UKKid35

Here's my job for today




Interestingly the Throttle Switch claims to be made in Germany, but the Knock Sensors are made in Romania

Prices seemed very reasonable, at £52 and £22 x 2, p&p inc

Hopefully this will regain me some lost power, as the car is currently struggling to get over 150

I haven't put a JDS tester on the car to check for faulty sensors, so it could still be a faulty Hall Sensor

However at those prices it seemed the right thing to do, as the last time I changed a knock sensor was about 15 years ago

Fuel injectors have all been cleaned, so I'm struggling to think of another possible cause of the power loss, not that the car feels slow, but objectively it is

John Speake

Hi Paul, I think I checked out your MAF ?

FredR

The throttle switch full open contact tells the LH brain to go full enrichment for power and the max power ignition advance maps. If that contact is not working you will lose some top end but checking that contact for function is very easy. You clearly understand the function of the sensors and the Hall trigger and changing those elements out pre-emptively is never a bad thing. Thus if you are going to pull the inlet manifold might as well do the things captive to that operation. The Hall trigger is a separate activity.

Having a tool to check the operation of these things is a bit of a must have- I use my ST2 in that regard.

UKKid35

"I've tested it and it is only 0.9% low on spec."

That was about two years ago, perhaps 8k miles, so presumably still OK?

UKKid35

Yes but I don't trust components to work the same when you test them, as under real world conditions with high under bonnet temps

I am hoping that the switch is at fault, as I was foolish enough (and money was tight) to fit a used switch just 12 months ago

dr bob

FredR

Another reason why ST2 is very useful as one can monitor in real time what is working [or not] on the engine. I have always opined that the flappy should have an indication whether it is working. For a while I ran with a vac gauge on the HVAC vac system to test whether the vacuum was holding up over a run [it was]. If the vacuum holds then it is a fair bet the flappy will be operational. Still some kind of position indication to give positive feedback of the thing would be a useful addition over and above the buttometer that has been known to let me down.

StratfordShark

FredR

That just tells you it is working when you start up and is a two man operation type of thing.

What I feel might have been warranted in the original build is some kind of real time direct indication that the vac system is viable and that the flappy operation is in play and responding- something like the PSD lamp but direct feedback from the shaft movement.

StratfordShark

Sure it's not a perfect test, but if it works on start-up (and that's quite demanding, as relies on vac reservoir being ok) then I can't think of any likely circumstances which would stop it working at 4000rpm, since the LH will send the same signal at 4000rpm that it sends for the test cycle. You'd convince me if there were some experiences of the system working on test, but failing in 'real world' (but I also take your point Fred that it's hard to be sure it works in real world other than using the seat of the pants test gear!). I have faith that Porsche engineers would not have included that test if they didn't think it would be a reliable test of the system, but this all becomes philosophical.

At least if it fails on test, it's never going to work at the real trigger point, so you'd learn something valuable in that case.

Mrmerlin

I would also suggest to replace the flappy and throttle shaft bearings,
adding new seals will reduce false air and prevent the new TPS from filling up with oil.

I am doing an intake refresh and i took the TPS off and it had oil in the connector pin area.
I sat it on a table in the sun with the shaft opening down and left it for a few hours,
when I came back a large stream of oil had run out of the TPS unit.
I put the new double sealed shaft bearings in

UKKid35

Sadly I had to retire the car from the exquisitely expensive double track day at the Ring when the rack blew its seals on the first day




I did a handful of laps in the morning once the track had had dried out and really enjoyed it with the car working brilliantly

Best not to work out the cost per lap though

The car is no longer struggling to pass 150 and was doing so on Dottinger Hohe

On the way home I did a half hearted V Max and achieved 164 but backed out while the car was still accelerating

It wouldn't have been a proper test as the sunroof was open and the headlights were up



I wasn't even breaking the law as I was on the derestricted #1 Autobahn at 2am with virtually no traffic

I don't think it was necessarily the Knock Sensors that were the problem, as the old ones looked in great condition

Instead I think it was the Throttle Position Switch - of course it could have been both

Also worth mentioning that this car has over 238k miles on the clock and is probably worthless as a result

That hardly matters as I will never sell it