As the title inquires, has anyone had a TPS cause a poor idle despite the fact that the wiring harness from DME connector to the TPS connector has 0.2 ohms or less on each wire, the TPS potentiometer sweeps without a noticeable break (using a blue-point dmm) and within the correct resistance range, and the idle switch test fine? If so, any explanations for how this is possible?

Once off the idle contact the car runs like a champ with good air to fuel ratios (steady), although on the idle contact the car runs slightly lean approx. 15.3-15.9 (not steady). This unsteady idle mixture is causing the coolant temp to be slightly higher at idle if idling for an extended period (but will never overheat or go past 100 degrees celsius - last white line). Slight idle misfire but not misfiring off idle? Or just not noticeable?

The car is making the amount of rwhp is should be with the mods it has along with the fact that the air to fuel ratios are steady (approx. 11.6-11.7 under WOT), so I have always assumed that the misfiring is only at idle.

Sorry for the second post so quickly. I have been trying to track down the cause of my poor idle for over a year (when I have the free time outside of the shop to work on my own car). I would approach this differently, although the number of possible components to test on this car are running out. Please feel free to post any suggestions.

Car has a new ISV (was leaking vac.), no vac leaks, wiring harness with all wires 0.2 ohms or less, vitesse maf, siemens 55lb injectors, promotion turbo, lightened crank and flywheel, 3" exhaust, adjustable fpr set at 3 bar, new dme temp sensor..not sure what else to list. I can not find a faulty component and even with no vac leaks i have pinched off and isolated as much as the vac system as i can to try to isolate a problem with no success!!!

 

Explain what you're seeing as poor idle. Yes that is a bit lean, is it like that all the time at idle?

Take a look at this thread...
https://rennlist.com/forums/924-931-944-951-968-forum/404414-weird-idle-stumble.html

 

I had a poor idle caused by a failing Fuel Pressure Regulator... although it was running way too rich and not lean. Just something to test out :-)

 

My idle does not stumble as described in that thread.

 

Suggestions on testing this? I would guess test it to see if it holds vacuum. I know when I set fuel pressure (this problem existed then) the fuel pressure was reading a steady 3 bar with no fluctuation, however I do forget whether or not this was with or without vacuum applied to the regulator.

 

Is it possible the set of chips you have for the car is not mapped correctly?

 

I guess I don't doubt Vitesse and have not yet. We have discussed the idea of my injectors running poorly at a low duty cycle (@ idle), however even with an increase in duty cycle at idle the car does not have maintain steady air to fuel ratios (will richen the air to fuel ratio but not cause it to run any better).

 

If it helps my car has new injectors (siemans 55 with chips), fuel pressure regulator, and throttle position switch and my afr at idle seems to change with engine temps. Sometimes it idles in the 14s and sometimes even 10s.

 

idle air control valve?

 

I would start looking for problems.