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4 problems in 10 minutes...

N

nfearn

Member
It's not my day today, at least as far as the 993 goes.

i) Decided to take it out for a quick run. Felt the cabin needed to be a bit warmer, so turned the heater thermostat up, resulting in the windscreen misting up completely within 30 seconds. Had to pull over to the side of the road to let the mist clear as the screen demist did its thing.

I've noticed this before - if the temperature's turned up I get screen misting for a while. Thoughts welcome.

ii) Engine oil temperature gauge has suddenly stopped registering anything. It has flickered momentarily off the "powered off" position, but then dies almost instantaneously. Does anyone know if there are any weak spots in this circuit (i.e. sender, wiring, 12V supply, instrument itself?).

iii) Most alarming - the car's developed a misfire and loss of power. It was serviced only a few hundred miles ago and seemed fine since. It seems to me that it's possibly running on one distributor - any quick tests for this? (eg relative position of rotor arms?). Otherwise it's probably a three week wait for local indie to fit me in. (Essex)

iv) Cussed rear wiper arm has snapped clean off at the point where the upper (on top) arm joins the part where the wiper blade fits into.

The 944, meanwhile, continues to run without incident....

Nick
 
Yeah, well. I thought I could handle it - I'd dabbled with 944s for years. But pretty soon I needed something stronger. I just wasn't getting the same buzz any more. That's when I thought I'd' "do" a 911....
 
Most indies i ve used wud pop u in for 10 mins and diagnose all those things until they cud do it permanently .......................

For demisting technique .............presumimg air coming out of vents to screen ?
Patience is all , make sure air is also hot, keep going full blast and IT WILL CLEAR .............................if cars been out all night maybe heavy condensation or is thers a leak and carpets permanently damp ?

Either of first 2, a pipe off as long as u can hear fan going

Promise the system works when u get used to it......unless u ve got a Cup CAR THEN NO HEAT AVAILABLE , 1 SPEED FAN AND ONLY 2 VENTS TO SCREEN !
 
Remove the 2nd disy cap! if the rota turns freely remove it. put the cap back on and run on 6 plugs. If your anywhere near us I am happy to have a look. Berny.
 
Both rotors are firm, i.e. neither is rotating freely. I should have worked that one out as a test - the second unit it belt drivem isn't it?

I'm not that close to Stowmarket but might be possible - Saturday morning?

Nick
 
This seems to be more of an intermittent problem - the car ran faultlessly for about 5 minutes earlier but then went back to misfiring badly (you can smell the unburnt fuel in the exhaust gases).

Something, somewhere is breaking down under temperature.

I've already swapped the DME relay for another unit but that didn't affect it.

Unfortunately, I also can't reach the folks who service it - not answering.

Nick
 
Aha - progress.

I managed to get the car into Autostrasse earlier and it seems likely that it's the engine wiring loom, which has not been replaced despite the recall Porsche placed on this 10+ years ago.

This would also explain the intermittent action of the engine oil temperature gauge (same loom).

It's a pain, but at least it looks like we might be onto the cause.

Nick
 

Hopefully you're getting somewhere with the mis-fire Nick, can't see why it would be the wiring loom problem but I bow to Autostrasse's greater knowledge.

The misting problem is water getting into the air intake at the rear. It might be my imagination but this seems to have got worse in mine over the near ten years of ownership. I really must take it apart and see if there's a blocked drain hole. It's only an issue after quite heavy rain, especially if being wind driven towards the engine cover.

If you turn the thermostat right down it's not a problem as it draws air from the fresh air vents at the front. There's no real work around if you want hot air but it can be improved by getting the car up to temperature, then putting the air flow to the footwells with the windows open a bit, turn the thermostat to max and the blower on. After a minute or so you can turn the air flow to screen and press the demist. You will still get a bit of misting but not too bad. I try to coincide it with being stopped at traffic lights just in case.

I'm also a bit confused by 996 turbo's comments. I had always thought that one distributor fired one of the plugs in each of the six cylinders and the other one fired the other six plugs, not one firing the left hand bank plugs and the other the right?

 
That's an interesting thought regarding the misting - it certainly is worse when the car's been standing in rain, which would argue that your theory is correct. Where is the air intake where the car picks up the warm air?

I too think there's one plug per cylinder per distributor. One bank not firing at all would give a very bad misfiring situation. Mine isn't great but it's more or less firing on all cylinders, just not very effiiciently.

The wiring loom problem could give the symptoms I'm seeing, especially considering the simultaneous failure of the ignition system and the oil temperature gauge. Intermittent or even low voltage to the ignition system would give problems, and it's a fairly safe bet that the engine-based sensors are mostly connected through the same loom too.

Anyway, I'm waiting for Porsche Colchester to confirm a date for the work and will report back.

I'll get it sorted eventually.

regards
Nick
 

ORIGINAL: nfearn

That's an interesting thought regarding the misting - it certainly is worse when the car's been standing in rain, which would argue that your theory is correct. Where is the air intake where the car picks up the warm air?
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The air intake is on the left hand side of the engine bay. The thing with the strange rubber netting on it.

My car's always garaged at night and I only get this issue slightly after I've washed it but quite badly if it's sitting in the work car park all day during heavy rain.

 
ORIGINAL: bernard tester

Hi get the loom done asap they have been the cause of engine fires.Berny.
Click to expand...

Absolutely. The car is not useable in its current state anyway (not that I would with the misfire) but it is being booked into Colchester as soon as they can take it, which I hope will be this week.

Regarding the air intake, mine's a non-varioram so doesn't have the mesh-covered intake. Can anyone advise where water could collect in the warm air system causing the misting issue?

regards
Nick
 
I dont think the car would even run on 3 cylinders would it?

One dizzy does all 6 pots top plug, the other dizzy does all 6 pots bottom plug
 

ORIGINAL: nfearn

Regarding the air intake, mine's a non-varioram so doesn't have the mesh-covered intake. Can anyone advise where water could collect in the warm air system causing the misting issue?
Click to expand...

Both are the same Nick. The intake sits on the far left hand side of the engine bay under the engine grill towards the back. It's black plastic and about four or five inches square with (normally) a rubber mesh or grill which forms a seal of sorts with the engine grill. Tried to attach a photo but it didn't work [:mad:]


 
Not sure if this helps but if you have the air conditioning on and it is set to interior air only after a while the car will mist up big time. If this happens turn back to exterior air and turn the fan onto max.
Peter
 
Nick that looks exactly like my early 94 MY 993. Air intake is from the engine fan shroud. I don't believe that is where your condensation is coming from. Condensation forms when warm damp air meets a cold surface. Have you checked the foam underlay under your carpets. If that is wet, then I believe that is the most likely source of your problem.

I agree wiring loom recall is key suspect for your electrical problem. It can produce some odd effects, and should be carried out free if charge.
 
ORIGINAL: MoC2SWho didn't read the 993 Buyer's guide .. [8|] .. just be careful that replacing the loom doesn't upset something else .. often something gets left off .. [8D]

Cabin hot air is drawn throught the ducts under the engine via the heat exchangers on the exhaust pipes - totally separate from the engine air intake.

Good luck - cheers, Maurice [:D]
Click to expand...

I read it but assessed the chance of the loom not having been done as relatively small. It had been on the to-do list to check it but this problem came up and prompted it.

I suspect the misting is due to water collecting somewhere near the heat-exchangers - it's not a major issue at the moment and something I can look at when I get more time. The cabin interior is bone dry - I've checked all around and there's no dampness anywhere, fortunately.

Nick
 
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