BTW did you calibrate you throttle body recently?

 

Are you sure about that in a drive-by-cable car? I've tried 3 different MAF's now, all of them are known-good from cars that are running perfect, and they all show same readings on VCDS MBV. I think in the DBC setup the throttle position sensor must either built into the throttle body or it's on the firewall in the throttle cable housing...I don't know yet which.
So, I switched the throttle body for a known-good one, no change.
Also swapped the ECU from another car (same part# luckily).
Also, no change.
I've done the throttle body adaptation, (a couple times). No change.
And scratch that vacuum problem, it's holding vacuum fine.
I'm....stumped..

 

I have a DBC setup in the C4 and the TPS is "separate" from the TB - as in a purchasing part.
The same part is listed for 1999:
078133154
It looks like 1999 was the last year for DBC...
As I said, it's just a thought worth looking into since you said the condition happens only under throttle.
If all those different new TBs came with the TPS integrated, then please disregard my comments.

 

Does it do it TWO gears down from D?

 

Yes, it does it in all gears. And I've driven it with the TPS unhooked, still does it!
I drove it for 45 minutes yesterday w/ my laptop plugged in running logs.
I could not find a single reading out of spec in the engine or trans controller.
This is beyond me....

 

Are your exhausts plugged some how? How about try to run with your rear o2 sensors unplugged from the converters?

 

If it exhibits the same symptoms with it hooked, then it would make me think that's a part I would definitely want to replace.
You went to such great extent to replace so many other things, why not replacing the TPS as well?
You said that you put on a different "known-good" throttle body, but you didn't specify it was NEW.
If you bought it used off EBay and came with the TPS on it, then there are some chances that it may not be as good as you think it is.
If the ECU has no reading from it (so unhooking it leads you nowhere as far as determining if it is either good or bad), then there's no feedback loop existent otherwise with a proper functioning TPS. Hence the ECU can't adjust to "order" extra-fuel injection without a reading.
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Can you tell I'm stuck on the TPS? As stuck as you are on dismissing the possibility of it to be dead.

 

+Good point on the TPS, is the signal is bad then unhooking it doesn't help much unless the perameters are such that no-signal would cure the hesitation. I haven't been able to verify whether the TPS is on the throttle body or the throttle cable housing on the firewall.
The throttle body I swapped was from another car I had over the weekend. That car runs great, zero hesitation (it does have an oil leak though). And after the swap it still runs great with my old TB on it, and our car has the same hesitation. So I expect the throttle body isn't the problem, and therefore if the TPS is built into the throttle body as I theorize then the TPS is also not a problem. Also the TB adapatation runs Ok, and sets fine.
Same with the MAF, I've tried 3 or 4 different units (none new) from 1. used from Ebay and 2. Two other cars that run just great, and in VCDS the MBV readings are identical on all.
I don't assume ANY problem with the exhaust because typically if it was causing a low load/RPM hesitation it could only get WORSE at high RPM...right?
The car runs perfect at 1/3 throttle or more. And It flat screams at full throttle, not even a hiccup if you have a heavy foot.

 

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I know that there's a big chance I may sound like a nagging old woman.
With all due respect, may I ask how did you unhook the TPS if you don't exactly know where it is and you didn't have a chance to verify it?
You see what I mean?
Is there a chance that instead of the TPS you unhooked something else (probably the cruise control switch)?

That would make sense. If the exhaust/cats was/were clogged, then you'd have hard time to even idle it without problems and also the car would run much hotter than normal, with lots of power loss.

 

Pretty sure the TPS is built into the throttle body, and you can't drive with the throttle body disonnected, so the only thing I tests I can really perform are 1. MBV on throttle position which is OK and 2. Completely swap the TB with a good one., which I did.
I just don't have a name for the electrical connection that's built into the throttle cable on the firewall. Does anyone know what it is? 2 wires into a black connector. I assume it has something to do with throttle position, but disconnecting it does nothing, changes no values and has no effect.