Lago Blue

Hi Avi,

a.) It may be helpful to attempt to pull , note and clear any codes. now held in memory. This also ensures any codes thereafter are recent. Do you have a serviceable Check Engine Light (CEL) and the Audi terminal bridging cable to aid you?

b.) Switches, to review:
- Previously, on separate occasions, a mechanic replaced:
i . "Switching device ...front left side to the level of the floor" possibly a relay from the panel forward of driver's outboard knee, correct?; and
ii. Ignition switch, both mechanical and electrical portions, but has been electrically intermittent since replacement, requiring extra key turning and selecting to function, correct? This switch behaviour has now changed to either include or has been replaced by the subject engine failures, which?

c.) Tach behaviour review: I am still not clear whether the indication of engine rpm always/sometimes/never falls to zero at problem onset, while in gear, clutch pedal out and the wheels are still driving the engine, or perhaps does the rpm indication first fall to zero and then perhaps begin to indicate again before the car has stopped?

If you drive with a spare spark-plug , you may perhaps more easily check for spark at the road-side.

aviatore

Hi Lago Blue,
I am sorry that my bad English does not make you understand what I write.

a.) Yesterday I left for work and I will stay away from home for three weeks.
When I return home I will try to pull the codes, hoping that my Audi 80 has the CEL.

b.) i. No. The "Switching Device" is not located in the fuse panel or auxiliary panel, but is located in the passenger compartment, driver's side at the bottom left under the carpet, under the lever that opens the engine compartment. I have a link and a photo of switching, but do not know how to send it.
ii. Yes. The ignition switch again after a few weeks he began to present problems. With the new switch also I changed the key. The question on "...This switch behaviour has now changed to either include or has been replaced by the subject engine failures, which?" I did not understand. You could write it in a different way?

c.) When the failure occurs, the tachometer (rpm gauge) immediately indicates zero value even if the car is still running with the drive shaft connected to the transmission.

The spark-plug have been replaced and are new components.

Thanks for your patience.

Lago Blue

Hi Avi,

Not at all sir, your writing displays the care and focus of an attentive mind with whom I'm happy to communicate! A pleasant change from one who although born and bathed in English, refuses to drink it in or who cannot imagine why they might ever have need of a thought requiring more than 140 characters, to express.

1.) Functional CEL: If your car doesn't have a working CEL, if present, the bulb can be replaced, if not present from the factory, it can be added in or temporarily attached.

2.) Symptom(s) possibly linked to ignition system: Questions and review:

(Ignoring for the moment any issues with the key, lock cylinder and assembly that the ignition switch attaches to.)

a.) - Why was the electrical portion of the ignition switch also replaced?

b.) - Did the replacement electrical switch initially perform differently than previously?

c.) - The replacement switch, although initially working correctly, soon developed an intermittent fault that could be overcome by re-selecting with the key, correct? This behaviour continues, correct or no?

d.) - Is the problem which "now presents itself in a different way", the engine shut-down issue?

e.) - When did the engine quits issue first appear?

Analysis so far:

What I think we have established is that when the engine shutdown issue occurs, the function of the ignition system has been interrupted. Reasons:

- That the tachometer falls to zero immediately when engine quits despite that the still turning wheels are driving the engine to continue turning at this point (car is in gear and clutch engaged) and in an electrically serviceable car, the tach would otherwise continue to be driven;

- That the engine quits suddenly (like the key has been turned off as opposed to running out of gas);

-That the fuel pump is not powered during the quit condition may be a symptom, rather than a cause is as follows:
i.) That the root cause of the engine quitting has stopped the consumption of fuel , the fuel system only knows that it does not need to run the pump, however
ii.) That the pump will not prime (key in first position) during the quit condition; and
iii.) That the fuel pump's momentary operation with the key turned to the first position is restored coincident with engine starting capability with the key in the second position and some period of normal operation tells me that:

The fuel system is performing entirely normally; and
The root cause has control over both fuel pump power supply and the ignition system.

This points to something like the ignition switch, or that particular circuit.

Next steps (for the next road-side engine has quit occasion):

What I had in mind by suggesting you travel with a spare spark-plug was that with it, road-side with the issue, you could pull off a high-tension plug wire at one of the installed plugs, install the spare and lay the wire such that the plug is grounded on top of the engine, and in view when you are inside, partially close the hood to shield the plug from daylight, then...

Check for spark (by cranking the engine).

What you may find is that as long as the problem is occurring, you have no spark. As previously I expect that when the problem vanishes, spark, pump priming and engine starting are all restored together, until next time. If that is the case, it may be that the root cause is something critical to both ignition and pump function which could be several things, but if your ignition switch is already malfunctioning, it may be where to start.

Have a good trip, sometimes a break from an issue offers some insight towards the solution. I hope your battery doesn't go flat while you are away.

To be continued...

aviatore

Hi Lago Blue,
I'm sorry for the delay with which I answer you, but during these weeks using the PC only to see my email.
I thank you for the kind words and for the commitment that you're devoting to solve my problem.
For this reason you have my esteem and my appreciation.

1.) Functional CEL: we will resume this subject when I return home. I am very curious about this argument and would like to learn more.

2.) a.) the Audi service had in stock only the entire ignition switch and whereas the original switch had done his job for more than 23 years, they decided to change it.

2.) b.) Yes.

2.) c.) Initially when the problem occurred, was simply place the ignition switch to "OFF", then reposition it to "ON" and the problem disappeared. The problem happens when I travel on the highway, at high speeds (greater than 80 km/h). Rarely happens the problem when using the car in the city.
Now, is not enough to place the ignition switch to "OFF".

2.) d.)NO. The problem presents itself in the same way. The difference is in the solution of the problem.
At first time was simply place the ignition switch to "OFF", then reposition it to "ON", now I just have to wait (there's nothing I can do).

2.) e.) After few weeks by the replacement of the ignition switch. The Audi service said that the cause of the problem was not the ignition switch but the "Switching Device".

I share your analysis when you say that the cause of the problem is to be found in the electrical system, but I do not think that the cause is the ignition switch. Analyzing the wiring diagram that I found on the internet, into the ignition switch, there are two of the five sections that connect the battery voltage (line L30) to electric utilities car, a section is dedicated to the circuit of the "STARTER", a section is dedicated to power the "SEAT BELT WARNING RELAY" and a last section is not used (not connected).
When the problem occurs, all the equipment is supplied and efficient (blower motor, lights, horn, fuel pump relay, stop lights, power windows, power mirrors, wipers, instrument cluster, etc ...). While, if one of the two sections is not working properly, some users should not work; instead they work their all, including the tachometer result powered, but that probably go to zero because the signal comes from the Motronic Control Unit is absent.

Your suggestion of check for spark (by cranking the engine) is great. The next time will present the problem, will be the first thing I'll do.

Mmmmmmm...... I think that when I get home I'll have to recharge the battery.

Hi, my friend.