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Gorthaur

986 S problem at idle, engine won't rev and shakes, battery discon

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Hi guys,

I’m writing from Italy, owner of a 2000 986 S, 84.000 km on the clock.

First of all, I have to apologize for my poor English.

Recently I had my cluster bulbs replaced thanks to the good DIY guides found over here, so, thank you so much for helping us all with your knowledge and patience.

In order to do the job, since my car features the optional alarm, I previously disconnected the negative cable of the battery while leaving the ignition key on position 2 as read on the board in order to avoid the siren to scream (is this correct, BTW?).

With the cluster back in place, without touching the key nor the gas pedal, I connected the negative cable and found everything was fine, then I waited for a few minutes with the key still in position 2 thus letting the e-pedal to reset itself, and eventually removed the key and left the place.

Two days later I picked the car up but the engine was really strange at idle. No fault lights on the cluster but no power at all, it hardly reached 1600 – 1900 RPM with the aircon switched off even if I floored the pedal.

The whole car shaked violently but the engine didn’t stall. If I pushed on the gas pedal, it revved a little making a smoother noise and behaving normal, but just up to 1600 – 1900 RPM. It seemed there was something at work avoiding the engine to rev.

Tried several times to do the 1-minute procedure, tried to fire it up and swich it off a million times, then called the local PD but received nothing but a “shame on you for having disconnected the battery”.

Called an indi whose suggestion was to blindly replace the MAF (...even though the problem was showing itself at idling and not over 4000 RPM).

Eventually phoned another indi; this nice chap came, attached a small diagnostic device to my car and told me there were no error codes displayed. After half an hour the engine got warm and everything was perfectly normal, so he invited me to drive the car for some thirty minutes and so I did.

Problem is, though, yesterday the issue came back again and didn’t go away even after a million 1-minute procedures, dozens of key-on-0-to-key-on-2.

I haven’t got access to a Durametric.

When I set the key on position 2 I hear a very low “buzz” which goes on forever, until I fire the engine.

I’ve got a GPS from my Insurance Company on the positive pole which I cannot remove.

What do you suggest? I’m really struggling… Shall I disconnect the negative cable and leave it aside for a few days, as read over here? What must I do when disconnecting the battery in order to avoid the alarm to wake everybody up?

Thank you in advance for your help, I really need it!

Cheers,

G.

P.S. If you reckon it would help, I can record the engine noise and attach a file...

Edited by Gorthaur

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Sounds like you need to adapt the throttle as follows-

With the battery connected, and without touching your throttle,. switch the key on for about 1 minute or more, the switch the key off for at least 10 seconds, again dont touch the throttle during this process. then start it let it idle for a couple of minutes then try your throttle again and let us know with the results

Edited by harryrcb

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Sounds like you need to adapt the throttle as follows-

With the battery connected, and without touching your throttle,. switch the key on for about 1 minute or more, the switch the key off for at least 10 seconds, again dont touch the throttle during this process. then start it let it idle for a couple of minutes then try your throttle again and let us know with the results

Thanks Harry. Unfortunately I've done that procedure a million times without any improvement... :(

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Sorry did not realize that, Has the car been sitting for some time? You can get corrosion build up on your contacts. Its worth a try take you DME plug off and on several times to try to clean the contacts also the alarm under your seat.

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Hi guys, unfortunately I've goy no access to any Durametric or diagnostic tools. :(

Till the day before the cluster job it was running perfectly and so it did when the mechanic managed to let it idle normally. I drove the car for 30 minutes and everything was fine. It seems like the guy thanks to his device managed to clear a fault which woke up again on the very next ignition.

Edited by Gorthaur

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Sorry - but you are just throwing rocks in the dark hoping to hit something. Pure guessing...

You need to see what is going on with a diagnostic tool.

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Hi guys.

yesterday I went to pick the car up in order to put some juice in the tank.

I started it and the problem was still there. I managed to drive it to the petrol station but on my way I decided to go through some gears and found that in first gear I could do 20 kph, 30 in second, 40 in third and so on. So I decided to upshift and downshift a few times and something better seemed to happen but then... I reached the station.

I put 20 liters in the tank, then did the 1-minute procedure with the key, started the car and...

...BANG! White smoke and oil all over the place!!!

Just kidding!!! I started it and she was perfectly fine! I drove it for half an hour, then came back home. Turned it off, waited for a few minutes and then started it again. Everything ok.

Tomorrow I'm going to check her again but for the moment I'm very, very pleased!

What do you reckon? Fuel level too low? Bad fuel? Who knows... But, as far as the problem doesn't appear again... who cares!!!

I'll keep you updated, thanks again for your help!

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Sorry for raising an old topic, but I have exactly the same issue now. The problem occurred after running out of fuel.

Did adding fuel really solve your original issue permanently? 

Started a new thread on this here:

 

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I'd check the fuel pressure.  Running the car out of gas can suck tank bottom debris in the filter, clogging it.  It can also burn up the fuel pump.

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