67 Impala stuck idle - Impala Tech
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post #1 of 6 (permalink) Old 04-30-2016, 02:46 PM Thread Starter
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67 Impala stuck idle

I'm having an issue with my idle being stuck. This only happens when I'm in park. The other day I pull into the garage, switch to park, and the tachometer is at 1,500 RPM (running fast) which always happens. I then go to tap the gas like I usually do to slow it down to 500-1,000 RPM before shutting it off. Instead it jumps up to 2,500 RPM and gets stuck which scares the hell out of me. I'm panicking trying to figure out what's happening, not wanting to tap the gas again I switch to reverse or drive and it slows back down to 500 RPM. I then switch back to park and shoots up to 2,500 RPM again (same with neutral). I have no choice but to shut it off while in park. Everything starts shaking with the exhaust bellowing and screeching. Then it's quiet with heavy exhaust fumes.

Any idea what's going on?

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
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post #2 of 6 (permalink) Old 04-30-2016, 03:20 PM
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Fast Idle Cam associated with your choke mechanism is sticking.


You didn't mention what type of carb you have or whether it


A picture is worth a thousand words.


Big Dave
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post #3 of 6 (permalink) Old 04-30-2016, 03:33 PM Thread Starter
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I have a Rochester 4 barrel. It was rebuilt last summer but I haven't driven the car very much since then. I noticed the idle has been sticking a little bit since then but this is the first time it was really noticeable.

Could you elaborate more one what exactly might be happening? Thanks.

Not at home right now so I'll have to get a picture later.

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
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post #4 of 6 (permalink) Old 04-30-2016, 08:49 PM
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Quote:
Originally Posted by Classiccarman View Post
I have a Rochester 4 barrel. It was rebuilt last summer but I haven't driven the car very much since then. I noticed the idle has been sticking a little bit since then but this is the first time it was really noticeable.

Could you elaborate more one what exactly might be happening? Thanks.

Not at home right now so I'll have to get a picture later.
On the top of carburetor is a flap that cuts off air (chokes it). That flap is controlled by either a bi metal strip wrapped in a coil found inside an electric choke canister (seen on the sides of Holley or Carter carbs as an aluminum housing with the other half being made of black plastic). Or your carb will have a rod that goes down to the fast Idle cam on the passenger side of the carb that has other rods that go to a little box bolted to the intake or connected by way of the throttle linkage to the accelerator pedal.

This cam is weighted so that it will fall open when the rods agree your car has warmed to a point to retract that rod attached to the flap up top. The cam has a secondary idle speed adjustment screw and a few other features that most ignore up until it stops working.

One thought that occurred to me as I was going through the linkage that makes your choke work is of course your motor mounts.

Ralph Nader who couldn't extort any money from GM in his campaign of terror on the Corvair, discovered that Chevrolet V8 engines were experiencing problems with broken motor mounts. They were first introduced in 1958 for use with the 283 (the Power Packed) replacement to Chevy's first V8 in 1955 the 265. With the introduction of the 327 those 283 mounts were tearing apart. Chevy had already produced a fix for this problem as the 348-and 409 made quick work of breaking the motor mounts. So Chevy already had a fix in the pipeline. Of course Ralph Nader knew this and realized he was going to loose money again if he didn't act fast so instead of suing GM to get the money he wanted in court he went to the public and again smeared GM in the press and at Congressional hearings in another attempt to extort money. Instead Congress mandated a settlement that created the first ever product recall. They had GM recall every car made since 1958 in 1968 and fix the problem by putting a five ton steel wire sling around the upper A-arm mount that tied into the stock cast iron exhaust to keep the broken motor mount from allowing the motor to roll over. When it rolls it pulls the throttle open and engine torque keeps it open until the engine is turned off.

If you have tubular headers or your car was never repaired (very few people ever took their car in to the dealer ship to have it fixed) or if the wire has rusted away your motor might be having a broken motor mount problem. It is easy to test. Have some one plant their foot firmly on the brake while they give the car a little gas. You stand BESIDE the car with the hood raised and watch the engine. If it rolls over then you have discovered your choke problem isn't the choke at all.

You now have another problem that you can thank Ralph Nader for. Your motor mounts are different from motor mounts made after 1969 when GM was told what to do by Congress. Congress dictated that the replacement motor mount couldn't fit your car (hence the wire sling patch instead of a replacement 348-409 motor mount). The old style motor mounts are only sold through a restoration house as opposed to what sits on the shelf at your corner auto parts store. His computer says it fits all Chevy V8 engines, but it won't fit. You would have to pry it apart to get it to fit over the stand and the bolt hole won't line up after you do that not to mention you have already started to rip apart the rubber bond that holds it together. You can buy an interlocking rubber motor mount for a BBC but it would have to be for a 348-409 if your car is newer than a 1968. If you have a 1958 through 1968 you can also buy a polyurethane interlocking motor mount but purists hate the idea of not having the original defective parts on their car.

If your motor mounts are in good shape (the motor stays put under the torque test). I will post some pictures of how to adjust the choke on your carb.

Big Dave
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post #5 of 6 (permalink) Old 05-01-2016, 02:38 PM Thread Starter
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Interesting. I'll take a look at that as soon as possible. I don't think it was ever recalled because when I first bought it in 2010-2011, I took it to my mechanic to have a check up. He gave me a little list of parts it needs. The motor mounts were perfectly fine then but he mentioned something about how they don't have 'flip restraints.' The only ones we were able to find looked cheap/cheap thin metal compared to the originals so we didn't bother with it. This is back when I was a rookie by the way and didn't know where to look for parts. Those motor mounts I found were from NAPA and I returned them right after my mechanic criticized them.

My father did tell me a story before about somebodies engine flipping and trashing the car.

1967 Chevrolet Impala 4 door "post" sedan
327 5.4L V8 - 3-speed TH350
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post #6 of 6 (permalink) Old 05-13-2016, 07:05 AM
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That car originally had a throttle ROD, not a cable. If it is still the rod, try lubing the pivot points at the firewall lever and carb. Also, look for anything that may be touching/dragging on the rod, IE, power brake hose, spark plug wire, etc.

Also, and I've seen this a number of times, if you have a floor mat, make certain it isn't interfering with the pedal. If the carpet has been replaced, check the heal pad, they aren't always in the correct location and can catch the bottom of the pedal and hold it.

On the subject of the pedal, it pivots on 2 studs at the bottom, they may well be rusty and holding the pedal. The pedal should pop off those studs by lifting gently to clean, lube them with lithium grease.

'62 Impala SS 409 TH350
'66 Chevelle SS 496 M20
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'67 Camaro ss/rs 350 PG
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