John Speake

The LH and EZK are pretty dumb as far as the Temp 2 fault code. Code 1114 can be "open/short" - not very helpful.

But if you can read the temp values in real time with the tester , then that is perfect, no need to get a meter on there. What values do you read, cold and hot ?

the flyin' scotsman

Cold the T2 sensor reads 3.26k ohms.

I'm now wondering about the MAF again............if it hasn't changed then why does the OD measure ~3.7"?..............its been rebuilt as it has 'red' goop around the electrical piece. I could swap the MAFs between the S4 (rebuilt by JDS) and GT.

oups59

Good test to do. Easy and quick.

I never had a high idle problem when my MAF died (twice). My symptoms were a hunting idle than the engine dies.

Good luck.

John Speake

There's quite a spread of tolerance for the T2 sensor. But 3.26k from one side to ground suggest a temperature of ca 25degC.

MAF outside dia at ends is 3.75"

the flyin' scotsman

thx again John............I confirmed that the MAF on the S4 is same size, well over 3".

I measured the Temp 2 sensor as the engine warmed somewhat and the resistance fell very quickly to 600 ohms. Ambient is only 7c and the car is in an unheated garage..........the first reading was taken after the car was backed out the garage and engine shut off so was still quite cold. Given these readings it appears the sensor is reading lower resistances that WSM stated.

I'm about to rip the intake off again unless I get divine enlightenment.

the flyin' scotsman

Its all apart.............again.

Obvious issues are the throttle plate machanism is bent so I assume thats cause for a leak. The t.body gaskets are new so someone was in there recently. The hoses to/from the ISV are rock hard. The t.body is coated with a film of oil/gas.

Anyone offer a t.body rebuild exchange?

John Speake

OK, so you have some mechanical issues, hope you can get replacements at resonable cost.

When you measured temp 2, did you get those same low readings from each terminal of the sensor in turn to engine block ?

worf928

Yes.

More specifically, if the resistance through the Temp-II circuits is higher than it should be at idle, the ECUs will assume that it is cold outside and command a higher idle speed. Measuring resistance in a static no-load test with a MM will not always give you a good indication of the resistance through the circuit. Contact corrosion and/or a high-resistance ground path through the water-bridge can "fake out" the ECUs and convince them that it is -10°C out...

BTDT.

the flyin' scotsman

Yes, both terminals read the same low readings. Of interest, I read the cold measurement after backing the car out the garage and shutting the engine off. You obviously have to disconnect the T2 connector to read and I tried to restart it wouldn't run. Re-connect the T2 sensor and she fires right up.

As the car warmed I removed the connector again, engine running and it remained running........normal?

the flyin' scotsman

thx Dave

The readings taken show lower sensor resistances.

Is there another method to determine the circuit resistance..............measure the respective connector leads to ground? or both connector leads together?
I recognise each connector lead is connected to one of the ECUs.

Stromius

Yep engine will run but should 'notice' the disconnected Temp2. It should not start with it disconnected however.

John Speake

Disconnecting temp 2 at any time will result in the LH defaulting to the fuelling for an engine at full working temperature - a sort of get you home mode.

So if engine is cold, starting would be difficult and if disconencted when runing cold could result in a stall.

Once engine is up to temp, then unpluging (or a short circuit which triggers the same mode) won't make much apparent difference to the running of the engine.

the flyin' scotsman

I just measrued the T2 sensor again.............engine is stone cold, ambient has now warmed to a balmy +3c.

5.42k and 5.34k ohms respectively.

Stromius

Seems like that's in spec. @ Freezing it's supposed to be 4.4k to 6.0k Ohms and the next spec states 15 - 30 C / 59 - 86 F: 1.4k to 3.6k Ohms.

FYI only and maybe OT but I replaced my Temp2 yesterday via warranty with Autozone. P/N was different than listed but cross referenced to the porsche parts with help of their customer service. Correct AZ p/n was SU5817 and NOT TU358. Mine didn't spec out at the 15-30 range - was 330-350 hence false reading to brains. I would order from our big 3 but these preceeded my enlightenment

worf928

Resistance from the body of the senor to a ground point should be <1 Ohm. You can always belt-and-suspenders a test by using a direct ground lead from the sensor body to a ground point.

Otherwise.... dunno. An EE I'm not.