Throttle Got Stuck Open

[jas280z]

I just completed swapping an Edelbrock 1406 600CFM carb and 2V to 4 barrel Edelbrock intake on my 1971 Mach 1 (351C 2V). I used the Edelbrock throttle cable relocation bracket (PN 1493) and the Edelbrock throttle linkage (PN 1483). I also used the Lokar kickdown cable in place of the kickdown rod.

I put about 40 miles on the car with no issues.

Driving this morning, the throttle stuck open after accelerating. I shut the car off and coasted to where I could look at the issue. When I removed the air cleaner I could not see any issue and the throttle appeared to have the full range of motion. The issue was gone and I continued cautiously to work.

I took a closer look at lunch today. I thought possibly the throttle linkage had gotten hung up on the original air cleaner housing. When I flipped the housing over I saw no signs of contact. I put everything back together and stuck my phone under the air cleaner to record the linkage moving. This confirmed that nothing appears to be making contact.

One thing that I noticed is that the throttle cable between the bracket and firewall is kind of looped around, i.e. the cable probably longer than necessary now. This may be a result of the relocation of the bracket, but it seems like there is more loop than the relocation would account for. I see that Lokar makes a cut to fit throttle cable, but that would require getting the Lokar throttle linkage as well.

I took the car for a ~5 mile drive after putting everything back together and had not issues.

Has anyone had a similar issue after a 4bbl swap? The cable moves easily and does not appear to bind when disconnected from the carb. I will likely try lubing the cable. I believe that the original cable is still on the car, I may go with a stock replacement as well.

Any thoughts on anything else that may have gotten stuck? The carb is not new, it was taken off of a project '67 cougar that is getting a crate motor. It appears to be in good working order though, I do not see anything binding on it.

The fact that I did not find a smoking gun has me nervous.

 

[jbojo]

How is the return spring on the linkage, could be worn. I went with the Lokar throttle cable and bracket with there kick down cable and it works very well.

 

[jas280z]

How is the return spring on the linkage, could be worn. I went with the Lokar throttle cable and bracket with there kick down cable and it works very well.

The return spring on the cable is most likely original, like the cable. It appears to be in working order, but it has visible "patina." I do have the Edelbrock kickdown return spring attached as well, which is brand new. This is essentially a second return spring since I am not using the kickdown rod any longer.

I am thinking that the problem has to do with the 4 barrel swap. I put ~1000 miles on the car in the past month (I bought it in very late July) and did not have any issues with the stock setup.

Thanks for the picture, that is a great view of your linkage and cable. If I do go the Lokar route, I will definitely use that as a reference!

 

[Mister 4x4]

I'm using the stock accelerator cable for mine (mine was dirty, but functional - so I cleaned it up and lubed it).

My AOD came with the factory cabling as well, so I fabbed a bracket for it - but it doesn't interfere with the stock accelerator cable.

 

[72HCODE]

i cannot offer a solution in your case; but this was a big reason i went to a holley carburetor setup early on.

I installed an Edelbrock and had the same problem, the throttle cable would randomly hang up at WOT. i also used all the correct linkage Edelbrock recommended. for me it came down to the linkage being too wide and it put the cable and spring at an obtuse angle. this was randomly getting the cable hung up. i found for 70-73 mustangs Edelbrocks caused issues unless you modified the cable bracket moving it out away from the center on the original intake mounts. for early mustangs there is no issue but for the design on our cars it seems to be a problem.

i had other tuning issues with the Edelbrock but when the cable got stuck 2 times and i had to re-engineer to make it work i said forget it and switched manufacturers for the carb. the holley with its ford adapters sits narrow compared to the edelbrock and the cable and spring sits almost as oem so it didn't hang up any more.

many people use the Edelbrock without issues it just did not work for me and i felt it was not going to be right in my mind.

 

[jas280z]

I'm using the stock accelerator cable for mine (mine was dirty, but functional - so I cleaned it up and lubed it).

My AOD came with the factory cabling as well, so I fabbed a bracket for it - but it doesn't interfere with the stock accelerator cable.

Does your stock cable seem too long between the bracket and the firewall? One thought is that the cable may have gotten kinked due to the "s" it does.

I will try to post a picture when I get home from work.

i cannot offer a solution in your case; but this was a big reason i went to a holley carburetor setup early on.

I installed an Edelbrock and had the same problem, the throttle cable would randomly hang up at WOT. i also used all the correct linkage Edelbrock recommended. for me it came down to the linkage being too wide and it put the cable and spring at an obtuse angle. this was randomly getting the cable hung up. i found for 70-73 mustangs Edelbrocks caused issues unless you modified the cable bracket moving it out away from the center on the original intake mounts. for early mustangs there is no issue but for the design on our cars it seems to be a problem.

i had other tuning issues with the Edelbrock but when the cable got stuck 2 times and i had to re-engineer to make it work i said forget it and switched manufacturers for the carb. the holley with its ford adapters sits narrow compared to the edelbrock and the cable and spring sits almost as oem so it didn't hang up any more.

many people use the Edelbrock without issues it just did not work for me and i felt it was not going to be right in my mind.

Interesting. Thanks for the first hand account. The cable does appear to be at a bit of an angle, I don't recall it being too extreme though.

I am hoping to stick with the Edebrock, not only because it was free, but because I would like to go to a Ram Air setup eventually. I read that Holleys do not fit well under the Ram Air housing due to the size of the fuel bowls.

 

[rcadd1ct]

Throttle blades hanging on the base gasket?

Did you torque the flange down evenly?

 

[Jeff73Mach1]

for me it came down to the linkage being too wide and it put the cable and spring at an obtuse angle. this was randomly getting the cable hung up. i found for 70-73 mustangs Edelbrocks caused issues unless you modified the cable bracket moving it out away from the center on the original intake mounts.

I think this is the answer.

You might be able to test by loosening the mounting bolts to the intake manifold for the cable bracket and operating it with pressure towards the center of the motor to try and recreate the sticking open. That bracket should be easy to modify if necessary.

 

[jas280z]

So I dug into it again last night. I was not able to find the issue for sure, but I have not had it happen again... yet.

I lubed the cable and carb throttle linkage. I tried to make sure that the throttle cable run was as smooth as possible, to avoid any kinks.

I also lubed the cable in the passenger compartment. While doing that, I noticed that the ducting off the blower motor was not secured to anything. I pulled it out to be safe. Obviously it would stand to reason that the issue I had was likely a result of the carb swap... but it is possible that the pedal itself was getting hung up on the loose duct. I am not convinced this is the answer, but it would make sense.

I took a whole bunch of pictures. Please take a look and let me know if I may have overlooked anything.

http://imgur.com/a/h6SpM (let me know if the album has issues, it was having a hard time loading for me).

 

[Jeff73Mach1]

I looked at your pictures and my thoughts are that the duct assembly may have bound up the pedal linkage. You'll want to reinstall it properly at some point, but it looks like it might have just been stuffed in place without any mounting bolt.

You appear to have properly relocated the throttle bracket. Because the pivot is ball shaped the minor misalignment that still exists is not likely to be your source of binding. You could use an adjustable crescent wrench to bend it and improve the angle just a bit, or redrill that adapter to allow you to slide it outward another 1/8-1/4 inch. All in all I don't see anything that jumps out and it looks like a nice clean install.

 

[Twins]

Throttle blades hanging on the base gasket?

Did you torque the flange down evenly?

+1. Is it possible the secondaries are catching on the gasket and hanging open?

 

[jas280z]

Throttle blades hanging on the base gasket?

Did you torque the flange down evenly?

+1. Is it possible the secondaries are catching on the gasket and hanging open?

I did torque it down evenly. I don't think this is the issue, but the carb it easy enough to remove that I will take a look.

 

[Bill73Ragtop]

"I am hoping to stick with the Edebrock, not only because it was free, but because I would like to go to a Ram Air setup eventually. I read that Holleys do not fit well under the Ram Air housing due to the size of the fuel bowls."

Just a note here: I've been running with a 600 cfm Holley Street Avenger under my ram air cleaner for a decade with no issues whatsoever.

 

[jas280z]

"I am hoping to stick with the Edebrock, not only because it was free, but because I would like to go to a Ram Air setup eventually. I read that Holleys do not fit well under the Ram Air housing due to the size of the fuel bowls."

Just a note here: I've been running with a 600 cfm Holley Street Avenger under my ram air cleaner for a decade with no issues whatsoever.

Good to know!

 

[1973grandeklar]

I installed a 302 with a Weiand intake and a Holley 600cfm. I used the Holley Ford kickdown shaft so I could keep the rod. But I had the same thing happen to me! The throttle got stuck WOT. I thought I could lube it up and it worked for a while, but then it happened again!

My cable alignment to the ball looked almost exactly like yours. I drilled the cable bracket holes to slot them and moved this out so the cable is directly in line with the ball. I have not had any sticking since. I even swapped the 302 out with a 351W. Used a stock intake with the Holley and had to adjust the cable bracket out to align it perfectly.

What I think happens is the spring on the cable compresses almost completely at WOT. That little bit of an angle binds up the spring. The ball works for swiveling the connection, but it does not prevent the spring from binding up as it is linear on the cable. At least that was my theory and the problem went away with the alignment.

 

[jas280z]

Figured I would give an update to the situation. I drove the car all through fall, putting it away in early November. Since taking it out of storage, I replaced the carb but used the same linkage. I have not had this issue again, since removing the suspected bit of heater ducting.

I suspect that was the cause, and it was a coincidence that it happened right after swapping to the 4 bbl. Hopefully if anyone has a similar issue in the future this post may help them.

Thanks again for all the help and suggestions!

 

[sdstang]

I had the same thing happen with the same carb. Happened once but couldn't figure out what happened. Still being restored so I don't have any time on it to see if it happens again.

 

[tony-muscle]

I had the same issue happened to me with a 4V Holley. Check my thread for pictures: http://www.7173mustangs.com/thread-warning-possibility-of-gas-pedal-stuck

The culprit there was that a plug wire got wedged between the carb linkage at full throttle and the manifold. Obviously the problem is intermittent because it depends on the location of the wire. Easily fixed by fixing the plug wires routing.