73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Gusgusa1 on August 21, 2015, 11:20:45 pm
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I need help. I have a 1987 gmc with 350 tbi. Throttle cable broke and I replaced it. Problem is its a couple millimetres short so it revs the engine hard core. Can I adjust the cable at all? Or should I mess with the throttle position sensor?
Options? Please.
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Pioneer CA-8314 (http://www.autozone.com/fuel-delivery/accelerator-cable/pioneer-accelerator-cable/41999_0_0/) is 28.8" long and fits all '87-91 R/V trucks with TBI. What did you install?
Does it idle down properly if you disconnect the cable?
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Yes, I got it online. Do I just give the bracket an ever so slight bent forward or do I mess with tps?
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Only One more thing to break before it goes to a pro
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Do not alter the TPS adjustment as it will not help the symptoms, but will introduce other problems!
If you unhook the cable from the accelerator pedal under the dash, will the cable extend far enough to let the engine idle properly?
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Yes.
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Get a helper and a flashlight. With the cable reattached under the dash and the accelerator pedal pressed to full throttle, does the TBI throttle plate open all the way to vertical?
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Grabbed a crescent wrench and bent the bracket also took a drill bit that was ever so slightly larger than the hole and shaved a hair out of the hole.
The issue was the geometry. Since the cable wasn't straight with the connector between the bracket cable and linkage it bowed out in an arc toward the drivers fender. With some tweaking it is now better but not perfect. The cables are over 60$ in canada so I was understandably miffed that it didn't fit.
It moves the range it should and is smooth.
Thank you for the help :)
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...The issue was the geometry. Since the cable wasn't straight with the connector between the bracket cable and linkage it bowed out in an arc toward the drivers fender. With some tweaking it is now better but not perfect.... Thank you for the help :)
You're welcome.
So there was more to the story than just a replacement cable that didn't fit.... Any idea why there is a geometry/alignment problem? Is it modified from the original factory configuration?
If it makes you feel any better, I had to fabricate custom adjustable brackets for cruise transducer, TV cable and throttle cable when I converted my 87 to MPFI. Achieving the correct angles, offset and extension was time consuming.
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I don't know all that's been done to it. But this is what I gather
- light wieght pistons
- headers
- H pipe exhaust
- throttle body spacer
- 400 crank
- hyper tech program
- throttle body is modded
- LSD front and back
- some kind of cam
- 12 second truck
I got it from a widow whose husband passed last winter, so the secrets passed with him.
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It has always been a stiff throttle at the start. No easing off the line lol. Trying to figure that out.
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Throttle moves free at the tbi and peddle moves free when cable unhooked any idea why I almost have to stand on it to begin depressing the cable?
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The throttle cable should be long enough to make a gentle loop in the engine bay, this allows for flexing as the engine moves and prevents binding. If your cable is a straight run from the firewall to the cable bracket, it is way to short and probably binding up
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Timthescarrd states a valid point. Still, from what you posted previously, this has been a longstanding problem that preexisted your recent replacement of the throttle cable using a cable cataloged for your specific application. Posting some pics might clarify what you are running into.
What did you mean by, "the throttle body is modded?" Are you relying on the stock TBI throttle return spring incorporated with the base or has an external spring been added? Is the cable aligned 90° to the throttle shaft and parallel with the valve cover? Perhaps the cable entry angle to the throttle lever arm is too severe. Is the TPS sticking. Are all the throttle levers secure? Does it have cruise control?
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x2, if you have any kinks or sharp bends, you'll have a lot of trouble with stiffness and sticking.
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Modded simply means the bowls have been ground down. Every thing mentioned is good. Except the angle is not 90 degrees to throttle shaft. I think the spacer in part threw that off. I will look at shimming the bracket tomorrow. I think the plastic sheaves are binding at closed throttle and making for the hard push. Does this sound like a possibility? I will see if I can get a pic up. But always says my files are too large.
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How to upload pics to the forum from you PC (http://forum.73-87chevytrucks.com/smforum/index.php?topic=6428.0)
or use Photobucket and use the img code or you can use their app
(http://i333.photobucket.com/albums/m387/rebel_cowboy_83/stuff/imgcode_zps0a45dac2.png)
but he prob had a throttle cable off something else
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Possibly. In the spring I will remove he bracket and see if I can straighten out the geometry the line sways out towards drivers fender due to how the plastic retainer sits in the bracket. This creates uneven resistance in the sleeve. Needing it to jump a tiny amount to begin the sliding action between the plastic parts. It creates an outward force pulling the throttle at the tb outward slightly rather than straight back.
I am not mechanically inclined or a fabricator but should be able to shim or something to relieve the inappropriate forces.