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But Mad North-Northwest
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Discussion Starter #1 (Edited)
My 1991 Spider with the rod linkage has always had an annoyingly stiff throttle pedal, even after cleaning and lubing everything. I finally did something about it.

There are three springs on the linkage: one at the throttle plate, one at the crank beneath the throttle, and one on the crank arm across the firewall. The firewall crank one is really overly strong, so I replaced it with a weaker one.

The one I used is a CSC model C-143 that's carried in the parts section of a lot of hardware stores, but it's just a matter of trying some extension springs until you find something that works. It's loosened up the throttle quite a bit.

There are two other springs on the system so even if you leave this spring completely off (which I don't at all recommend) the throttle will still return properly. So it's not an insanely critical part, but that being said this is a modification to your stock throttle system. So do this only at your own risk.
 

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My guess is that 3 springs complied with a federal regulation.
 

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Gubi

My '91 also has rod linkage. I don't find the overall spring resistance to be high but at very low rpm with the clutch disengaged such as crawling along in stop and go traffic, it definitely is herky-jerky when trying to accelerate slightly from a coast. I've gotten into the habit of slipping the clutch for a second at the point of begining to accelerate just to avoid it.

Did your spring replacement help at very low rpm?
 

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But Mad North-Northwest
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Discussion Starter #4
Hard for me to say. I've had the car so long I've gotten used to its foibles. It definitely feels a lot more like the cable throttle on my Milano now, though.

Problems with the rod linkage at the point of actuation are usually either something needing lubing in the linkage, or very often slop in the bushing in the firewall crank arm.

If you look on the passenger side of the crank arm across the firewall, there's a pin that connects the arm to the next rod in the linkage. This pin sits in a rubber bushing. If the bushing is shot and the pin is flopping around, that can be the source of a lot of weird feel when actuating the throttle.
 

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But Mad North-Northwest
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Discussion Starter #6
Those were fine. Like I said, I'd already gone through the whole thing looking for any binding. The crank arm rotated smoothly.
 

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I did basically the same thing to my 88 Grad shortly after I purchased it.

However, I'm way too cheap to buy a new spring :whistling: so I took the OEM spring and stretched one coil to the point of permanent deformation.

It worked like a charm and I've never looked back
 

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I don't find the overall spring resistance to be high but at very low rpm with the clutch disengaged such as crawling along in stop and go traffic, it definitely is herky-jerky when trying to accelerate slightly from a coast.
I have noticed the same thing. I can't press it smooth enough at very low speeds or stop/go traffic. It's like I am overcoming some kind of sticking point. But then it's to far pressed and it's more than I need. Then you slightly let off and overcompensate the other way. Herky-jerky is right.

When I put my plenum back on, I put grease in the 3 linkage ball caps. When my son would press the peddle down to test, I heard some creaking/squeaking sounds from under the car on the drivers side. Maybe on mine it just needs some lubricating.

Looking forward to what others came up with.
 

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But Mad North-Northwest
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Discussion Starter #9
If you pop off the two rods, you can actuate the throttle, crank under the throttle, and firewall crank arm separately to find any issues. A common problem is that the crank under the throttle can start to seize up. Also see what I said above about the bushing in the firewall crank arm.

In my case all this stuff was fine, it's just that that one spring is way stronger than it needs to be.
 

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I have noticed the same thing. I can't press it smooth enough at very low speeds or stop/go traffic. It's like I am overcoming some kind of sticking point. But then it's to far pressed and it's more than I need. Then you slightly let off and overcompensate the other way. Herky-jerky is right.

When I put my plenum back on, I put grease in the 3 linkage ball caps. When my son would press the peddle down to test, I heard some creaking/squeaking sounds from under the car on the drivers side. Maybe on mine it just needs some lubricating.

Looking forward to what others came up with.
Gary,

An odd coincidence that you should mention the creaking/squeaking. My '91 has been doing the same thing. I can't imagine it's related to our common throttle issue, though—more likely just a noisy suspension bushing that in my case is mostly obvious when I take 200 lbs off the load when I get out of the car.

After Mike mentioned the throttle shaft bushings, I took a light to the firewall and checked mine out. The rubber looked fine so I just hit both with a spray of Tri-Flow lubricant and worked the throttle back and forth. Took the car out for a spin and the low speed jerking was definitely better.

This Tri-Flow Lube has been an inexpensive miracle fix for a number of problems on my Alfa [read here: http://www.alfabb.com/bb/forums/spider-1966-up/321017-stuck-ignition-switch.html]. Can't say enough about the stuff.
 

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I don't know about you guys but the "herky jerky" at low speeds or traffic crawl is something I've experienced in every manual shift car I've ever owned. MG's, Jag's, Triumphs, Alfa's, VW's and even a newer stick shift Honda. Whether they had all rod linkage or cable or combo, they all did it to some degree. Slipping the clutch to smooth this out was the best I figure out.
 

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But Mad North-Northwest
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Discussion Starter #12
The problem with TriFlow is I think it's oil based and thus *might* cause the rubber bushings to break down over time. Spray silicone might be a better option for that particular application.
 

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I had this problem a LOOOONG time ago on my then-new 67 Duetto.

The bushings at the firewall were one of the problems, but the major one was the pivot on the bell crank lever under the carbs. I guess due to engine vibration, this loose fitting steel-tube bushing on a steel shaft wore so much that the bell crank was loose. I drilled it out and pressed in a bronze bushing, turned the bell crank shaft smooth and round, then bored the bronze bushing to fit properly. It's been over 30 years and I've had no problems since.

Robert
 

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But Mad North-Northwest
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Discussion Starter #15
I drove this a bunch more today and I'm really happy with the mod. Between the three springs there's still plenty of force to shut the throttle plate, but the feel is much improved. For years I'd wished my car had the later S4 cable throttle linkage, but this mod has made the rod linkage feel like the later cars.

As to the throttle rod ends, specifically the vertical coming off the bell-crank, plastic ends seem to be a better choice than the metal
The metal links work fine so long as you put some grease in the cups. Plus they won't crack and leave you stranded like the plastic ones have been known to do.
 

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glad the metal links work for you. my experience is different. the metal links being sold currently are not like the old style that had an external keeper, the current internal snap ring is not a good fit for the vertical rod that moves in three axis. I imagine AR choose the plastic ends for that reason.
 
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