So before I start, I did searched. I got 2 questions:

1st, does double throttle diaphragm supposed to hold vacuum when testing with pump? or does it vent somehow?

2nd, When testing tps for ohms with connector disconnected, is TPS supposed to be installed in TB, or do you test with it being off the car completely?

My car: 89 GTU 5 speed.

Symptoms/Test result: Car warms up great, AWS and thermowax seems like theyre working. Once it warms up, than idle jumps from 500-1100 rpm, and eventually stalls. Ignition timing, idle top screw and tps all have been adjusted, (tps adjusted with 2 LED connector), bac have been checked, cleaned and lubed. I have checked my tps today on the tb. From A-B closed: 2.something k ohms and from D and the other pin is off too.

I want to try and soak it in electrical cleaner and see if it will fix it?

 

The vacuum hose to the diaphragm has vacuum until the engine warms up and then there is no vacuum.

The TPS is supposed to be connected to the throttle body when adjusting it and the engine is to be warmed up completely and that usually takes a 20 minute drive to do. And you can set the TPS using the voltage method and w/key to on the Green/Red wire would read close to 1 volt w/key to on.

 

I understand about vacuum being there until it warms up, but does diaphragm it self supposed to hold vacuum when testing with pump?

And is it that important to warm up the engine to check tps resistance (unplugged)? Not adjustment, Im talking the sweep, closed and WOT

 

Yes, extremely, and you get much better results setting by voltage than by ohms

 

[QUOTE=s70simon;12000074]I understand about vacuum being there until it warms up, but does diaphragm it self supposed to hold vacuum when testing with pump?[quote]

yes. if it doesn't replace, you could just block it off.

yes. the thermowax pushes the throttle open, so when the car is cold the throttle is not closed, ergo you cannot adjust the tps. also for whatever reason the TPS moves around a little bit, and its better to adjust it when everything is HOT than it is, just warmed up

 

The diaphragm should hold vacuum but after aging they tend not to. When the diaphragm fails the spring linkage holds the throttle plates open (not closed) which is good.

The sweep of the TPS should be from idle position to wot so the TPS would not be in true idle position if the engine was cold.

 

corrected to avoid confusion.

unless you live and drive in sub zero temperatures the double throttle is rarely used and can be left in an idle state. i tend not to say "removed" because i've seen plenty of hacked throttle bodies. most people won't notice any additional benefit of removing them completely.

 

So here is the update:

First thing I did is put a cap on a thermo switch (for the double throttle diaphragm)

Next I warmed up the car a little, went for a 15 min "spirited" drive. Came home and adjusted the sensor by voltage with green/red wire, to 1 volt at idle. Made sure the sweep had even volt increase, which went to about 5 something volts. Unplugged tps connector and checked ohms resistance, got A-B 1.5k ohms @ rest, and 6.6k @ WOT. D-E 1.4k ohms @ rest, and 7.7K @ WOT That is off based on the FSM. Car idles steady around 1,000 RPM.

Tried adjusting idle. Grounded green check connector. First got my secondary plates adjusted by backing the screw off, then screw in until it barely touched and idle changed slightly. Tried adjusting top idle screw, went all the way in and its still at 1,000 RPM. Checked ignition timing again, good. Went for another drive, exhaust has a small backfire during deceleration in gear. (I do have a corksport 3" catback, with stock mani and cat)

Even though it idles smooth now, Im not satisfied with the results. I want to get idle rpm to at least 800. Also backfire doesnt seem right. Im thinking tps is off.

 

On an S5 the G/R wire reading of the TPS can range from .75 to 1.25 volts as stated in the FSM so you have a little to play with.

 

i think your DVOM is probably cheap or not very accurate, those numbers are out of spec.

 

Dont think so, I had it for over 4 years now and payed $200 for it new. If the numbers are out of spec, it cant be that sensor is what out of spec? Is there another adjusting procedure I should follow? Can anyone point me to a complete throttle body adjustment, including primary and secondary plates? (p.s. wax pellet (cold start screw) and primary plate gap have been adjusted to the best of my ability based on FSM)

 

When adjusting the TPS did you ground the Initial Set coupler?

It would be well worth the effort to remove the throttle body and go through the thermowax adjustment when you can actually see what you're doing.
It is critical that when the car is fully warm (which you can easily simulate by pouring boiling water into the thermowax) that the linkage allows the throttle plates to drop fully onto the static adjustment screw. The initial/static adjustment is made with a feeler gauge and determines the base level idle, you fine tune with the air bleed screw on the top of the body.

You must confirm that when the thermowax is hot, the throttle plates have closed to the factory spec gap.
Every thermowax that I've removed has been full of silt/crud, which can't be good for them...the system is kind of crude to begin with and completely dependent on good waterflow, so it needs all the help you can give it.

 

Not sure which plates you are talking about here.

Is there a procedure for that?

I had the TB removed and cleaned with carb cleaner and compressed air. I checked to make sure thermowax opened with heat gun. Also I have set fast idle with TB off the car.

For the primary plate I got it to where there was about .5 mm gap between the bore wall and plate. And got secondaries to where they are just barely resting on the "stop/adjusting" screw.

 

Honestly Im at the point where I want to just find a used TB that hasnt been messed with and try that on. Clean it and adjust tps and top idle screw with out messing with fast idle or primary/secondary plates. If anyone can find a COMPLETE throttle body adjustment, including plates, that would be awesome.

 

it's all outlined in the FSM

i limit the TPS to about 5.5k before the resistance is too high

 

Another update: Today I got a check engine light with code 17, Feedback System. Going to order a new o2 sensor and try to check for vacuum leaks.

Also ordered another TB that was supposedly not messed with. Going to install it next week.

 

Any updates?

So how is this new throttle body for you
Your were speaking about backfire , did you adjust the timing before the TPS ?

I had good success decrease backfiring doing it
on different cars.