RichLV's UrS4

[RichLV]

Problems again... This thing doesn't want to let me sleep...

These are the codes.


Pay attention only to the idle speed regulation. The premise is following:
1. Driving normally, car runs good, no issues on boost or low load.
2. Idle seems fine, but a bit high (around 900-950).
3. Then, CEL pops up. Idle does not change. But the car feels limpy when I lightly touch the throttle to accelerate, after a second or two, it comes back to normal. Transition to and off throttle seems rough and the car is "jolting" during it.
4. CEL disappears after shutting the car off and starting it again, but pops up after some time.

This is my idle


What could cause this? Dying ISV? Sticking throttle plate?


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[hunker7]

This thing doesn't want to let me sleep

Welcome to 20vt ownership.

[RichLV]

Welcome to 20vt ownership.

Probably feels lonely during the nights... *hope my gf doesn't read this*

[popdemonic]

My urs6 didn't have CEL from factory.

[popdemonic]

As a system, it functions well, now that I've played around it a little I understand the principles why it was made like that, but I'm surprised they didn't include somekind of a PCV filter element so that we could do just fine without catch cans, surely they knew that turbos feel better without oily fumes being thrown at them.

Next on the list - restoration of the rear suspension. I have a dissasembled rear sway bar assembly, which I'm gonna refurb with new bearings, abs sensors, poly bushes from Albert & control arms.

After that - 044.

If you searched the pcv here on this site.a lot of threads will show up
And alternative ways to eliminate the pcv.i have some oil surged out the pcv
too.i just have no time to handle this thing.with stock power level,the stock pcv
is doing fine but not with big turbo cars.the slosh effect will vomit the motor oil
out of the pcv.from my experience with high mileages car,if the valve guides are
worn out ,the excessive blow by will add on and making the situation even wosrse atleast
on my car.

[UrS4boy]

These are the codes.

What could cause this? Dying ISV? Sticking throttle plate?

The G28 code is likely because you pulled the codes with the engine off. The other two together and your symptoms, to me, indicate that you have an air leak somewhere. Strongly suggest that you do a full boost leak test, pressurizing at the the turbo discharge hose if not the turbo intake hose and using a soapy water spray bottle and 1 Bar pressure (constant until you find the leak).

AAN Boost leak testing:http://www.s2forum.com/forum/showthr...t+leak+testing

[RichLV]

My classic URS4

The G28 code is likely because you pulled the codes with the engine off. The other two together and your symptoms, to me, indicate that you have an air leak somewhere. Strongly suggest that you do a full boost leak test, pressurizing at the the turbo discharge hose if not the turbo intake hose and using a soapy water spray bottle and 1 Bar pressure (constant until you find the leak).



AAN Boost leak testing:http://www.s2forum.com/forum/showthr...t+leak+testing

The additive fault is long present in the list, it's because I have a leaky vacuum brake servo. When brake pedal gets pressed, in a specific position it starts to hiss and let through itself excess air into the manifold. But it only happens in a very specific pedal position, and was never throwing a CEL. The fault is there for a year or so. A new servo will solve it.

The idle fault is completely new and started a few days ago. I have nothing to pressure test, as all the hoses are completely new. The clamps are new, I went over everything at least 10 times, while I was at the rebuild process. I built it so that I don't have to worry about stuff like inaccessible (or hardly accessible) hoses. And when I was at the PCV remake (2 days ago), I went over the hoses again.

I realigned the throttle position sensor again today. Got it to drop the idle to 880 rpm. Will see if it throws a fault code again. Still a bit too high though.

Did a MAF test while I was at it, just to be sure. The readings do not differ from those I made last summer.


I'm gonna get another ISV tomorrow, see if will help (if I get the CEL after the realignment).

Also, remembered that the issue starts only when engine is hot. No CEL's while cold.

[UrS4boy]

MAF testing

Did a MAF test while I was at it, just to be sure. The readings do not differ from those I made last summer.

Sometimes when you are sure that something cannot possibly be the problem, after much effort to find another solution, it turns out that the "inconceivable" part is indeed the problem. That should sound familiar to you.

Based on the MAF testing worksheet that I created (and I think you used (except your printer has a phobia to "l" (ell): http://12v.org/urs/G70_MAF_TESTING_WORKSHEET.pdf , I think your's failed on a couple of issues (low voltages in two cases).

Here were my results from back when:

1. Testing for ground: Disconnect the harness connector from the MAF. Set your DMM to 20 ohms and look for continuity between Pin 1 (Pin 6 is the empty position) and ground on the engine or chassis. My result = 0.5 ohms = continuity = there is a ground for the MAF = good to go so far

2. Testing for connection to the injector circuit: Turn the DMM to 20 VDC. Connect to Pin 5 and ground. Turn on the ignition. You should get some positive DC volts. My result: 11.1 V = good

3. Checking MAF function: With harness connector removed, switch DMM to 200 ohms. Connect DMM probes to terminals 1 and 2 on the MAF (1 is on the right, 6 is on the left). Record the resistance. My result: 0.000 ohms
Disconnect leads and "Short" the circuit (press probe ends together). Display value must equal value recorded previously. My result: 0.000 ohms = same = good

If the difference is greater than 0.1 Ohm, replace MAF. (Nope. All is good so far)

Re-connect the MAF sensor harness connector. Peel back the rubber boot on the connector to expose the terminals. Switch the DMM to 20 VDC. Connect the DMM to the back side of Terminals 1 and 3. Turn the ignition switch to "ON" (run) but don't start the engine. Should be 1.2 to 1.5 Volts. My result: 1.25 V

Start the engine and let idle. Voltage reading should now be 2.5 volts. My result: 2.50 V

Increase the engine speed briefly (manually move the throttle position to more open). Voltage should increase to 3.0 to 5.0 volts (depending on engine speed). My result: 3.05 V

All the of the specified voltages must be obtained. If NO = replace MAF. (Nope, all good)

[RichLV]

My classic URS4

Yes, I remember the plugs... But this is different because I did check the air and vacuum lines, while the plugs went untouched until the very end...
For the record, today, I went over all hoses & connections with a carb cleaner (if theres a leak, then the idle starts to fluctuate) and with a leak finder spray. Nothing. The idle is rock solid at 880 and the leak spray did not bubble.

Yeah, well the MAF has been like that for over a year. Didn't experience any issues with it. I hope it stays alive for approx. one more year, after that I'm switching to speed-density. [emoji16]


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[UrS4boy]

Yeah, well the MAF has been like that for over a year. Didn't experience any issues with it.

If the MAF does not create the correct signal, the ECU will under/over fuel the cylinders and, unless the O2 sensor can give the needed feed back, to the ECU, you end up with a mixture adaptation issue.

Just sayin'

[RichLV]

My classic URS4

If the MAF does not create the correct signal, the ECU will under/over fuel the cylinders and, unless the O2 sensor can give the needed feed back, to the ECU, you end up with a mixture adaptation issue.



Just sayin'

Mixture adaptation was not present when I was still driving with hydraulic servo. And another MAF did not remove it after I changed it to vacuum. Tests done a while ago.

Also, if it shows incorrect signal, then it should under/overfuel the car on both idle and while driving/boost, hence I would be getting lambda control and multiplicative mixture adaptation faults. Yet I get only the idle one.

[URSIMPO]

Understood, thank you.

Intercooler? Read somewhere that stock one flows good enough for 500 or so HP. Or do I need bigger front mounted one?

http://www.kwe-racing.de/Audi/Audi-S...ml?language=en

This upgraded smic might be of benefit. Not sure what hp it's good for though. Certainley less of a faff than fitting an fmic.

[Kieron20V]

FWIW 38 Ohms is a $hitty ground. I wouldnt be ignoring that.

[RichLV]

FWIW 38 Ohms is a $hitty ground. I wouldnt be ignoring that.

What would be a good ground then?

***

Found the culprit. Damn brake servo... Removed it from the vacuum system connection altogether and the idle dropped to 760-800 rpm. Guess I need a new one then...

[Kieron20V]

as close to zero as possible. Really anything over 1 should be considered bad. 38 is a bad resistance.