Just started driving my "project" ('73 2.0L with 74' F.I. setup) up and down the block for my preliminary road test. One thing I noticed, and my 79 yr. old father really noticed, was the gas pedal was very stiff.

I have already replaced the plastic bushings in the pedal cluster with the brass rebuild kit. Tonight, I disconnected the throttle cable from the throttle body and confirmed the cable / pedal was not the issue. It seems that the supplemental spring on the throttle body is the culprit.

Is there a different, easier spring that I can install or is a stiff gas pedal just part of the normal Porsche engineering? Or, should I look for a '73 throttle body without the supplemental spring?

Thanks - Scott

Make sure that the pedal board is not interfering with the pedal action, move the board as far right as you can.

Not the pedal board... either the spring is the problem or the butterfly/axle itself.

I've got a spare 75 1.8 supplemental spring that you can have to use or compare.
Is it still stiff without it? If the car has been sitting for a long time, the throttle body butterfly may have some corrosion or buildup on it that is dragging.

Kevin

There is a steel piano hinge in the OEM pedal that could have rusted. Try working it back and forth for 5-10 min. You may just be able to achieve an acceptable level of resistance than way.

Not anything to do with the pedal cluster... action is fine when the throttle cable is disconnected from the throttle body @ the throttle body.

Anyone know if there is an "easier" spring? Kevin.... hold onto that 1.8L spring for me.

When you move the TB, with the cable disconnected, does it feel smooth?

TB movement is smooth with and without the cable attached (and I cleaned the TB while it was out of the car to make sure the flapper didn't "stick").

Is a stiff pedal normal? How does the 914 pedal pressure compare to a modern car?

...Sometimes the bushing's in the TB
wear out?
(repair or replace)

I am in this same boat. I am replacing the cable, and the pedal it self to see if that helps. Not sure why the throttle feels so darn stiff compared to other cars.

Most any FLAPS will have throttle return springs. They are a spring with a long attachment wire you can cut it for any desired tension.

It ain't a special "Porsche" spring, so it doesn't cost $100. I think about $3.00 is the going price.

Just to make sure that I'm asking about what everyone is answering about... I'm talking about #4 "supplemental spring" in the pic below.

Click to view attachment

If the the throttle body is lubed and smooth as well as the spring, I'd look back to the throttle pedal linkage. Is it possible that it may be getting into a bind when there is a LOAD on the cable? Can you get someone to apply tension or an independant springload on the cable? Can you vouch for the condition of the cable and it's lube? Ain't much, but it's all I got.....

The spring you are showing was not called the "supplemental" spring. It was the spring on the TB that Porsche initially installed, primary return spring.

The "supplemental" spring was installed from the TB arm to the rear of of the engine tin in case the primary spring broke, allowing for a wide open throttle condition.

That's how I understood it anyway.

Well, I poached this image from PP and they list #4 as the Supplemental Spring (added after the '73 TB which had only a straight arm and no coil spring (www.914world.com/bbs2/index.php?showtopic=108520)).

No matter the name, that spring does what you say Ron.

Still have the fundamental questions: is the 914 pedal action much stiffer than modern day cars and/or does anyone know of an "easier" #4 spring?

Probably a bit stiffer than modern day cars, but the problem is somewhere. I've had stiff ones and really light ones and I can't tell you why. Cleaned TBs, checked angles and rodded out cable tubes.

I can't remember if you rebushed the pedal assembly, but if worn, putting a load on the linkage could cause binding. If not loaded, it would move free and easy.

It should not be that stiff. Maybe a little stiffer than a new car. My 74 2.0 is very smooth.

Click to view attachment

Isn't it amazing that most everyone misread you first post? The pedal cluster is NOT the prob. I've seen the same prob with many late model cars. Get a throttle body from a 73.

Just because the cable moves freely when disconnected and testing by feel with your hands doesn't mean the cable is ok. They can (and do) wear on the inside and not be affected unless there is tension (as there is when it's installed) on the cable. I've seen just the very slightest bend in the threaded end of the cable cause serious binding with the cable installed and under tension but not when testing by hand and unconnected.

Well, I do have a spare throttle cable to replace the one I have. Looks like I have a new project for tomorrow afternoon.

Perhaps the spring was wound an extra turn tighter by the PO to compensate for a worn and binding cable. Also if there is a sharp bend in the cable routing you could see more resistance. The clutch linkage rides what a 1/2" from the throttle, perhaps the lines are crossed.

Does the throttle return to idle easily or does it hang up?

I would start with the easiest first, make sure that the spring isn't on too tight, 2nd, check out the cable routing for sharp bends, 3rd option would then be the cable itself.

Good luck,

the cable also comes into contact with the coil if it is routed wrong and can become a ground wire..that melts the cable housing.

Replace the cable..its gonna break anyways...you may as well know its new.
Buy two..keep one in the car....they do break at the worst times.

For the throttle body..remove everything except the shaft and the brass plate. It should be super smoot in operation.
If the plate is out of adjustment...and it can be adjusted by moving it a hair in either direction, it will rub on the inside of the throttle body and can create a problem.

Clean clean clean...brake cclean and a brass brush, or dunk the whole thing in carb cleaner for the night...it will do wonders.

You state that its not the pedla...just check.
The pedal is part of the return spring function and it has a spring imbeddded in the base of the pedal that mounts to the floor.
Pull the rod off the back of the pedal and make sure the pedal stay erect on its own and after you push it down, it comes back up.

The two springs, the one on the pedal and the one on the throttle body are the ones that pull the throttle body back to idle.
Both need to be clean and fully functioning. I forget who taught me about the pedal, but its truely part of the return system.

The additional spring, the safety spring or suplimental spring is for backup and it puts suchs a side load on the throttle body that it will highlight worn bushings and misaligned plates.


RIch

Well... started with what I thought was the easiest- the TB. Removed it and checked the spring everything seems to move very easily with the #4 spring off of the axle - pretty hard to move with the spring connected. The spring doesn't look like someone put an extra turn on it to make it stiffer (or if they did, it has permanently deformed to the new "setting").

Now for the new question: I took of the TPS cover to see what was going on in there. Luckily I was over my workbench so when the little rubber stop piece fell out (see orange box below), I caught it. Will super glue reattach the stop to the metal arm?

Click to view attachment

Still don't really understand what the #4 spring does. Have to play around with it some more after dinner .

yeah super glue, but clean both surfaces real well first.

OK - TPS "bumper" fixed. Back to the initial issue:

This is going to sound very backwards, but I think I may need a stronger "straight" spring between the top TB arm and the accelerator cable stop on the air manifold. From playing with the cleaned TB, if the top and bottom arms are 180 degrees apart (as if it were a '73 TB without the coil spring) the action seems easier. If the arms aren't 180 degrees apart, it seems like the throttle cable arm needs to be pulled harder (loading up the coil spring) until the arms are 180 degrees apart?!? This would account for the initial push of the pedal being hard... Can't test this until tomorrow PM (damn daylight savings time / winter).

Thoughts anyone?

initial pedal resistance goes back to the throttle plate getting stuck in my expereince.
there is a build up of invisible laquer that can occur...not sure it is laquer..there is just air going through it...
BUT
Dunk the throttle body in carb cleaner for a long period...it will get even smoother.
Cant see it, but the plate does stick a bit if there is a build up.
You can feel it on a taken apart TB...just the body, shaft and plate.
No springs, no TPS....
It should flop around, never getting stuck when you just shake it.
If not, sumpin is up.

Rich

It flops freely when it's down to just the flapper and the TPS - no sticking (had that problem with my Camry so that was the first thing I cleaned months ago).

Still have the feeling it needs a stronger top spring. The top spring should have enough strength to preload the coil spring #4 and then have enough left over to resist the pedal/ close the TB quickly. If the top spring breaks, the coil spring takes over and makes the pedal feel hard to push - letting the driver know something is up. Also, if the throttle cable breaks both/either spring will close the TB.

Again - hypothetical....

well, the supplemental spring does not always exist. It was not on two of my cars, it is on the 2.0 liter.
Without that spring, there is less resistance on the cable.
Have you checked the cable at the rear firewall?
It sometimes comes loose in the metal bolen end at the firewall and then it feel hard to push..till you push that back in and re-adjust the cable again.

Rich

Cleaned TB back in car and hooked up. The action is easier now so I guess disassembling and cleaning every nook and cranny of the TB helped.

I'm still going to change the throttle cable and play with the amount of force on the top spring - I want to make sure that when the TB flap is closed, the (2) TB axle arms are 180 degrees apart. That will have to wait until the weekend.

Oh, and of course the TPS adjustment is now out since I glued the little rubber stopper back in place.

Set it like the pic below when closed.
If you look close, you will see the idle circuit switch that only comes on when closed...that is your governor..it cant be set any other way.
Also, do check the cable where it goes into the firewall..they get cockeyed when you take all the pressure off to change something...they get loose and fall out of the bolen end that is fixed to the car.

Rich