Please help with a weird problem

[KFXGUY]

Ok fellas, I have a very weird issue. It?s making me want to pull my hair out. 2004 ls1 gto. Cable driven throttle body. The throttle body is a ebay 92mm. Before you say it?s the throttle body (and it very well may be) hear me out. I have this anomaly, I can?t purposely make it happen, it?s random. I can watch my scanner at idle and every now and then my tps % will go from 0 to .4%. It?ll happen when I?m coming to a stop and it?ll cause the idle to dip, surge etc. I?ve also had it just get stuck st .4%. No matter if I open the throttle and slam it shut, it stays there. Only think I can do at that point is a tps relearn. It mainly will do that if I rev the car in neutral and if it dies returning to idle it?ll get stuck at .4%. I?ve replaced the tps three times. The first two were borg Warner (junk) and the one I have now is a new delco factory one.

I found (before I put the delco one in) that the throttle shaft part that goes into the tps was too long and the flat part wasn?t far enough in the recess. I chucked the shaft up in my lathe and made the dimensions match a factory throttle body. Didn?t help. It was binding in the previous tps?s i Had but not the one that?s on there now but I still have the same problem. I hat to go spend $400 on a new nick Williams Tb and it not fix my issue. A buddy of mine told me sometimes the .4%-0% are so close that he shims the throttle blade open a tiny bit and then does a tps relearn so you have a little more leeway in the 0 position. Makes sense but seems like a rigged up way of doing it. Maybe there?s a setting I can?t find that allows me to raise the minimum idle %? Has anyone seen this weird issue?

[dermotw]

Mine is just the same, however it makes no difference so long as you have the ECU parameters set so that anything under e.g. .6 is seen as 'closed'. At least thats been my experience! ('99 TA ECU...) An OE TPS does help a bit compared to the chinese ones they come with, lol.

-D

[KFXGUY]

Mine is just the same, however it makes no difference so long as you have the ECU parameters set so that anything under e.g. .6 is seen as 'closed'. At least thats been my experience! ('99 TA ECU...) An OE TPS does help a bit compared to the chinese ones they come with, lol.

-D

How do I do that? I haven’t found a parameter that does that yet.

[dermotw]

Err, several... don'k know if I could list them all, and they likely vary by ECU type, but they all affect how/when it drops to idle in various ways, e.g.;

Spark >> Advance >> "Tumble flap closed" (its the wrong name..) >> Min TPS
Fuel >> Open & Closed Loop >> LFTP idle cell threshold >> disable TPS and on same page Proportional idle threshhold >> idle TPS thresh
The TPS step size on the idle >> airflow >> throttle follower maybe if its less than 1% (unlikely imho).

Probably mainly the first one: if it doesn't 'see' the throttle as under that, it wouldn't use the idle throttle table(s), it'll use the main one. Mine is on .9, I <think> the default was .4 The hysteresis applies only on OPENING...

Dying on return to idle is a pretty common thing that people have a hard time getting rid of anyway, also dying at odd moments when manoeuvering for example (full lock, swing into parking place... etc.).

kr D.