TBI throttle sticking

[awestbrook]

Hello All!

I wanted to get some ideas about a sticking throttle from the community here. I have a 91 K1500 w/Vortec head, GMPP EGR intake which was bored to match the bored TBI from RV Morse (RIP). Also, comp cam (I forget which one, but middle of the road so to speak) and Dynamic EFI computer.

The throttle only sticks with the engine running, which to me implies that the shaft or bearing is worn, but I feel no up/down play and very little side to side. I've had this issue from the very beginning of the build, and also sent the TB back to Morse for inspection, which he said passed.

The TB slams shut when worked by hand when engine is not running. Likewise, the throttle cable (new) is very smooth with little felt drag when operated by hand.

What is also odd, is that there are long stretches where it works absolutely fine, only to slowly degrade to near un drivability and back again.

I'm happy to post pics or videos.

Suggestions Welcome!

thank you!

[PlayingWithTBI]

I had an issue where, if I set my min idle screw too low, the throttle cable would jam in the sleeve which covers it at the TB. Another possibility is the throttle blades are closing too far and, with the engine vacuum, getting stuck against the bore. Check your IAC step counts at idle and see if you can increase the min idle screw a little without getting your IAC counts too low, you want at least 10 counts. HTH

[tayto]

above is good advice. you may also need to reindex the throttle plates. when i rebush them i actually hold my ear up to them as i open the throttle and listen for contact.

[awestbrook]

Hey PWT! It's been a while. Hope you are doing well. I'll send you an email separately after a bit. A LOT has happened LOL.

So, yeah, step count seemed high, 70 at idle. I hadn't paid attention to that in a while because it seems to idle just fine at 700. It took 2 full turns of the throttle stop screw to get the counts down to the 15 level. I should probably do a complete reset of the IAC system, but I couldn't quickly find the instructions. I'll have to dig around for those.

The bummer is, it didn't completely fix the issue. It seems there is just enough drag on the throttle cable to hang up the TBI if you go to maybe 5% on the TPS and then let off. So maybe I'll try to lube it and the pedal pivot joint and see what happens next.

[PlayingWithTBI]

Hey PWT! It's been a while. Hope you are doing well. I'll send you an email separately after a bit. A LOT has happened LOL.

Sounds good! :thumbsup:

[PlayingWithTBI]

I should probably do a complete reset of the IAC system, but I couldn't quickly find the instructions. I'll have to dig around for those.

Try this...

[tayto]

you dont need to do the reset procedure (known as base idle) if you are setting by IAC counts. i take on a Good drive to make sure engine is heat soaked, set between 10-15 counts, turn off vehicle for 10 seconds theb restart and confirm it is within the range.

[awestbrook]

you dont need to do the reset procedure (known as base idle) if you are setting by IAC counts. i take on a Good drive to make sure engine is heat soaked, set between 10-15 counts, turn off vehicle for 10 seconds theb restart and confirm it is within the range.

My son took the truck to school today and mentioned that the counts seemed to give erratic results at times, dropping to zero a time or two. I'll try again this weekend under a little more controlled setting and see what I get.

I'm curious what route your throttle cable takes under the hood. We have ours make a loop as it comes out of the firewall and onto the bracket.

[PlayingWithTBI]

I'm curious what route your throttle cable takes under the hood. We have ours make a loop as it comes out of the firewall and onto the bracket.

Mine's more like an "S". IDK if I have enough to make a loop.

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