Porsche 911 1999 3.4 stalling when hot
Discussion
Is it a sudden occurrence or has it been doing it a while? Lost count of the number of issues caused by rodents lately - sudden onset of running issues after previously running fine..... check for evidence of chewing around the engine bay.
With that covered off, the most likely causes of stalling:
Air leak
- Is the oil cap on; is the seal OK?
- Check around the intake manifold; it has 4 rubber sleeves (joining the resonance tube and throttle housing together) spray some WD40 lightly at the sleeves - do the revs rise?
- Check all the green bungs are in the cam covers (6 on pre 2002 3.4 cars)
- Check the fuel cap is on tight (and the seal is good)
- Do an oil separator test - remove the oil cap while engine is running - do the revs flare or change dramatically? If the separator has failed the intake air is taken directly from crankcase (leading to smoke on start, poor idle and sometimes a high pitched whistle - as air is drawn in past the rear main seal!)
- cable throttle engine; check idle stabiliser valve operation - load up the electrics(blower on full, heated rear window, AC on, headlights on main beam, heated seats?), the parasitic load from the alternator will force the idle stabiliser to open to speed up idle (can be removed and cleaned up if necessary)
MAF sensor - less likely for stalling but does the engine stumble higher up the rev range when accelerating? If it does switch the ignition off and unplug the sensor fitted in the airbox. Running without a MAF sensor takes away any adaption influences.
With that covered off, the most likely causes of stalling:
Air leak
- Is the oil cap on; is the seal OK?
- Check around the intake manifold; it has 4 rubber sleeves (joining the resonance tube and throttle housing together) spray some WD40 lightly at the sleeves - do the revs rise?
- Check all the green bungs are in the cam covers (6 on pre 2002 3.4 cars)
- Check the fuel cap is on tight (and the seal is good)
- Do an oil separator test - remove the oil cap while engine is running - do the revs flare or change dramatically? If the separator has failed the intake air is taken directly from crankcase (leading to smoke on start, poor idle and sometimes a high pitched whistle - as air is drawn in past the rear main seal!)
- cable throttle engine; check idle stabiliser valve operation - load up the electrics(blower on full, heated rear window, AC on, headlights on main beam, heated seats?), the parasitic load from the alternator will force the idle stabiliser to open to speed up idle (can be removed and cleaned up if necessary)
MAF sensor - less likely for stalling but does the engine stumble higher up the rev range when accelerating? If it does switch the ignition off and unplug the sensor fitted in the airbox. Running without a MAF sensor takes away any adaption influences.
Porschekiduk said:
Hi i presume its a none Egas car, the idle stabiliser is available as a separate unit.
There could also be some codes or actual values,which can be looked at with diagnostic test kit.
Chris
Hi Chris thanks for the reply There could also be some codes or actual values,which can be looked at with diagnostic test kit.
Chris
I’m guessing it’s a none egas set up
Where is the isle valve located as I did assume this but wasn’t sure if it had one?.
Thank you
Pope said:
Is it a sudden occurrence or has it been doing it a while? Lost count of the number of issues caused by rodents lately - sudden onset of running issues after previously running fine..... check for evidence of chewing around the engine bay.
With that covered off, the most likely causes of stalling:
Air leak
- Is the oil cap on; is the seal OK?
- Check around the intake manifold; it has 4 rubber sleeves (joining the resonance tube and throttle housing together) spray some WD40 lightly at the sleeves - do the revs rise?
- Check all the green bungs are in the cam covers (6 on pre 2002 3.4 cars)
- Check the fuel cap is on tight (and the seal is good)
- Do an oil separator test - remove the oil cap while engine is running - do the revs flare or change dramatically? If the separator has failed the intake air is taken directly from crankcase (leading to smoke on start, poor idle and sometimes a high pitched whistle - as air is drawn in past the rear main seal!)
- cable throttle engine; check idle stabiliser valve operation - load up the electrics(blower on full, heated rear window, AC on, headlights on main beam, heated seats?), the parasitic load from the alternator will force the idle stabiliser to open to speed up idle (can be removed and cleaned up if necessary)
MAF sensor - less likely for stalling but does the engine stumble higher up the rev range when accelerating? If it does switch the ignition off and unplug the sensor fitted in the airbox. Running without a MAF sensor takes away any adaption influences.
Hi, it’s been ongoing for over a year and a half now!. Fuel cap is on but I’ll get him to check the seal. With that covered off, the most likely causes of stalling:
Air leak
- Is the oil cap on; is the seal OK?
- Check around the intake manifold; it has 4 rubber sleeves (joining the resonance tube and throttle housing together) spray some WD40 lightly at the sleeves - do the revs rise?
- Check all the green bungs are in the cam covers (6 on pre 2002 3.4 cars)
- Check the fuel cap is on tight (and the seal is good)
- Do an oil separator test - remove the oil cap while engine is running - do the revs flare or change dramatically? If the separator has failed the intake air is taken directly from crankcase (leading to smoke on start, poor idle and sometimes a high pitched whistle - as air is drawn in past the rear main seal!)
- cable throttle engine; check idle stabiliser valve operation - load up the electrics(blower on full, heated rear window, AC on, headlights on main beam, heated seats?), the parasitic load from the alternator will force the idle stabiliser to open to speed up idle (can be removed and cleaned up if necessary)
MAF sensor - less likely for stalling but does the engine stumble higher up the rev range when accelerating? If it does switch the ignition off and unplug the sensor fitted in the airbox. Running without a MAF sensor takes away any adaption influences.
Revs drop when this happens!.
Struggles to start and go, 15 minutes and it’s running normal again although I’ve smelt unburnt or a rich mixture like my old gtturbo does.
I’ll get him to check the oil cap removal as idle should change when caps off.
No air whistling leaks from what I can self hear.
Car runs fine on higher revs and runs fine otherwise.
It’s been to design 911 and he said less likely the maf sensor.
I’ve tried the air mass off but no change.
Cheers
captainblakk said:
Could be a Variocam adjusting solenoid, they don’t always store a fault when they fail,
it’s cam cover off to replace them though, and then you may need to battle with badly corroded exhaust nuts and bolts
To add to Captainblakk's suggestion the chain guides on the variocam adjuster itself can break up - with the solenoid and tensioner still working - a quick check is to drain the oil into a clean pan and check for debris; then drop the sump pan and look in the oil pick up or pan itself for little bits of brown plastic - if you find any you'll know without taking the cam covers off they'll need attention.it’s cam cover off to replace them though, and then you may need to battle with badly corroded exhaust nuts and bolts
For reference:
http://986forum.com/forums/boxster-general-discuss...
Had a few like that; injectors leaking when hot /under pressure - floods the engine after switch-off and unless left til cold again subsequent restart after a delay results in extended cranking, fluffing and throttle input to catch and clear it.
Easiest check is to put a fuel pressure gauge on the end of the rail (there's a schrader valve on the end for measurement) or lift the injectors out and check the ends for signs of leaking - would explain the smell of fuel too.
I have had them go full open too - masses of dense white smoke!
Easiest check is to put a fuel pressure gauge on the end of the rail (there's a schrader valve on the end for measurement) or lift the injectors out and check the ends for signs of leaking - would explain the smell of fuel too.
I have had them go full open too - masses of dense white smoke!
Pope said:
Had a few like that; injectors leaking when hot /under pressure - floods the engine after switch-off and unless left til cold again subsequent restart after a delay results in extended cranking, fluffing and throttle input to catch and clear it.
Easiest check is to put a fuel pressure gauge on the end of the rail (there's a schrader valve on the end for measurement) or lift the injectors out and check the ends for signs of leaking - would explain the smell of fuel too.
I have had them go full open too - masses of dense white smoke!
Thank you for the info Pope, I’ve messaged my brother and let’s see how he deals with it in Cyprus as I’ve told him what’s been said and waiting in his response or maybe he should take it to one of the local garages and see what they come up with Easiest check is to put a fuel pressure gauge on the end of the rail (there's a schrader valve on the end for measurement) or lift the injectors out and check the ends for signs of leaking - would explain the smell of fuel too.
I have had them go full open too - masses of dense white smoke!
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