pcmhacking.net

Now that VL400 has pointed out what the problem was, the changes make sense to me.
I've put the engine into a vehicle that in its current trim would easily weigh 350kgs more then the Commodore it came out of, not to mention, it has the aerodynamics of a brick. Of course you're going to have to bury your right foot deeper to accelerate at the same rate, so higher TPS vs RPM.

Dave001 wrote:Now that VL400 has pointed out what the problem was, the changes make sense to me.
I've put the engine into a vehicle that in its current trim would easily weigh 350kgs more then the Commodore it came out of, not to mention, it has the aerodynamics of a brick. Of course you're going to have to bury your right foot deeper to accelerate at the same rate, so higher TPS vs RPM.

yes, but then just driving up a steep hill would do the same in all cars if that was the case.

You have masked the real problem for sure.
What it's doing is checking TPS value at the current RPM and comparing it to the table, when the MAP value is within the set limits. If it's way off the table expected value it throws a code.

So have a look at where you have set the table. 1200RPM is set to 33% TPS. That's 1/3 throttle opening. The maximum MAP I guess you have set to 50KPa.

So in other words, your telling it at 1200RPM (virtually idle) and 50KPa MAP (or even less!), you expect the throttle to be open a third.
In reality you would see 100KPa MAP with much much less than a third throttle at 1200RPM, unless the throttle body was incredibly small (in which case it would probably run out of flow capacity at 2500RPM and you would essentially have an engine that wouldn't rev over 2500, but we both know that's not the case).
This is why the table was set much less. You have masked the problem

The reason there is a MAP limit and you don't want it checking the code at high MAP is because it no longer means anything. Think about it. At 1000RPM you could have 20, 50, 75 or 100% throttle. All would give 100KPA MAP. So there is no way to know if the current TPS value is correct.

Remember. When you take off from idle, the car doesn't accelerate any faster or make any more power with 50% or 100% throttle until you reach the point that 50% throttle no longer allows 100KPA MAP, then MAP starts dropping and power levels off where as 100% throttle would continue making power.
IE. Imagine a drag race between 2 identical cars, one at half throttle and one at full. The 50% TPS car goes the same speed as the 100% TPS car for the first few seconds, then levels off once the throttle starts restricting it and the 100% TPS car keeps getting faster.

good explanation!

ditto

I want to know what the real problem/cause is...

that plastic coupling cap on the shaft that couples to the TPS maybe?

OK so where can the fault actually be then?

I've tested all the wiring. I've tested 2 different ECU's, and tried 3 TPS's.

C14 has 5.01v coming out of the ECU feeding the TPS and MAP Sensor, I see 4.91v at the TPS, and the MAP sensor is reading correctly, so we can pretty much rule out there being a problem with that 5v feed.
C13 has 1.4v feeding into the ECU at idle, with 1.33v at the TPS, and has 3.91v at the ECU at WOT, with 3.93v at the TPS .
The Earth is also used for the CTS, which is reading correctly, so we can pretty much rule out it being a bad earth.
Of course these numbers are different to standard 808/082 because it's running through an Ecotec TPS, which has been reversed wired.
Buick TPS range 1.16k Ohms - 6.16k Ohms.
Ecotec TPS Range 1.57k Ohms - 8.25k Ohms
I was only seeing 70% TPS in Tuner Pro, so had to change "TPS Full travel - Worst case minimum voltage" to 2.59v to reach 98%

So now showing in Tuner Pro I have.
TPS 0% 1.35v
TPS 10% 1.64v
TPS 20% - 1.87v
TPS 30% - 2.18v
TPS 40% - 2.42v
TPS 50% - 2.69v
TPS 60% - 2.94v
TPS 70% - 3.22v
TPS 80% - 3.45v
TPS 90% - 3.72v
TPS 98% -3.90v

Looking at that it seems pretty linear, but I did notice when cranking on the throttle by hand, what I would call 1/4 throttle is showing around 37.5% TPS in Tuner Pro, I don't have another Ecotec or Buick here at the moment to check if that's normal.

So at the end of the day, that's what the ECU is being fed, there is nothing I can do to change that. I have to work within those parameters and change the settings/tune to suit.

Have you actually physically measured the voltage with a meter to confirm if its really reading like this?

could be a faulty ADC on the ECU if the wiring, voltages and TPS all check out. Those voltage ranges are way too narrow to be normal.

As vlad said check the plastic cup on the end of the throttle shaft hasn't gone missing. Very easy to drop and loose it with the TPS off. And if it was gone would cause a narrow voltage range.

If you don't know the plastic thing we're talking about then I'll almost bet it's the problem, because you wouldn't of even noticed it.

vlad01 wrote:Have you actually physically measured the voltage with a meter to confirm if its really reading like this?

Have you even bothered to read my replies, how did you think I was reading the voltages at the ECU/TPS switch, of course I was using a multimeter.

vlad01 wrote:could be a faulty ADC on the ECU if the wiring, voltages and TPS all check out. Those voltage ranges are way too narrow to be normal.

Again, have you read my replies, I've tested with TWO ECU's.

pman92 wrote:As vlad said check the plastic cup on the end of the throttle shaft hasn't gone missing. Very easy to drop and loose it with the TPS off. And if it was gone would cause a narrow voltage range.

If you don't know the plastic thing we're talking about then I'll almost bet it's the problem, because you wouldn't of even noticed it.

Yer mate the cup is in place. Not my first time fitting a TPS to a Holden.


You guys seem to be missing the point, I have an Ecotec TPS running on an 082 ECU, this is the incorrect TPS for the ECU, so of course you will see incorrect voltages being fed to the ECU from the TPS.

As a test to help explain this better, I just connected the MULTIMETER to pins C13 and D2 of the ECU.
With the standard Buick TPS I see around 0.4v at Idle - 4.05v at WOT, of course this is with the TPS sitting in my hand, guessing the idle point. As it turns the opposite way to a Ecotec TPS, I can't test it on the throttle body.
With the Ecotec TPS I see 1.3v at idle - 3.95v at WOT.

As you can see, everything is functioning correctly with the stock Buick TPS, but since I can't actually run the Buick TPS, I have to run the Ecotec TPS, and work around the narrow voltages it outputs.

As far as seeing a higher TPS% then you would expect at the actual throttle position goes, I suspect that the TPS resistance is not linear, and as such the narrower voltage sweep is perhaps throwing the % off, just a guess. That really doesn't matter though, I have a certain set of parameters to work with, and I will have to modify the tune to suit.

Anyway, everything seems to be working fine after I made VL400's recommended changes, no more errors being logged, and after a few VE map changes, the wide band logs are looking pretty good.