Stuttering, lurching, dying 944 S2 engine
Discussion
My recently purchased 944 S2 (see http://www.pistonheads.com/gassing/topic.asp?h=0&a... has been getting me to work and back just fine, but today I suffered the ignominy of an AA callout. I got home, but it's got a major problem and I'm hoping the wisdom of the forum members may help me figure out what it's likely to be.
I was sat at traffic lights for *ages* and noticed water temp was rising a bit (which it has literally never done before - gauge always stays near the bottom) but far from critical. Then just as the lights went green, engine idle speed dropped swiftly to nothing and the engine died. It took a few attempts to get it started again without dying immediately, whereupon I limped to a very close by B&Q car park.
At idle it was oscillating by itself between 900 RPM and almost zero. Sometimes it would pick up again from zero, sometimes it would just die. It was basically undriveable and I had to call the AA man. To his credit, he was great.
We suspected the idle control but disconnected the lead to that and it was still misbehaving in odd ways. Plugged that back in and adjusted the throttle cable to ensure at least a certain minimum RPM. That allowed it to start and not die. But in driving it would frequently stutter and lurch quite violently at speed, and pressing the throttle anything more than very gently caused the car to slow down rather than speed up.
When opening the throttle manually under the bonnet it does rev but you can hear it’s running really rough, and it bogs down first.
Potential culprits:
- That idle control valve - but that wouldn’t explain the non-idle behaviour - especially the stuttering, would it?
- AA man suspects mass airflow meter.
- Fuel filter? But that probably wouldn’t fit with the rhythmic oscillation between high and low RPMs. If fuel was being starved I’d expect very different characteristics.
- Something else?
What do you think?
I was sat at traffic lights for *ages* and noticed water temp was rising a bit (which it has literally never done before - gauge always stays near the bottom) but far from critical. Then just as the lights went green, engine idle speed dropped swiftly to nothing and the engine died. It took a few attempts to get it started again without dying immediately, whereupon I limped to a very close by B&Q car park.
At idle it was oscillating by itself between 900 RPM and almost zero. Sometimes it would pick up again from zero, sometimes it would just die. It was basically undriveable and I had to call the AA man. To his credit, he was great.
We suspected the idle control but disconnected the lead to that and it was still misbehaving in odd ways. Plugged that back in and adjusted the throttle cable to ensure at least a certain minimum RPM. That allowed it to start and not die. But in driving it would frequently stutter and lurch quite violently at speed, and pressing the throttle anything more than very gently caused the car to slow down rather than speed up.
When opening the throttle manually under the bonnet it does rev but you can hear it’s running really rough, and it bogs down first.
Potential culprits:
- That idle control valve - but that wouldn’t explain the non-idle behaviour - especially the stuttering, would it?
- AA man suspects mass airflow meter.
- Fuel filter? But that probably wouldn’t fit with the rhythmic oscillation between high and low RPMs. If fuel was being starved I’d expect very different characteristics.
- Something else?
What do you think?
It gets worse. I've not tried to start it since then, but it's booked into the garage for Wednesday.
However the cobra alarm started beeping continuously (beep, beep beep) this morning as it was sat on the drive. Nobody was near the car. It’s not a loud siren beep, but loud enough to be annoying for us and our neighbours and to stop people walking by.
If I open any door, the beeping stops. But it starts again as soon as the door is closed. The button on the fob doesn’t do anything, and the ignition is dead. The red alarm LED is lit constantly.
Does this indicate a problem with the car battery? It's not had any battery problems before, but maybe whatever calamity caused the breakdown is now draining the battery?
Are there any ways to work around the alarm problem that don't require leaving the car door open - that being the only way to silence it right now?
However the cobra alarm started beeping continuously (beep, beep beep) this morning as it was sat on the drive. Nobody was near the car. It’s not a loud siren beep, but loud enough to be annoying for us and our neighbours and to stop people walking by.
If I open any door, the beeping stops. But it starts again as soon as the door is closed. The button on the fob doesn’t do anything, and the ignition is dead. The red alarm LED is lit constantly.
Does this indicate a problem with the car battery? It's not had any battery problems before, but maybe whatever calamity caused the breakdown is now draining the battery?
Are there any ways to work around the alarm problem that don't require leaving the car door open - that being the only way to silence it right now?
It seems that the alarm issue was caused by flat battery: 4.5V registered on the multimeter, which is past redemption according to some sources and time to buy a new battery. However I jump started it successfully from the Skoda and it charged back up to 12+ volts after idling fast for 15 minutes. Phew.
However I noticed that the radiator fans came on as soon as I hooked up the Skoda battery to jump start. That’s with ignition off and engine stone cold on the 944. This suggests either the fan relay or the temperature switch have an issue. I guess it was the fans running that caused the battery to run flat in the first place. But how could that possibly be related to the engine issues I described in my original post above? That switch/relay are surely only involved in fan operation. Could it be a symptom of some wider issue? I can’t imagine what. Maybe it was pure coincidence and I really do have several independent things failing all at once all of a sudden, however unlikely that may be.
I do note that immediately preceding the original engine problem in my top post, I had noticed the coolant temperature creeping up as a I sat at the lights. I have no idea if the fan had kicked in or not, but one would only expect the temperature to have been climbing if it had *not* been running. But maybe it just hadn't kicked in *yet* at that point.
For now I have physically removed the fan relay (big silver thing at the back of the fuse box) to prevent the fans from running and killing the battery as it sits in my drive. Obviously this is only a temporary solution. The tests to figure out what is broken on Clarks Garage are not easy for me to conduct since I can't really get at the switch.
However I noticed that the radiator fans came on as soon as I hooked up the Skoda battery to jump start. That’s with ignition off and engine stone cold on the 944. This suggests either the fan relay or the temperature switch have an issue. I guess it was the fans running that caused the battery to run flat in the first place. But how could that possibly be related to the engine issues I described in my original post above? That switch/relay are surely only involved in fan operation. Could it be a symptom of some wider issue? I can’t imagine what. Maybe it was pure coincidence and I really do have several independent things failing all at once all of a sudden, however unlikely that may be.
I do note that immediately preceding the original engine problem in my top post, I had noticed the coolant temperature creeping up as a I sat at the lights. I have no idea if the fan had kicked in or not, but one would only expect the temperature to have been climbing if it had *not* been running. But maybe it just hadn't kicked in *yet* at that point.
For now I have physically removed the fan relay (big silver thing at the back of the fuse box) to prevent the fans from running and killing the battery as it sits in my drive. Obviously this is only a temporary solution. The tests to figure out what is broken on Clarks Garage are not easy for me to conduct since I can't really get at the switch.
Edited by hartlandcarr on Monday 23 May 16:20
Gassing Station | Front Engined Porsches | Top of Page | What's New | My Stuff