944S sensor and oil/air seperator question

[Dunners]

I'm hoping someone could kindly point out and help me with a few items.

Recently my 944S hasn't being running 100%. I believe I've found the culprit to be a very bad connection to one of the knock sensors (the connection was basically falling apart). Having taken the inlet manifold off I checked a few other items whilst I was there and found this:

The sensor on top is the Crank Positioning Sensor, but could someone please clarify what the sensor is at the bottom? I only ask because the wire running from it leads to the second picture and is obviously not plugged in anywhere. The only place where it looks like it could be plugged into is the plug below with a (what looks to be) OEM makeshift 'plug end' already in it?


My second question is to do with oil consumption. Having taken the manifold off I've found the inner wall to be covered in (what looks to be) a very viscous/gooey film of oil. Is this normal due to the age of the car and the way the oil/air separator and vacuum lines are plumbed in, or do you think there is an issue somewhere else? Possibly the seals on the oil/air separator are gone? My oil consumption isn't horrific (well within Porsche recommendations), but at the same time is still a cause of slight concern. There seems to be no oil leaks anywhere and no blue smoke at high-revs. Valve stems should be good too due to a semi-recent head rebuild...

Any help with either would be gratefully appreciated.

Many thanks.

 

[bmnelsc]

Re sensors - Clarks Garage has an explanation - http://www.clarks-garage.com/shop-manual/ign-02.htm
Perhaps some modifications have been made? Do you have original ECU/chips?

 

[Dunners]

I've read that the 16v 944's only had one sensor with regards to that area. That's why I'm confused that there's two and that one is not connected to anything.

The car is completely standard. The DME hasn't been touched.

 

[bmnelsc]

I found a reference indicating that the S2 and 968 had only one sensor (this was a US car might be different for others) but the WSM makes no reference (that I have found) to only a single sensor. Even the photo's re clutch replacement clearly show 2 sensors in place.

Now I have to look at my S2 (ROW delivered to Japan) - I "thought" I saw 2 sensors there.....

 

[edh]

It's certainly not there on my S2 - only one sensor in the bellhousing.

 

[colin944]

I have similar issues with the air/oil separator and or the breather system on my S2. I'm going to replace the separator as I believe it is probably knackered after 25 years.

 

[zcacogp]

Hmmmm. My S2 has intermittent oil use, which I have posted about on here before. Essentially, sometimes it will use quite a lot of the stuff (300+ ml for a couple of hundred miles), sometimes it will use none at all for a thousand or more miles.

Several people have suggested the AOS, so I removed it and opened it up. It was simply a large, empty cannister - completely clean, with no more than a thin film of oil inside it, as you would expect given that it's the means by which you put oil into the engine. The seals looked OK, but I couldn't understand why they would be at all critical; if they failed, it would simply leak a bit of oil when you fill it up, nothing more. To be honest, I couldn't quite understand the purpose of it, although there must be one.

Anyway, I put it back in and nothing changed; the oil use has remained as intermittent as ever. So I'm confused.

OP - I hope you get your problems sorted out. And if you can post the solution to your AOS problems on here then I will read them with interest.


Oli.

 

[Dunners]

I've read it's all to do with 'poor vacuum in the crankcase' which is caused by dried up air/oil separator seals, cracked and broken hoses for the vent into the intake boot and dried up o-ring/seal on the oil filler cap.

I popped to see the ever helpful Andy at ProMax over the weekend. Thankfully he had the relative seals in stock so I set about getting them changed whilst everything was apart.

Taking the oil/air separator off, I had (what seemed to be) a bit of oily gooey 'mayonnaise' sitting at the bottom. I'm guessing this is the product of the part doing it's job?

The seals didn't look too bad either, however did look a bit flat when compared to the new ones. Anyway, everything was cleaned and reassembled so I'm hoping this will do the trick (touch wood)!

Another sensor question? Anybody know what this sensor is? Sorry the picture isn't very clear, but the sensor sits on the intake manifold just in front of the throttle body. Interested to hear if S2's or Turbo's have anything similar?

There is a tube (not connected in the pic) leading from it to the back of the oil filler tube and throttle body and it too was also clogged up with oily mayonnaise. I'm curious to what the actual sensor does, as I'm sure it's all interconnected with the oil/air separator some how... And I'm sure it being blocked as well obviously wouldn't be helping matters.

 

[Hallsy]

As above, I believe when the AOS seals are leaking it will effect vacuum.

I had similar gunge in my inlet when I stripped down my 944S intake - I had a stumbling idle and intermittent stalling so stripped it all down to look for vacuum leaks.

I cleaned the inlet out as best I could, as well as the TB, etc and replaced any suspect vacuum connectors whilst there as many can only be accessed with plenum off. Also worth correctly adjusting the TB throttle stop and idle/full throttle switch.

My AOS was full of mayo type gunk and the seals had been leaking so I stripped the AOS down and cleaned it out and replaced the seals.

All of this sorted the stalling issue and general stop/start throttle response, although I still had a slightly uneven idle - but I don't remember my S using much, if any oil. I used to use Shell Helix 10w-40.

Here are some pics from when I cleaned it all out:

http://forums.tipec.net/viewtopic.php?f=25&t=13151&p=121301&hilit=AOS#p121301

 

[Dunners]

Thanks for the reply Hallsy, much appreciated.

I've put everything back together today and took the car for a drive. Not sure whether anything has improved or not as the car seems to be driving exactly the same. Like you (whilst everything was apart) I tested the AFM and the TPS sensor - all checked out ok using the Clarks Garage help guide... The only thing I stupidly didn't check was the electrical readings for the knock sensors. However, I was hoping/convinced it was the top connection that had gone due to cracked wires and it basically falling apart!
As you own a 944S (and this is the first one I've driven) can you give me an impression/description of how it drives with regards to throttle response? My car seems very hesitant (especially at low revs and bogs down) when applying the throttle which can only be described as something similar to turbo lag. The response of the engine always seems like it needs to catch up with the position of the accelerator pedal. Is this similar to your car or any other 944S owner who is reading this? I know the intake manifold is crap on the "˜S' (in terms of its design), and I know they are not renowned for their low down torque, but I didn't expect it to be this bad.
For reference, this is the work I've carried out so far:

*Changed spark plugs/dizzy cap/rotor arm. HT leads seem to have been changed at some point, so I don't think I need to change them.
*Changed electrical connection to the second knock sensor.
*Changed the track position within the AFM and check electrical readings (all OK)
*Checked the condition of the TSP (throttle positioning sensor) and electrical readings (all OK)
*Cleaned and checked all vacuum lines.
*Changed seals for the Oil/Air separator and cleaned out all the relative bits along with any pipes that are associated with it.

Again, any feedback/further help will be greatly appreciated.

 

[Hallsy]

Hi Dunners - I sold my 944S back in October last year, but I would say mine was similar to how you describe.

I only really noticed it when pulling away and in stop/start traffic - exactly as you describe, like it bogged down a little at low revs. Once on the open road, and through 5k rpm it pulled very nicely. Mine had a Promax chip fitted which a previous owner said improved the engine response.

But realistically, once on the move I felt the response was good, as long as you were in the correct gear - it really did like to rev out.

Other things to check with your problem:
ISV - should have checked while inlet was out really, but is your idle OK
Cam position sensor - the connector for these are prone to failing on the S - check the condition. Engine will still run OK with faulty cam sensor, but not as well as it should

Otherwise - a smoke test may help to reveal any vac leaks you have missed.

On another note - make sure that the cam chain tensioner pads are in good order, any doubt and replace them. You can get top & bottom pads from OPC for around £65 iirc.

 

[Waylander]

If the 944S has a Cam Position sensor (Hall Sensor) I replaced mine on my 68 for £13.00 you need an HKZ101 sensor. use your old plate rewire it.

Hall Sensor

http://www.hallsensors.de/Hall-Vane.htm

 

[Hallsy]

It does - suspect it's the same sensor.

 

[Waylander]

the sensor from OPC is £190.00

944 606 170 02

 

[Dunners]

Thanks for the reply chaps.

Checked the condition of the Hall sensor yesterday as recommended. Funnily enough it too had a connector that was falling apart with exposed wires... Popped to ProMax again and picked up a good second hand item and spliced the wires. Unfortunately absolutely no change.
I'm really at a loss now - ever since I've carried out a service and changed a few items the car seems to be running worse! The car starts from cold on the button and once up to temperature idles beautifully. It's only at it's worst when driving in the lower rev-range. Once above 4-5k (as said) it starts to pull nicely although there is that lack of throttle response with a few flat spots.

The car has had a recent head replacement so the pads/cam chain are new. The idle control valve was also replaced with a good known working item. The temperature sensor has been replaced recently too.

The only items I haven't checked yet are to do with fuelling. I'm trying to get a hold of a fuel pressure gauge to measure what's happening at the fuel rail. The fuel pressure regulator looks to be original, so it could be the answer to my troubles... However, I can't see how with the adjustments I've made and the parts I've replaced would make the car run bloody worse than it was and lead to something faulty with fuelling?

 

[Hallsy]

I have a fuel pressure gauge with suitable fitting if you'd like to borrow it?

I did the same tests on my S and was bang on spec according to the Clarks garage figures.

 

[Dunners]

Many thanks for the offer Hallsy. I guess it depends on where you are in the country?

They're not that expensive to buy, but it seems silly just to buy one for a single job. The thing is, I don't think it's fuel related. The car had been running 'alright', just a bit rich in my opinion. I think I've done something recently with things I've adjusted/changed that has caused it to run poorly.

 

[Hallsy]

I could post it to you at cost - up to you.

As you have had inlet off, etc - you are sure tps is set correctly and afm I'm, but did you make sure throttle stop was set correctly?

Also - I would try to get a vacuum gauge installed to see whether your vacuum is good, you may have accidentally cause a vac leak trying to fix one - although I would say this would probably cause an idle issue.

My S had had the injectors cleaned at around 100k, so something else to consider.

Only other thing I always wanted to try with my S was a system adaptation - but it needs a Bosch Hammer to do it I believe. I made a diagnostic lead and tried to use PIWIS to run the adaptation, it connected, but the S ecu was not an option so I selected a 964 ecu which was same type but it gave an error.

There is another tool you can use for the 16v ecu's, think it's called a JDS Spanner, but it was too expensive for me to try just to cure a slightly uneven idle!!

If you have a good local Indy they may be able to try a system adaptation, but continue checking the basics first.

 

[zcacogp]

Drew,

Poor running at low revs but OK when hot suggests that the fuelling and electrical side are in good shape. I'd be looking at sensors, as you are, but also suspecting the AFM and whatever advances the ignition. When you say that the AFM checks out as per Clarks guide, have you had it apart and inspected the tracks? Swapping parts to try is poor diagnostics, but if someone close(ish) to you has an S then it may be worth spending an afternoon together.

Unless, as has been suggested, poor response low in the rev range is simply a trait of that engine. The S's were always meant to be fizzy machines that needed to be kept on the boil to make progress. Is it simply this?


Oli.

 

[Dunners]

The only item I have mucked about with in any great length is the AFM. Having done a bit of research online, it looked to be the most common part that went wrong based on my car's running symptoms.

Upon inspection, sections of the original track had completely worn away. I therefore adjusted the pin so that it was running on a fresh line and continued to check the electrical readings. The results were as per Clarks Garage with no abnormalities, whether the barn door was fully closed or fully open. I also checked thoroughly that there where no fluctuations/spikes throughout the barn door's movement.

If the AFM was faulty originally and now is operating correctly, would this now effect something else along the line? The only item I didn't check in any great length, as you say Hallsy, is the TPS and the 'throttle stop'. I'm not 100% what you mean by this, but again, I checked the electrical readings whilst this was still attached to the throttle body and it too checked out all ok as per Clarks Garage.

I think it may be time to let Andy at ProMax have a look. I'm a bit pissed off to be honest as I really don't want to spend anymore money on the car. But unfortunately I don't know anybody who has all the relative parts laying around so that I can rule things out one by one.

I love these cars to bits, but some days it really does get to me! It's uncanny how you fix one thing and two weeks later something else goes wrong or breaks as a result of fixing the original problem. I've had as many problems with this car as I did with my Turbo (although that was driven in a more spirited manner). She's still missed to this day though:

I thought the NA cars were supposed to be more reliable!?