs and so your RPM's are falling

2013 Ford Focus SE Flex Fuel 5spd - Daily Driver

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Check for large vacuum leaks.

 

The solenoid is not for the AC. It is an anti-diesling solenoid. It Should activate when the ignition is in the ON position, regarless of the AC being on.

 

There is no linkage between the transmission and engine that increases the throttle when you put the car in gear.

 

Put a vacuum gauge on it and post up vacuum readings at idle in park and in gear. As well as what the needle is doing.

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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or your vacuum modulator hose is cracked or the modulator itself is bad causing a vacuum leak. You can use any number of sprays to identify vacuum leaks, carb cleaner is probably one of the better choices, concentrated skunk scent is probably not ;)

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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verdelizard,

 

Will e is correct. Sorry, I was thinking more of the idle speed solenoid.

 

According to the Ford Master Catalog, the Solenoid assembly D3AZ-9D856-A (351 - 2 bbl) is an idle Stop Solenoid

 

An electrically operated plunger in a carburetor that provides a predetermined throttle setting at idle and closes the throttle completely when the ignition switch is turned off. Also known as anti-dieseling solenoid.

 

I also found this information for a Idle speed solenoid-This is FYI only.

 

The idle speed control solenoid controls the idle of the engine when the air conditioning is engaged. Since the ac pump draws down the engine idle the solenoid increase the idle when the ac is on.

 

So, It is possible that the idle stop solenoid device has stopped working properly.

 

mustang7173

Thanks,

mustang7173 🇺🇸

"Courage is being scared to death but saddling up anyway" -- John Wayne

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The anti-diesel solenoid is easy to test. Apply 12v positive to it and see if the plunger moves. It can be adjusted (and the idle speed with it) by turning the assembly.

 

But I doubt this is your problem. In my experience if the engine runs fine in park but crappy at idle there is a vacuum leak. Usually the hose/pcv assembly.

 

What would help us is if you can post:

1. Initial timing at idle in park and in gear with the vacuum to the distributor attached.

2. Initial timing at idle in park and in gear with the vacuum disconnected. (plug the line)

3. Manifold vacuum at idle and at park. (with the vacuum connected to the distributor) and let us know what the needle is doing. Is it steady?

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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I'll bet you turn your phone on vibrate, put it in your front pocket then call yourself... Often... ::rofl::

 

I thought he posted 6000 rpm with the brake on indicating a burn out lol

2cossj6.png

97 F150: wrecked, 96 Dodge 4x4: blown motor / donated to the base

88 Suburban 4x4 355 cid 8 inch lift: sold, 95 Celica 5 speed : sold

68 F750 391 cid : sold,  96 F350 7.3 diesel dually : sold

86 Chevy 1500 305 cid c1500: sold, 73 Mustang mach 1 466 cid 5 speed : under construction

89 F350 4x4 cummins swap : sold, 64 Dodge d600: gone

00 Excursion: traded, 72 Mustang mach 1 302: scrapped

73 Mustang coupe: scrapped, 73 ranchero gt

06 Honda crf 450x : sold, 04 Honda vtx 1800

88 Bronco xlt lariat: sold, 76 Charger: traded

95 F350 4x4: sold , 91 Crown Victoria 302: sold

02 Dakota: traded, 96 f250 powerstroke: parts truck

87 f700, 98 e350 powerstroke: sold

03 land rover: traded, 95 f350 dually: part out

95 f350 dually: traded, 94 f150 4x4: traded

97 f250: sold, 76 Maverick 302: sold

91 240sx rb25: sold, 86 firebird: sold

86 Trans Am: sold, 88 westernstar: sold

89 dodge d350: sold, 2000 Dakota 4x4: sold  

84 f350 3+3: sold, 90 bronco: partout

67 catalina, 64 chevy c60

64 jeep j200, 74 corvette stingray

79 Lincoln mark V, 2013 f350: goldilocks

 

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There is no linkage between the transmission and engine that increases the throttle when you put the car in gear.

 

There is a linkage that goes from the Transmission to the Carb, but after doing a little more research I realize it doesn't work like I thought it did.

 

I'm speaking of the Transmission Kickdown Link, which is there to make the car drop a gear when you stomp on it. I thought it went the other way around (transmission affecting the carb not the carb affecting the transmission)

 

My apologies for any confusion this has caused!

2013 Ford Focus SE Flex Fuel 5spd - Daily Driver

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I always thought it was normal for my idle to go from about 900 down to 600 when putting it in gear with the brakes holding her still.

 

Can someone help me identify the selinoid that bumps up the idle? I think I need to test mine.

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I always thought it was normal for my idle to go from about 900 down to 600 when putting it in gear with the brakes holding her still.

 

Can someone help me identify the selinoid that bumps up the idle? I think I need to test mine.

 

The only solenoid that I remember seeing on my car was on the drivers side front of the Carb inline with the throttle linkage. The rear of mine was smashed off and I couldn't find a replacement so I don't have one installed at the moment.

 

Are you still running a stock carb?

2013 Ford Focus SE Flex Fuel 5spd - Daily Driver

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or your vacuum modulator hose is cracked or the modulator itself is bad causing a vacuum leak. You can use any number of sprays to identify vacuum leaks, carb cleaner is probably one of the better choices, concentrated skunk scent is probably not ;)

 

Where can I find me a can of that Jeff?

2rr7aiv.png

 

Just cruising along minding our own business when BAM!!! The LAWS show up.

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I always thought it was normal for my idle to go from about 900 down to 600 when putting it in gear with the brakes holding her still.

 

Can someone help me identify the selinoid that bumps up the idle? I think I need to test mine.

 

The only solenoid that I remember seeing on my car was on the drivers side front of the Carb inline with the throttle linkage. The rear of mine was smashed off and I couldn't find a replacement so I don't have one installed at the moment.

 

Are you still running a stock carb?

 

I have an Edelbrock Thunder Series 650CFM. The only selenoid-like thing I see is for the choke.

350-18064_1.jpg

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It looks like this:

 

0900c152801c841d.jpg

 

Not all carbs have them.

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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