Sorry to crosspost but I'm getting zero response on the Holley forums :-(

Had another go at it and went to check my throttle position sensor settings. Instead of measuring the current (.58V @ idle position), I simply connected my laptop and opened the data monitor page. According to the manual:

Instead of 29-31 at closed throttle I got 41, aha! However, even with the TPS adjusted all the way, I couldn't get it below 38. Unscrewing the idle screw on the throttle shaft itself brought it down to 35, but that's it.



So I took the TPS out completely and it actually read 1, which seems to indicate it's working just fine. The problem seems to be with the throttle shaft itself or with the little pickup lever which moves the TPS:



As you can see even at closed throttle position it's not at rest (as in all the way to right). It's almost at 12 'o clock, and there's no way I can adjust the TPS that far.



I tried to unscrew the pickup lever, but it wouldn't budge and I didn't want to damage the throttle shaft by using force. Of course there's also a screw holding on the corresponding lever on the TPS, but I didn't touch that just yet. There has to be a way to do this, please!

Those TPS sensors have a rep for getting "dirty" at the idle position. With it hooked up and you monitoring the data, slowly open and close the sensor, it should sweep smoothly with no jumping around of the data.

Also verify that the throttle is not being mechanically held open by something preventing it from returning to idle.

Hmm you could have a point. The engine does idle at around 800-900 RPM but I can't close the throttle blades any further than they are now, no travel left in the throttle cable.
Sorry for asking but do you close the throttle blades completely like do they have to be 100% flush with the intake manifold: |_|?

2 things then.
1 disconnect the throttle cable.
can it close further now?

2nd, most software allows the system to learn the throttle settings instead of saying 1 or 41. is there a calibration screen?

1) I'll try that. It's been a few years and I didn't install it myself but I seem to remember that I had to order a throttle extension lever. The manual does indeed mention HLY 20-14 or -7, depending on the application (passenger car/truck). Again: I'll check that.

2) It does have a calibration screen and I tried that. Didn't do much though. Updated my throttle angle to 45-215 (closed/WOT) but it didn't seem to do the trick. I think you can't recalibrate for an out of spec throttle position (if that makes any sense).

no idea what it looks like, but for MS and painless it wasn't a number you could put in.
it had you tell it when you held down the throttle and then told you to let go.
it had you do it a couple of times to learn the throttle range.
but maybe holley's isn't like that.

Ok, checked the throttle cable. It does use the correct HLY 20-7 (https://www.summitracing.com/int/parts/hly-20-7/media/instructions) adapter btw:



Unhooked the cable but no: the throttle won't close any further. So not a mechanical problem at least not related to the throttle cable etc.

Checked the little pickup lever on the other side which does unscrew:



Nothing to adjust there either. It's held against a rounded rectangle by the screw so there's only one way it can be fitted (apart from flipping it over and installing it 180 DEG out).

That seems to bring me back to the throttle position sensor. If I can't adjust it to read 30 DEG with the throttle closed (as per specs) this would suggest I'll probably have to replace it.

It's the same with mine, you don't put the numbers in yourself. Sorry for being unclear. Press and release the accelerator pedal (only once though), save and send updated settings to the ECU.
Since they make it a point that you absolutely have to adjust the TPS to 29-31 DEG throttle angle during installation would however suggest that you can't redefine "zero" in software. AFAIK that's only to determine the amount of travel between closed and WOT position.

So let me make sure I understand the problem.

With the tps mounted it reads 41 as low as 35 with everything backed out.
It must read below 31 for this to work. you really need it at 38 with idle setup.

with the tps removed you can get all the way down to 1. So the sensor isn't broken. (so no reason to replace it).

I am assuming you read the section it references. It also looks like the sensor has slotted holes to let it slide around, I am guessing for the adjustment.

now I would say it is odd and unlikely that holley had this issue for everyone. but I wouldn't put it past them.

Since that lever seems to be a replacible part, I would probably grind off part of it till I hit the amount they wanted. or bend it depending on how much actual movement is required to get your amount.

OR perhaps open up the slots a bit more for more movement?

But double check the sensor. Have it off the car and attempted full range of motion. See what the calibration sees there. If there are any gaps or issues with it from the software side.

Well, someone pointed out to me that my MAP readings were far too high and he's right. Instead of having it connected to manifold vacuum I had everything on timed vacuum. At least that's easy enough to correct. Bought new vacuum lines and hooked everything up correctly this time: manifold vacuum to MAP sensor, timed to distributor. Didn't change the timing or anything else.
Still no way to adjust the TPS* below 40 DEG but thought I'd give it a try anyway.

Seemed unwilling to start at first, slightly lumpy idle afterwards. Had to give it more gas to keep the engine running. When it eventually died it gave of a large fireball! Had to jump out of the car, rip my shirt off and put the flames out, damn!
What's that all about?



*new TPS on the way but that's going to take until next month. Cost me 90 bucks including shipping and import taxes too. :-(

Well, my replacement throttle position sensor arrived and you're right:



Slightly odd way to fail but apparently the old sensor didn't properly return to idle.
I'll check the MAP sensor with a Mightyvac next, just in case.

Yeah, the Holley Projection setup was based on the GM TBI system with Holley's controller. MOst, if not all, the parts are GM based.