forum.audiv8.com Foren English Audi V8 Forum A drowning V8 with a G40 error (motronic problem)

Help!!! After 2 months of searching I can still not find the error in my dear V8s engine steering system (motronic). I had even been pushed so hard, that I tried to send the car to an authorized Audi dealer for repair. And for me it is a big time humiliation, to admit that there is a problem I can’t crack, but never the les – this is the case.

BUT!! I just got the car back from the Audi dealer. In Denmark Audi take €120 an hour, and this is plain robbery in broad daylight. At the same time they didn’t find anything the first 8 hours they used, so I stopped the gambling and took the car home again. The problem is also that there is only aprox. 13 Audi V8 PT 3.6 registered in Denmark, so they have absolute no experience.

Well.. let me describe the problem.. The car can be started, and the engine can run at idle speed, but not smoothly. If you touch the speeder to hard, the injectors send a shower of gasoline in, and the engine drowns. To start again you kneed to empty and ventilate the engine for excess gasoline – it is really drowned big time.

And what have I done – well – I have diagnostic equipment (a palm based system, that equals VAG 1551), and it tells me that there is no signal from the HAL sensor G40. (Hal geber). I have tested the hal unit numerous times, exchanged it with a unit from my spare V8 car, and finally exchanged it with a brand new unit.

All wiring has been tested 10 times (The 3 wires going to the ECM (motoronic computer unit) 1 to 12, 2 to 8 end 3 to 19.) The voltages going from ECM to Hal has been tested. 5.2 V between 1 and 3 and 4.9 V between 2 and 3. And the output signal between 1 and 2 was tested with a diode signal tester. Finally the ECM was exchanged with the one from my spare V8.

But still I got the G40 error. Then I tried to “blink” out the errors codes the old fashioned way and got code 2113 witch equals G40. To be absolutely sure I tried a real VAG 1551 and still got G40.

The really strange thing is that the symptom from the engine does not fit to a G40 error. This error should give bad performance, but not at fatal drowning. So I decided that the G40 error must have been a ghost from something else.

The diagnostic system shows NO other errors than G40.

Now I have exchanged EVERYTHING relevant (E.g. relays, fuses, ignition parts, gasoline pressure regulator, new gasoline filter, gasoline pump, air mass meter, idle valve, throttle position senor unit, RPM sensor, crankshaft position sensor, oxygen sensor (lambda) etc. etc) with the corresponding part from my spare V8. (Remark – my spare V8 was driving perfect when I took it home from Germany some months ago.)

The oxygen sensor is almost new - 5000 km and show no errors. Despite that I’m almost 95 % sure that both my air mass meters are OK, I exchanged with a new one – cost a fortune, but the f..!#%"¤%"#¤%"# car can still not drive.

So now I ask thy – without greater hope. Do anybody here ever tried a similar odyssey, and does anybody have a good suggestion? My next step will be to exchange the entire engine wiring assembly.

If this also is without result, I burn the car and buy a French car – they are at least supposed to do this kind of things. To look at a non functioning Audi V8 for 3 months, is like being buried alive.

You are welcome to answer in German. I can read and understand this, but I only speak and write english.

With regards

Lars

Hello Lars,

My guess is the Fuel Pressure Regulator. You said you moved it from your parts car, but perhaps it was bad (or moving the part from V8 #1 to V8 #2 caused it to become bad).

When a FPR fails, it can allow fuel to fill up the cylinders ; if you start the motor with the cylinders full of fuel, it will break several teeth off of the flywheel and you will not be able to drive the V8 over 3000rpm because the timing sensor (OT gaber) will not be able to read the missing teeth correctly.

My friend has created a webpage with instructions here:
http://www.geocities.com/cobramsri/Regulator.html

The only other problem I can think of is one (or more) fuel injectors.

Good luck!

Regards,

- Jeremy

Hello,

My gues is also the fuel pressure regulator, you can get it in aBosch service center, the part number is 0 280 160 298

gruss , jm

Hi Jeremy,

not the Ignition Point Sensor (OT-Geber) needs the teeth of the flywheel but the flywheel sensor does (Drehzahlgeber).

The Ignition Point Sensor needs a small pin mounted on the flywheel passing the sensor at every 360 degree turn of the flywheel. This pin indicates the OT-position of cylinder 1. So the OT-sensor is needed for two things: To indicate when the first ignition has to be done and for a proper indication of the crankshaft position together with the flywheel sensor (in this role the OT-sensor only is a kind of "helping" sensor or error corrector). Without the signal of any of them the engine won't start (or won't run).

So I have another thesis but it has to be noticed that this is quite unlikely: The G40 is, as far as I know, also a kind of error corrector or correction value between the position of the camshafts and the crankshaft position (measured by the flywheel sensor and the ignition point sensor OT). What if the relation between crankshaft and camshaft is incorrect (resulted from a damaged or wrong calibrated toothbelt (sweep)) and as a result the Motronic thinks that G40 is damaged (does it say implausible signal or no signal).

So is Lars sure that there is no mechanical damage at the engine and the camshafts turn as well when trying to start the engine? Perhaps it would be an idea to put the camshaft-coverages away and turn the crankshaft by hand to see if the camshafts are working correctly.

But please notice that this is only speculative.

Hello Bastian

Very good thesis, and also one of the first things I tested, BUT as you indicated - a V8 have an ECM correction test between the OT geber (Crankshaft position sensor) and the HAL geber (The camshaft position sensor). If the 2 set of signal not arrive synchronized, then an error indicating that the toothed belt is out of sync is reported (2114, and my error is 2113). By the way - on a V8 there are 3 different places where it can be out of sync.

This can be controlled visually on a marking on the front poly belt pulley wheel, and on separate markings on the to ignition distributors, that are placed on each of the two inlet camshafts. I of course did this in the very beginning.

But thanks for your suggestion anyway. What I sometimes consider is if the toothed belt tensioners could play me a trick, but then again – the ECM should report another error.

And finally – these possible problems and thesises still not correspond to the fact that the engine drowns when I try to push the speeder, but it can run at idle speed.

Regards

Lars.

Hi,

hmm, maybe two different errors have occured: At first the fuel-injection problem with overfilling your cylinders (not my business, no experiences).

And: Your "Drosselklappenpontiometer" is broken. Why: At my first V8 in 2002 I've cleaned the engine block with high pressure. After that I had strange problems when I raised the throttle. The engine didn't shutdown, but hardly did, and whenever I slowly accelerated everything was fine. When trying to accelerate fast, the engine hardly was able to hold idle speed and it was like pressing the brake instead of getting forward (like a wild horse . Perhaps you check the connector of the "Drosselklappenpotentiometer" beyond the idle speed valve in front of the engine or check the "Drosselklappenpotentiometer" itself (sorry, don't know the English expression). This error wasn't found in my fault-memory at readout!

At all I'd say that not every error is saved in the memory. I had the strange problem that a Hall-sensor was broken but not written to memory - not funny to find that error. Don't only rely on the self-diagnostic-abilities of the Motronic!

Greets

Bastian

Hi Jeanmarie and Jeremy

The Fuel Pressure Regulator IS a good guess, BUT it is not necessary to change this part in case of suspicion - it can be tested using a fuel pressure gauge.

For a couple of weeks the local Audi dealer had the pleasure of looking at my car, but without any result. So now I took it home again and await their test report. One of the things I asked them to test was the fuel pressure.

So far I only know that it - as I expected - was perfectly normal.

And no - I didn’t try to start an engine full of fuel. I can start and it is running at idle speed, but when I touch the speeder it drowns on the spot.

The flywheel teeth and the flywheel OT signal pin are tested. Both the OT sensor and the RPM sensor are also tested.

Thanks for your replies. You can still turn out to be right, if the fuel pressure turns out to be to heigh, but I very much doubt this is the case.

Regards

Lasse

Hi Bastian

You must refer to the Throttle position sensor. This sensor has been moved from one of my cars to another. With no result.

I have also tested the wiring to this sensor. (It is really 3 sensors in one.)

BUT – I’m still not quite sure – you could turn out to be right!!!

Regards

Lars

Hi,

yes, I mean the Throttle position sensor - thanks .

Well, just a guess, but the idle-regulation valve in front of the engine closes when the throttle valve opens (when accelerating) and starts to regulate again when you take back the throttle. So, what if the mechanical connection (isn't it a flexible shaft?) between the throttle sensor in front of the engine and the throttle valve at the back of the engine is well indeed, but the throttle valve itself is broken?

Just imagine: You accelerate, the throttle sensor measures acceleration, the Motronic closes the idle speed valve in front, injects fuel but: no fresh air is taken in cause the throttle valve remains closed due to a mechanical defect! It nevertheless doesn't explain why you have the G40 in your fault memory, but that could be another problem. It's worth a look!

By the way: The G40 and faults in relation to it seem to have very different effects - Thomas Müller here in this forum e.g. drove around without the Hall-Sensor even connected and it worked quite properly. A mate of mine found a defected Hall-Sensor as reason why his V8 even wasn't able to start up any more!

My guess is, relying on the Self-Study-Programs of the Audi V8 which say that the Hall Sensor, Ignition point sensor and flywheel sensor are together part of a redundant self-healing system, that it depends on the condition of the other sensors how a defective Hall sensor results.

Do you have the Self-Study-Programs for the Motronic and so on? If not, send me a private message including your mail address and I'll pass them to you.

Yours

Bastian

Hello again Lars,

I have searched through 16.000 emails about the V8 for code 2113 and found this reply from Kieth T., the most famous V8 mechanic in the US (he has worked on hundreds of Audi V8s):

"In a message dated 4/6/04 8:21:13 PM Eastern Daylight Time, lyddall writes:

> I got a new distributor and installed it last night to replace the
> one with the broken hall sender. ($80 from Force5 and a replacement
> door mirror unit for $25). I still have the same problem of really
> rough idle and hesitation/engine vibration when you push the gas. The
> fault code is
> 2113 (hall sender), but I've tested the sender and it is blinking when
> it should and seems to have the correct voltages as described in the
> shop manual.

This certainly sounds familiar..... Rough idle, hesitation, fully operational hall sensor being coded..... Last time I saw saw those three symptoms together the T/B was off a tooth. The ecu only looks for the hall sensor during a specific period of time, if it doesnt see it during that time it codes the sensor, backs off the timing, and ignores the knock sensors."

I think your timing belt is off by one or more teeth. I also think your have a seperate fuel problem (either FRP or injector). I am sorry to tell you this is not an easy or inexpensive fix.

Good luck Lars.

Regards,

- Jeremy

Hi,

I'd also think about checking that - it should be quite simple by checking the OT-marking-positions on both camshafts and the crankshaft. My other idea is the speed throttle valve.

By the way, Jeremy, off topic but interesting: How many V8 have been sold to the US and how many are still being driven?

Yours

Bastian

Bastian,

Of the 21.565 produced, the US (Canada included?) received 3.868; 0 1989 cars, mostly 1990 cars, and fewer than 550 1992-1994 cars (all of these had the 4,2).

MfG,

- Jeremy

Hi Jeremy,

thanks for the quick reply - so here's my next question: Where did you fetch this data from? Because a few years ago I tried to find out how many V8 have been exported to Australia, Great Britain, Ireland and Japan - but Audi said there's no way to get this information without manually examine the microfilm archives.

Thanks!

Bastian

Hello Gents,

Even if this is also off topic, but I cant help it. I find this oversea assistance just great and I am even more impressed by the fact that in the country where a V8 engine is nothing special really (USA) an Audi V8 finds his friends. Jeremy I just had a good look on your website. Keep it up and whenever you need to know some special prices regarding spare parts besides your special Audi Connection just let me know. I am pleased to help as I am living very close to the main USA transshipment port back here in Germany. Even talking @Lars I hope you can solve your problem quite soon.

Hi Jeremy

As I ealier replyed to Bastian, there are 3 different places where the the toothed belt can have skiped a tooth.

This can be controlled visually on a marking on the front poly belt pulley wheel, and on separate markings on the to ignition distributors, that are placed on each of the two inlet camshafts. I of course did this in the very beginning.

I know your thesis sound very sound, so I better check it again. What I consider is if the toothed belt tensioners could play me a trick, but then again – the ECM should report another error.

And finally – these possible problems and thesises still not correspond to the fact that the engine drowns when I try to push the speeder, but it can run at idle speed.

Regards

Lars.