986 S 2000 will not rev and idles rough, after run out of fuel

[oojanen]

Hi,

 

Car is Boxster S 2000 Tiptronic.

Last evening I drove the car for 10min and probably ran out gas, car stuttered and engine stalled (due to faulty fuel tank reader, runs out when shows 150km left or 1/4 tank. It showed 180km when I departed, so I thought I would have enough to the gas station). I put in 4 liters or so of probably 2-yr old fuel from a canister I keep in the car. It has run out of gas 1-2 times before, but no problem. Car started up again, but with complete loss of power and very rough idle. I drove to gas station 2km away and filled up. But the problem persists. I could drive roughly 10kph with gear 1, 20kph with 2, etc. and it will not rev at idle more than 1900-2000rpm, today went up to 2500rpm at idle when warm. It has almost no power at all, and accelerates very slowly. Idle remains pretty rough when cold, but stabilizes when warm but still clearly not healthy, makes a hollow low frequency idle with the car shaking. The symptoms seem as if it would not fire on all cylinder and/or run on a very lean mixture, even now when the tank is full. ? It feels as if the car was in some kind of a limp/safe drive mode. I don't have access to fault code reader immediately. Any ideas what this could be?

I guess it can't be the fuel pump or filter since the engine still runs? Running out of fuel cannot cause MAF or ignition coil issues? The 4 liters of somewhat old fuel is not a likely problem either I guess, and it is not mixed with new one anyway. It really feels like an electrical motor control or fuel mixture problem.

Is there a way to make a complete reset of ECU, MAF, e-gas and what not - I've already disconnected negative battery terminal for 12hrs and that did not help.

 

The problem is exactly the same as this one (solved by simply filling up the car, did not solve it for me...)

 

 

I've tried the 1-min procedure with ignition on for 1min. then off for 10sec. but it does not help. I have also already disconnected battery.

What can break when car runs out of fuel? Or could it be that something else broke first, and I just think it ran out of fuel (but then again engine stopped, and restarted when I added fuel so probabilities are it was a fuel issue in the first place)

 

I am really out of ideas, will try to disconnect the MAF and start engine without to see if that has any effect, but I don't think so...

 

 

http://986forum.com/forums/general-discussions/38024-986-s-problem-idle-engine-wont-rev-shakes-battery-disconnected.html

 

[wizard]

In the absence of a code reader, cleaning the MAF would be my first course of action. Not too difficult a task, but care in handling and the appropriate cleaner needed.

 

 

[JFP in PA]

4 hours ago, oojanen said:

Hi,

 

Car is Boxster S 2000 Tiptronic.

Last evening I drove the car for 10min and probably ran out gas, car stuttered and engine stalled (due to faulty fuel tank reader, runs out when shows 150km left or 1/4 tank. It showed 180km when I departed, so I thought I would have enough to the gas station). I put in 4 liters or so of probably 2-yr old fuel from a canister I keep in the car. It has run out of gas 1-2 times before, but no problem. Car started up again, but with complete loss of power and very rough idle. I drove to gas station 2km away and filled up. But the problem persists. I could drive roughly 10kph with gear 1, 20kph with 2, etc. and it will not rev at idle more than 1900-2000rpm, today went up to 2500rpm at idle when warm. It has almost no power at all, and accelerates very slowly. Idle remains pretty rough when cold, but stabilizes when warm but still clearly not healthy, makes a hollow low frequency idle with the car shaking. The symptoms seem as if it would not fire on all cylinder and/or run on a very lean mixture, even now when the tank is full. ? It feels as if the car was in some kind of a limp/safe drive mode. I don't have access to fault code reader immediately. Any ideas what this could be?

I guess it can't be the fuel pump or filter since the engine still runs? Running out of fuel cannot cause MAF or ignition coil issues? The 4 liters of somewhat old fuel is not a likely problem either I guess, and it is not mixed with new one anyway. It really feels like an electrical motor control or fuel mixture problem.

Is there a way to make a complete reset of ECU, MAF, e-gas and what not - I've already disconnected negative battery terminal for 12hrs and that did not help.

 

The problem is exactly the same as this one (solved by simply filling up the car, did not solve it for me...)

 

 

I've tried the 1-min procedure with ignition on for 1min. then off for 10sec. but it does not help. I have also already disconnected battery.

What can break when car runs out of fuel? Or could it be that something else broke first, and I just think it ran out of fuel (but then again engine stopped, and restarted when I added fuel so probabilities are it was a fuel issue in the first place)

 

I am really out of ideas, will try to disconnect the MAF and start engine without to see if that has any effect, but I don't think so...

 

 

http://986forum.com/forums/general-discussions/38024-986-s-problem-idle-engine-wont-rev-shakes-battery-disconnected.html

 

I would take a look at your fuel filter; running the car out of gas can suck all the bottom debris from the tank into the filter.  Running it out of gas can also burn up the fuel pump as well.

[oojanen]

Fixed it! 

Spent 5 hours googling this today, but found the solution!

There are numerous threads on this (or related) issue which seems to culminate to the error code P1502 (P1502 Throttle Jacking Unit, Spring Test – Above Limit). I did not check if I had that, but am pretty sure based on all the symptoms.

Most people get these after disconnecting the batter for a more or less extended period of time. Myself and at least one other author got it from running out of fuel.

Also, seems to particularly plague the model year 2000 S. 

An then the solution, which was found on this thread (only): 

Solution: Turn the ignition on and off pretty fast for about 20 times, without starting the car. Then just go and start the engine, and Voila - it runs perfectly!

Yes, you read right. I couldn't believe it myself. Most people seem to have by the time they found this solution exchanged throttle body, fuel pump, even DME...

The thing seems to relate to a bad software on the "throttle jacking unit", which after failing for one reason or the other, does not really recover easily. No idea how and why the ignition on-off-routine helps the recovery procedure, though...

I am really relieved and huge thanks to Nick2508 for originally solving this!