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Sticky Gas Pedal...help?!?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sax Art, Jan 9, 2001.

  1. Sax Art

    Sax Art Registered Member

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    I've got a 1991 K5 that has a sticky gas pedal. It's not really sticky, but as you push down to accelerate, the pedal won't move, and then suddenly moves, so consequently the vehicle will then lunge forward.

    Does anybody know of a fix for this condition? I've tried the obvious WD-40 on the pedal pivot as well as both ends of the throttle cable and the throttle linkage under the hood. I'm hoping that this is a common problem that someone knows the fix for! Help!!!!!
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Try a new cable, I don't have anything scientific to back me up but sounds locigal.

    (Please direct all hate mail to "Blazer_Boy" because I don't think "BlazerBoy" would appreciate it [​IMG])
     
  3. northgate

    northgate Registered Member

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    Disconnect the cable at the throttle and see if it still sticks. If it does, it's the cable that's the culprit. If it doesn't, check your throttle linkage.
     
  4. Gandolf

    Gandolf 1/2 ton status

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    The gas pedal on my '89 is beginning to stick a little the way you described. Just today I was thinking about putting it in a post. I haven't even looked at it yet but if it's the cable, can it be greased or does it have to be replaced? If it can be greased, is Lithium Grease the best to use or is there something better?

    '89 K5 Silverado 4" lift w/BFG 33's
     
  5. Gandolf

    Gandolf 1/2 ton status

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    I thought I'd bring this question back since I did some exploring into the problem. I disconnected my cable at the TBI like northgate suggested and determined the throttle cable was not the problem. The problem is in the TBI unit itself. I think either the shaft that goes thru the TBI is binding, or the butterflys are sticking. (or both). With LPG #1, a dry lubricant, I sprayed each exterior side of the shaft bushings and also shot it towards the bushings from inside the venturis using the little red tube that attaches to the can. This improved the "sticking when coming off idle problem" about 75%, but I can still feel it sticking a little bit, and I sense the problem will slowly return. Does anyone know if this means the shaft bushings are wearing out? If so, can they be replaced or are they cast into the TBI housing? Or, are the butterflys somehow wearing into the TBI housing everytime I let off the gas? Or is it something else that I'm missing? (The truck has 148K miles on it).

    "You can’t have a real adventure, unless the outcome is truly uncertain".
     
  6. HarryH3

    HarryH3 1 ton status Author

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    Open the throttle plates and look down into the throat of the throttle body. Is carbon building up below the throttle plates? If so, a few shots with a good carb cleaner should clean it up.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  7. Sax Art

    Sax Art Registered Member

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    Gandlof-

    Thanks for your reply to my original post.

    I've got 141,000 miles on mine, so it sound like it's mileage related. You've already tried the cable. That rules that out!
    I've tried the pedal assembly. I took it all apart, cleaned off the old gunk, put new lithium grease back on the moving parts and put it all back together (it's quite a strange setup under there!) This made no difference! So this rules out the pedal assembly.

    Do you notice that it get's worse as the engine warms up? I've noticed a slight difference, that as it begins to warm up, it tightens from almost barely perceptable when it's cold, to damn anoying once it heats up! You're also correct that it's worse right off idle.
    If I'm stopped at a stoplight, when I go to start up again, it's really tough to get the vehicle rolling without a lurch at first! (but you already know about that!) I just about gave up on it, but because of your recent post, I'm gonna go home tonight and try to clean things up under the aircleaner. (Throttle body!) I guess it makes sense if it gets worse as it warms up that it would be something directly connected to the engine, and not the cable or pedal assembly.

    Good luck, and lets keep in touch so we can get this thing fixed!
     
  8. 89K5

    89K5 1/2 ton status

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    My 89 had exact problem. I put in a new cable and good as new. Took me about 20 minutes.
     
  9. Gandolf

    Gandolf 1/2 ton status

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    I'll pay attention to it tomorrow morning to see if it's worse after warmup. I did notice today that it is now an intermittent problem. Sometimes it sticks but most of the time it doesn't. The spray lube definitely helped. Sax Art, You might check your cable if you haven't already. At the TBI end of the cable is a simple clip that is easy to remove. (Be careful. It would be easy to drop and lose it. I'm going to buy a spare next time I'm at the dealer) My cable had no resistance at all when disconnected, but I could feel the sticking when I moved the throttle on the TBI with the cable disconnected. If I can't find the cause, I will replace the cable anyway, since 89K5 solved his that way. It's possible the cable could be binding under tension. Harry H3's had a good suggestion. With a flashlight, I will check for carbon buildup. That's a definite possibility. I'll spray some carb cleaner down there anyway...can't hurt anything to do so. After the carb cleaner evaporates, I'll hit it with the spray lube again. BTW, I used dry spray lube since an oily lube could collect dirt and dust. (Unless my K&N air filter gets 100% of it).
    I'll post the results tomorrow night.

    "You can’t have a real adventure, unless the outcome is truly uncertain".
     
  10. scavenger

    scavenger 1/2 ton status

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    I hope it is just a bad cable which would be an easy fix, however it sounds exactly like the problem I had last fall with the throttle body on our 89 Chevy Astro with the 4.3 motor. When you first started it when it was cold it would have a high idle and I had to step on the gas and release it quickly to get it to return to a more reasonable cold idle. I too replaced the cable with no improvement. At the same time I replaced the cable I noticed there was a lot of play in the throttle shaft. I then forced it all the way to the closed position and it took a lot of effort to open it. Once it was open a little it moved freely. I then noticed a wear mark inside the throttle body and found that the throttle shaft bushings were wore which allowed the butterfly to rub against the throttle body bore. I then tried locating a shop that would repair the bushings but struck out, and was told that they are non-repairable. About 3 weeks after buying a new throttle body a guy told me there is a place in Seattle Washington that will repair them for about $75.00. Don't know the name of this place but it may pay to search the web for it. Better than the $650.00 I had to shell out for the new one. If it is the throttle shaft bushings making the butterfly stick this is something you want to get taken care of for safety reasons......good luck.
     
  11. Sax Art

    Sax Art Registered Member

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    Update:

    Last night I pulled the air cleaner housing off of the throttle body. The first thing I did was pull the end of the throttle cable off (be careful with the little clip!). It seemed to opererate smoothly. I then took a can of WD-40 and shot a blast on the throttle plate shaft, both on the inside and on the outside where it goes through the body of the throttle body. I waited to test it until my commute to work this weekend because it seems as though it gets worse as the engine warms up. Sure enough, it didn't fix it entirely, but made it a heck of a lot better! I think I'm going to get some carb cleaner. I'll clean it up real good, and then get something drier to lubricate it with. I used a flashlight to look inside the throat of the throttle body with the throttle open. I didn't see any signs of bushing wear (loose throttle shaft) or binding throttle plates, or even carbon build up on the inside of the throttle body itself.

    I'll keep you all posted on the progress!
     
  12. jarheadk5

    jarheadk5 1/2 ton status

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    I can't tell you how many times I've forgotten to make this post!!! My 87 with 114K mi has the same problem. Cold it's not too bad, warm it gets worse. I'll have to try the carb cleaner/dry lube thing too...

    [​IMG] Semper Maintenance!
     
  13. Gandolf

    Gandolf 1/2 ton status

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    I didn't have time yesterday but I spent a little time with it tonight. I checked for carbon buildup but didn't see any. I could see all the way down and into the intake manifold. I sprayed a generous amount of Berryman B-12 Chemtool, a carb cleaner, down the throttle bores and re-lubed the shaft. I checked the shaft end play and although it does have some movement, I don't know what is allowable. I also dumped some Red Line fuel system cleaner in the tank for good measure. (I called a buddy who is a service manager at a Toyotta dealership and described the problem. He said to pour a product called BG44K in the tank. He said it's "very caustic" usually solves the problem. I can't locate any in my area so will have to get some thru his dealership. The problem is he's a 1 1/2 hour drive away). I may have seen some scuffing on the side of the bore where the throttle plates makes contact, but will have to look again to be sure. It was dark out, raining lightly, and I had a weak flashlight, so I only took a quick look and sprayed the Chemtool & Lube. Driving home it worked great until I stopped for gas. When I restarted it and began to drive out, it stuck again. This was the only time it did it. So, it's not solved yet but is way better than it was. I'll spend some more time on it this weekend. I'm thinking of pulling the TBI off and taking a real good look at it. Does anyone know the torque spec for the TBI? (I have an inch/pound torque wrench. I loaned out my ft/lb torque wrench and the guy moved out of town with it. He better stay outta sight if you know what I mean. Grrrrrrrr!!)

    Sax Art, no difference whether hot or cold.
    Scavenger, thanks for your input. I'm hoping mine isn't as bad as yours was.
    89K5, I may replace my cable this weekend. Even if I may have a more serious problem, with 148K on my truck, I'm sure my cable is worn and it's easy to replace.
    Thanks guys.

    "You can’t have a real adventure, unless the outcome is truly uncertain".
     
  14. Sax Art

    Sax Art Registered Member

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    Well, the update after 3-4 days of driving shows that the WD-40 on the throttle shaft seems to be working. There is still some resistance, but I would say it's about 75% better than it was. I'm guessing that the throttle shaft has worn itself at the throttle body/throttle shaft bushings and this WD-40 is only a temperary fix. I guess it's so quick and easy to do, if I have to pull the air cleaner and zap it with WD-40 once a month, thats not too bad. Like I said, it's not perfect, but it certainly makes driving much easier and less frustrating!

    Good luck!
     

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