Symptoms of a cheap throttle body -- and recommendations for something better?

[Alvin]

Got some new info:

1. I evaluated the setup as-is. By actuating the throttle by hand (at the throttle-body end of the cable), it opens such that the blade is fully parallel to airflow.
2. However, by actuating it via the pedal, it only opens to about half that! (This is where I saw 2.25v) :facepalm:
3. Back to actuating it by hand and watching the TPS % in Scanner, I saw 0.14% -> 100%. That explains why it won't idle!
4. Did a TPS relearn. Now I see 0.4% -> 100%! Success!

My kids are asleep and the garage is directly below their bedrooms, so I couldn't start it up and see if it will idle now. I'm somewhat optimistic, but prepared to have to mess with IAC and possibly do some drilling before it's totally happy.

I checked the pedal box, and there is nothing interfering with the pedal travel, so now I just need to figure out how to adjust the pedal/cable. I know of a couple spots along the cable where you can make adjustments, but those are maxed out. If anyone knows the LS1 F-body setup well enough to give advice, I'd appreciate it -- but I'll go ask on LS1Tech, as this is not really a tuning question.

One followup question: the voltages I saw from the TPS ranged from 0.14v (0%) to 3.92v (100%). Should I be concerned that I'm not seeing something closer to 5.0v? If so, what might I do about it?

Ed has already mentioned this.. There are two different belcranks used on those early throttle bodies. It sounds like you have yours in the wrong hole or that the throttle body has the wrong bell crank to begin with.

[edcmat-l1]

Or, with an aftermarket T-body, the cable isn't in the proper hole in the arm and the blade actually isn't opening all the way. Very common and easily overlooked by DIY guys.

2. However, by actuating it via the pedal, it only opens to about half that! (This is where I saw 2.25v) :facepalm:

Boom.

I saw from the TPS ranged from 0.14v (0%) to 3.92v (100%). Should I be concerned that I'm not seeing something closer to 5.0v? If so, what might I do about it?

The range is definitely off. Holes probably need redrilled so you can clock it. That will set a TPS low error code. Needs to be .5ish volts at idle.

[JakeRobb]

See the cruise control module on the passenger fender well? I opened it up and put a cotter pin through the holes in the cams to lock them in sync. Unplugged the module. There's probably a better way, but I didn't bother with it because I never use cruise control.

I'm a heavy cruise control user, so that option wouldn't fly with me.

That said, I figured it out. Turns out I'm an idiot; user error. Details here: https://ls1tech.com/forums/generatio...nt-issues.html

[JakeRobb]

The range is definitely off. Holes probably need redrilled so you can clock it. That will set a TPS low error code. Needs to be .5ish volts at idle.

Oh, I can just rotate the sensor within its mount and drill new holes to hold it in place? Cool. I imagine this sort of issue is less common with more expensive TBs?

So, a ~4v range from closed to open is normal, but I should I clock it so that it reads ~0.5 -> 4.5? I assume I'd need to do another TPS relearn after that.

EDIT: found this thread on LS1Tech which says I should shoot for 0.6-4.6, but also says that as long as we don't drop below 0.2, the code won't set. I'm barely outside the acceptable range.

[SiriusC1024]

Haha at least you figured it out. Progress Elongating the holes in the TPS is to get correct closed throttle voltage. You'll need another TPS learn. Later on you may find that further adjustments will have to be made as you set the throttle stop. The link I gave you at Post #2 will tell you all you need to know about it.