ca993twin

Every once in a long while, Rufus still throws an 1140 CEL code (improbable load sensor). While watching the OBD scanner, with the engine at idle, the TPS read-out was mostly 0.0%. But every once in a while, it would briefly show 0.39%, then go back to 0.0. I seem to get the CEL when I am coasting or using very, very light throttle. Does this sound like the cause and affect? And does this sound like a new TPS should fix this? And how much is a TPS, anyway?

Thanks for any advice.

Jussi

I'm not 100% sure if your TP sensor is broken. Because it can also be the MAF...
This TPS value is already a calculated value in OBD, so it is not only absolute TP value.
I noticed that when datalogging my MAF values, every time when the MAF went over its range, also TPS and Calculated Load dropped to zero or near to zero..
see my datalogging:
993TT datalogging

But you can check your TP sensor this way:
Turn only power on (don't turn engine on)
Plug your OBD reader on.
Now your TPS should be 0%,
then press the throttle fully down and see that TPS value, it should be something between 70-80 (like I had 78%)
and when pressing throttle, its value should smootly change between these limit values.

ca993twin

js-911,

Thanks for the great advice. The reason that I'm not jumping right on a new MAF, is that I recently replaced mine with a good working unit from a car with very low miles. It did not alter the issue I was chasing at the time, so I'm guessing there was nothing wrong with my original MAF. But... I could be wrong, and the CEL is quite infrequent. I'll have the mecahnic try the trick you mentioned with the ignition on, but the engine not running.

Maybe I'll call Sunset, and see how much the TPS is... if real cheap (hahaha), I don't mind tossing it at the problem.

ca993twin

Ok... the problem MUST be with the MAF. How do I know? I called Sunset Imports to ask pricing:

TPS.... $100.22
MAF.... $570.58

Perhaps I'll slip the old MAF electronics back into the original housing when we have the OBD scanner hooked up.

Jussi

TPS is easy to test with that instruction I gave. Did you already check its readings?
It is good to check max % value because you could have a loosen TP cable and the TP valve cannot open fully - this was the problem I had (66% with pedal vs 78% with lever).

Plug OBD reader and
check max TPS % value when you press throttle pedal fully down and
then turn the TP lever from engine department and check if you can get higher value.
If yes, you have also loosen cable but it can be tightened under the throttle pedal system..

You can also check your MAF functionality with OBD reader.
It should give about 10 g/s reading when idle and
when acceleration hard it should smoothly go up to 400 g/s - depending on the engine's tuning stage

911/Q45

Steve is still at the public library trying to check out an OBD2 reader from the children's librarian!

ca993twin

"Steve is still at the public library trying to check out an OBD2 reader from the children's librarian!"


Don,

OUCH! If I didn't know you better, I'd be miffed. Let me add... the children's librarian is a really hot chick.

ScottMellor

I just gersnorted a booger onto my keyboard!

ca993twin

Well, I happen to have my original MAF, so I thought I'd swap the electronics and see if there was any difference. The electronice are held in with 2 screws... only the screw head is designed to not be removed. So that leads to a couple of fascinating questions:
1). why do you suppose Porsche designed the screws to prevent the removal of the electronics? Are they trying to sell more stuff, or are the electronic somehow calibrated to the housings?
2). how the hell do you get those damn screws out?

Again, your help ... minus the boogers... is always appreciated.

Jussi

I have talked with Bosch experts about these Mass-Air Meters..
Guy there said that DON'T open screws and if you do, you'll spoil the Meter immediately.
The Electronics parts is very accurately calibrated to its own housing.
And if you open screws, opposite hole of screw are oversized and then the electronic part are free to turn...

btw. I asked also bigger MAF from Bosch and he promise to seek one for me.
He suggested also to use two MAFs, like in other superperformance car for example in Ferrari do that.
Then these two MAF signals can be combined with custom electronic and scaled to fit with Motronic but that's the another story

TB993tt

I'm afraid this is just talk IMO, 10 years ago Gunther Mandl used a twin MAF "solution" to produce the 600hp TTP 993tt -you can just about read it it the excert below:

If you read the bottom of the red column you will see the 600hp car actually performed like a 520hp car (which was actually confirmed by RS when they put a customers 600hp TTP engine on the engine dyno)

It is managing heat which is the key to power on the 993tt, this comes into play way before any MAF restrictions.

Jussi

little off topic but.. my problem really is too big airflow - not heat,
stock 993TT MAF just can't measure over 420 g/s values. You can ask this simple fact from any expert, like RS, Kevin, Jean etc. This is written into ECU MAF mapping table. Max value there is 5V @ 1545.8kg/h.
My new stock MAF gives illegal volts, +5.5V, already at 5000 RPMs and that confuses the Motronic..
Heat may become also problem in hot summer day at race track but not now..

TB993tt

way too technical for me

But.....I was merely pointing out that a pretty good tuner overcame the single MAF restriction by using two and his 600hp was still only as much real hp as is available from one MAF -hence my simpleton mind says that there is more to it than you think ?

Jussi

yes you are right,
but as we know, these so called "600 horses or +" are whatever they claim but maybe that is the main reason why your "only 520hp" monster beats almost every "superpower/+550/+600 etc" 993TTs and CGTs - your power is stone proof fact !

TB993tt

The 600 horses for the TTP car were verified by the TUV on TTP's chassis dyno -this is one for the chassis dyno "power run" versus engine dyno fixed load load debate where part of the 600 herd seem to disappear when the motor is held under load -this is an ongoing (and very interesting) subject

My car at 520hp was only as quick as many other 520-540hp 993tt's eg Bill S's, JJayB's ( ) etc
Comparing with CGT is a bit of a red herring since the power curve of the CGT means it has less area under the curve than even a 520hp Motronic boost control 993tt.
It is going over the 550hp real hp mark that takes the $$$ and expertise on these cars -going over 600 needs the special inlet and Secan intercooler and regular engine rebuilds since real 600+hp has the habit of stretching your metal

Please don't take any of my posts as negative, it is great to share your project and thoughts