I started my GTS and let it idle in the garage as it came up to temp. After a couple of min it began running rough and died. The low oil warning was illuminated after the car died. I checked the oil level and it was below the low notch on the dipstick. I checked for leaks, none were found. I thought the low oil was strange because I keep the car topped up regularly.

since there were no leaks found, I decided to wait to see if the oil was all up in motor and heads. Sure enough after waiting for an hour the level on the dipstick was at the top notch.

im curious what the hell is going on, I’ve never seen this behavior before. I figure it has something to do with it being cold, temps in the thirty’s and the oil being thick - 20w50 synthetic. Or maybe because I didn’t rev the motor as if I was driving it?

or is there something else going on? I drove the car last week and it as just fine.

 

NOTE dont run the engine to warm up the car. A rough running event could smoke the cats and cause a fire
Instead , Start the engine and after 30 seconds drive off at a reduced rate till the engine reaches running temperature.

NOTE with cold temps a considerable amount of water can be produced inside the crankcase,
and if the engine doesnt reach operating temperature and then maintain it for 20 mins or more,
then the water will stay in the oil.
With a stored car its better to leave it alone till you can properly drive it for 30 mins.
NOTE charge the battery every so often so its ready to go
NOTE on an S4 and later disconnecting the battery then connecting it will reset the computer/ MAF/ O2 parameters.
so it will have to relearn those .
Making a few full throttle on the pedal runs will reset these parameters
NOTE you dont have to go to hi RPM but rather full pedal travel and reach about 4500 RPM, do this in lower gears so you dont speed./

 

Or just leave it on a Battery Tender that monitors the state of charge and stops charging when full then charges at low amperage again when it needs it. I leave all my Porsches on Battery Tenders all the time. Got 12 years out of my last AGM battery in my 914 and 8 years out of two AGMs in my 997. The one I put into my 928 in 928 in 2015 is still in it, so 8 years.

 

My Bet: The IMS relay kicked-in and shut off fuel to four of the injectors. Search on “IMS” for details.

The low oil level warning often triggers when the engine dies (or is started on an incline.)

 

I agree with your diagnosis, it was running rough as though the IMS kicked in. However, this car is not running cats, and has the IMS bypassed using the IMS bypass relay bridge. So I am pretty sure it was not the IMS system engaged. Also, the low oil warning light was verified with actual low oil marking on the dipstick. The oil level in the pan was very low. I am thinking all the oil was up in the motor someplace and not returning to the pan fast enough. Maybe there was too much oil pressure and the heads filled? Can that even happen at idle?

 

Bonjour,
On mine, sometimes, some failure light stay on after starting. I stop the engine and start again and usually it is good after that.
I suppose it happens when the battery is low.
did your car die every time as you describe?
Raphael

 

Well, in that case it's something else causing the rough running as the cold-start enrichment goes away and the o2 sensor control loop kicks in. Those are the clues. TEMP-II sensor, o2 sensor, mass-air sensor are the usual suspects. If you have history for these parts and they are new-ish then less-common issues need to be investigated.

You have three things to investigate:

- why was the IMS system bypassed?
- why is the 928 running rough after cold-start (probably related to the above.)
- oil level mystery

I've never looked into how much oil is sucked out of the sump when the engine is running. Of the top of my head I can't think of a failure mode that would cause what you observe.

Do you have a pan spacer? What form of oil pan gasket do you have? Have you ever replaced the oil cooler hoses or the pressure relief spring for the oil pump?

 

NOTE the oil is not gonna pack the heads at idle maybe at 6 K RPM.
Was the car on a level surface or on a hill for this event?
is this engine stock?
Did you just prior to starting the engine disconnect the battery then reconnect it?
have the head gaskets been replaced?
How cold was the car when you started it?
Do you have a factory O2 sensor installed or a universal?
When was the MAF rebuilt?
When was the LH rebuilt?
Do you have a new CPS made by Bosch?
How old are the ignition wires?
How old are the caps and Rotors are they Bosch?
Was an Intake refresh done to include new knock sensors?
Are they Bosch?
Did you replace the Hall sensor for the cam is it Bosch?
Did you replace the 2 plastic junctions at the MAF boot?
Is the brake booster working correctly?

 

See the colored answers below

The car has been running and driving perfectly over the fall and into winter. I suspect this one-time poor running condition was the lack of adaptation and cold conditions. I have not restarted yet. However, as I was typing my responses above, I guess I could have some rodents that have gotten in and chewed some wires. I'll make a deeper inspection and give the car a restart and drive around for a while.

What gives me more concern is the low oil situation and where it all was and why it wasn't draining back to the pan fast enough. I could hear tapping in the bottom end, like lifter noise but down by the flywheel. Not sure what to make of that. My plan is to take it out for a test drive in the next few days. We are having a bit of bad weather hear between atmospheric rivers and freezing rain.

Thanks all for your suggestions and guidance as always.

 

well the computer disconnect was the equivalent of battery disconnect so starting it and letting it idle without driving off could have caused strange anomalies,
I would disconnect the battery for a min the reconnect it then start the car let it run for about 30 seconds then go drive it easily till it comes up to temp,
then do a few foot to the floor runs
NOTE dont go over 4500 RPM as you will be speeding,
its the foot to the floor to assist with adaptation that you want to get programmed.
You might want to get stock chips when you get the LH rebuilt,
also disconnecting the computers could cause a problem,
add D100 to the connector pins

 

Foot to the floor may clear out the cylinders and warm up the exhaust but the LH and narrow band 02 sensor can only adapt at idle and part throttle at low to medium load.

 

Yes thats why I suggest to drive off easily till up to temp , 8 miles or so
then do a few of the foot to the floor for adaptation.

FWIW I have found 2 LH cars 87 onwards.with funky connections at the computers,
and moving the harness around near the connectors would kill the engine while it was idling.
you might want to try this test as well

 

maybe i missed something, it seems to me that the oil level issue would be from the wrong oil for the weather....too thick, and not draining back to the pan. is the oil color/clarity good (no brown goo)? is the temp well below freezing? 20w-50 doesn't play well with cold temps.

 

Guessing that the oil level warning came on right after the car stalled and it was low. You checked after an hour and level was good. Doesn't necessarily mean the oil didn't get to the pan quicker than that hour. Could have been 10 minutes. Most cars with cold oil will take a bit longer to drain back and with our 8 plus quarts, the oil takes a long time to warm up. Betting your oil issue is not a big deal.
On the stalling, perhaps idle stabilizer being cranky in the cold weather?

 

[QUOTE=
NOTE on an S4 and later disconnecting the battery then connecting it will reset the computer/ MAF/ O2 parameters.
so it will have to relearn those . ./[/QUOTE]

I was not aware that was an issue.
As our car (1987 S4) normally sits for 3-4 days at a time, I normally disconnect the battery.
Is that a problem for the ECUs ??

I have gotten several comments - from "nothing will happen", to "it spikes the voltage to the ECUs"

It would be nice to know what is correct.