Paul Bakker

Hi.
Recently I posted a topic about a irregular idle problem on a '90 S4.
This problem solved itself by disconnecting the main ground battery lead and reconnecting it again a couple of seconds later.
The computer reset solved the problem as it seemed.

Now, one week later the problem suddenly came up again so I thought "what's the connection between then and now ?".

Both times the problem came up the car was in EXACTLY the same place.
I now recall I had some problems with other cars recently when trying to wireless close the doors remotely. This place is nearby a WIFI hotspot and/or a public indoor kids playground with heavy machinery.
Coincidence or not but also a fuse blew in this spot this afternoon. So I had a blown fuse AND a stalling engine (twice) at almost the same time. The fuse isn't a fuse of the car itself but from an aftermaket option (lights-on reminder + a Valentine One radar device) Spooky....

So I thought: Is the computer maybe jammed/scrambled by electromagnetic interference on that exact spot ??
Are there any rennlist posters/reader who reconise this problem ?
Can the computer get upset by external signals ????
Any thoughts about the fuse ?


Thanks, Paul

WallyP

The Bosch injection system is a development of the Bendix ElectroJector system, developed in the USA in the mid-fifties. The early test cars has a trunk full of vacuum tube electronics to run the injection, and the engine would quit dead every time that they went under a high-voltage line. Pretty soon, the test engineers knew the location of every high-voltage line in the area...

The first production car with electronic injection was a '57 Rambler Rebel.

John Speake

The fuel and ignition ECUs are well protected against EMC. A WiFi setup wouldn't be powerful enough, and the frequency too high to affect these units.

If you drive up to a FM radio transmittier mast or similar, you might get an effect, but I doubt it. Both units have all their in/out leads fiterered and they are housed in screeened boxes.
On this second accasion of "rough idle" have you had to reset the battery ground again ?

Alan

I think you are jumping to conclusions here... EMI does not blow fuses so rule that out - its a complete red herring...

If you were running with the ECU covers off or had modified the circuits to compromise the shielding or were in an area of extreme EMI - I might consider it possible.. But a WIFI network or normal heavy machinery.. I think very very very unlikely...

You'd need a giant magnetron for that kind of interference - and then your ECU's would not be your primary worry...

I'd consider it much more likely that you have a poor power connection issue... check your power feeds and grounds & clean them all. If the ECU's or dash see a big voltage droop it can screw them up requiring a power off/on reset. Was there a rough road surface at this location or some unique physical condition....

check battery, ground straps, starter, alternator, jump post, CE panel top, CE connectors, ECU connectrors, other grounds esp. at CE panel

Alan

Paul Bakker

Some more specific info about the scene and problem.

A couple of weeks ago the first thing I noticed was a stalling engine.
After restarting the engine it runned perfect so I parked the car.
Next day I noticed a rough idle after about 75 seconds (with engine temp > 50 degrees).
I "cured" the problem by taking of the minus lead of the battery. I then drove 1 week without any problems.

Yesterday I wanted to park the car in the same spot where I had the stalling engine problems. First suddenly the "lights-on" buzzer strated to whisle. I normally drive with lights on during daytime. In Europe our 928 don't have the lights-on relay installed so mine is a simple aftermaked buzzer.
I was dazzled by the noise and while I was thinking why the buzzer buzzed the engine stalled. I restarted and thought "oh no" I slowly drove further on to seek an empty parking spot when the engine again stalled. I parked the car and left.

Several hours later I returned to the car to see if the irregular idle probled also came back again so I took her for a ride. No problems so I didn't unstrapped the minus from the battery.

The buzzer I mentioned was done by a friend of mine so at this time I didn't know it had a seperate fuse so I checked all fuses in the car. Every fuse was OK. I removed every fuse for a check so maybe by removing every fuse I also disconnected the computer again (I don't know).

As said the car only stalled two times but I found it hard to belive there's no connection between then and now.

The surface:
The surface is indeed different from tarmac. It's grit (pebble stones) so yes it's different but I don't see how this can couse the problem. I drive very slow over it....

Hope this info helps a bit. Keep you informed if something happens.

Thanks, Paul

Lizard928

didnt AO have a problem with something due to some radio noise.....

Paul Bakker

Fuse update.
There is NO fuse blown!

I just drove the car and when I started it the Valentine one radardetector did it's power-up sequence (sounds) so it got power out of the blue....
I turned my headlights on and the buzzer buzzed again and the Valentine one powered off...
Put the lights back off and on again and the buzzer kept quit and the Valentine powered on. Drove the car for 10km without any problems.
Since the buzzer and Valentine were installed by the same guy I'll call him today to ask him how things are connected.....

Thanks, Paul

jon928se

I've experienced EMI (From a failing Sodium Street light) preventing me from starting the car. The remote control for the alarm/immobiliser wouldn't unlock the doors and wouldn't un-immobilise the car. Car had to be pushed out of "range" until the remote would work.

However unless you were very unfortunate I can't see that some RF interference would succesfully re-arm the alarm. And the immobiliser systems are generally such that the relays in them to disable ignition and fuel pump are only activated to break those circuits when the system has not been disarmed and when the ignition is on - once the car is running the immobiliser generally can't stop it running.

Paul Bakker

Hi.
I don't have a remote alarm or central locking in my 928. I experienced it with at least one other car on that spot who wouldn't lock/unlock the doors by remote. Therefor I thought about the EMI on that specific spot.

Thanks, Paul

Jascd

I did read a string a while back about a mechanic tearing his hair out to diagnose an intermittant fault and in the end found out it was some sort of rf/microwave interference. You may be able to search for that, it could be the one lizard931 refered to?

John Speake

I know that when Devek were Sharktuning a car using a ribbon cable the car ran fine in the workshop, as soon as they moved the car outside it cut out. That was due to a local tramitter mast, probably for two way VHF radios.

As the ribbon cable was directly connected to the EPROM socket, then in that case the problem could be expected.

Once the LH and EZK ECUs are cased up and screened, then they are unlikely to be a problem, but other devices like alarms/imobilisers may not be so well screened and filtered, especially when they are not original equiment and have not been tested by Porsche in their cars..

Paul Bakker

Guys,
In retrospect to the problems I have had I think this happened:

Two weeks ago I drove to parkingspace X on lot Y.
At parkingspace X the car stalled couple of times.
I drove the car to another parkingspace on lot Y.
It stood there for a couple of days (it's near a campsite where I own a caravan).
It never stood there before (I own the car just a couple of months and never visited the campsite in this period).
A couple of days late when I tried to leave the lot the car had an irregular idle.
Searched almost a week for a solution until somebody here suggested to disconnect the battery for a couple of seconds.
I did and the problem was gone! Problem solved I thought.

Drove the car without problems for a week until;

Yesterday I came again to parkinglot Y and drove my car to place X.
Suddenly the lights-on buzzer buzzed (my lights were on) as if I forgot to put out my driving lights.
just a couple of seconds later the car stalled.
After restart the buzzer kept buzzing and the car stalled again after a couple of seconds.
Parked the car on another parkingspace on lot Y for a couple of hours.
Went home to check driving experience but everything was fine, no irregular idle.
At home I checked EVERY fuse nearby passenger feet cluster, found NO fuse defect.
Drove back to parkinglot Y but parked the 928 on another place away from spot X.
This morning I left and stange enough the Valentine (which is connected to the same power as the buzzer) got alive again....
Put the lights on and buzzer buzzed, removed key and started the car again and both Valentine and buzzer operated as should be. So all problems gone.

My supposition:

Space X is nearby GSM tower and heavy machinery and is a EMI spot.
When stalling problem began this was due to the immobiliser getting a signal to activate. This would explain why the buzzer and Valinetine went dead. No power.
A few seconds after the buzzer went down the engine stalled due to the immobiliser. Strangely enough there were maybe 3-5 seconds between both problems. Can anyone explain ?
The first time I probably didn't have the lights on so I didn't hear the buzzer.
When problems began 2 weeks ago my car was parked for more then 1 day on lot Y so i presume the computer was heavely bombarded by EMI and therefor devellopped the extra idle problems too.

I intent to not go back to this place for couple of months and see if problems stay away. Then next year I'll try it again on spot X to see what happens.

I've spoken to several guys about the immobiliser going weird and they all say it IS possible the immobiliser kicks in due to EMI. I hope my supposition is true.

Thanks, Paul