How to test throttle position sensor

[nycplumber]

I'm not making full boost on my harrop kit and they mentioned it could possibly be the TPS. Does anyone know how to test this? Thanks

[CamasM3e93]

I think they are referring to the oem sensor on the s65, and the Harrop ecu gets that data from one of the wiring leads in the car’s ecu box. The sensor looks like this photo below. There’s one at the end of each throttle actuator bank. I think you will recognize the hexagon shape. Would review the live data (what the car thinks it is) and if the data looks feasible and no codes, recheck your wiring connections back in the box. Those are pretty tenuous and some shops take shortcuts and use wiring connectors that cause problems down the road.

[nycplumber]

Yes that is exactly what they're referring to. On older bmws you would hear an audible click. And on other cars you can test with a multi meter. I am just not sure of the exact procedure for this one. On our cars there is 2, one for each bank and while they're not expensive I don't like just throwing parts at things. Harrop is surprisingly not good at diagnosising issues with their systems.

[CamasM3e93]

Originally Posted by nycplumber

Yes that is exactly what they're referring to. On older bmws you would hear an audible click. And on other cars you can test with a multi meter. I am just not sure of the exact procedure for this one. On our cars there is 2, one for each bank and while they're not expensive I don't like just throwing parts at things. Harrop is surprisingly not good at diagnosising issues with their systems.

If the issue was the sensor the car would very likely throw a code. That’s what makes me think it’s the signal from the sensor not getting to the Harrop. Have you inspected the wiring splices in the car’s ecu box that provide the data to the Harrop mini-ecu?

[nycplumber]

That's the same thing I said to them about a vacuum leak they told me to check for. Yes I checked the splices. The car isn't making full boost in the lowers gears and builds like a centri in the higher gears so in my opinion it's not TPS related but I wanted to double check

[CamasM3e93]

Originally Posted by nycplumber

That's the same thing I said to them about a vacuum leak they told me to check for. Yes I checked the splices. The car isn't making full boost in the lowers gears and builds like a centri in the higher gears so in my opinion it's not TPS related but I wanted to double check

Sounds like your car runs like mine did. Have you completed any runs with traction control completely off? My experience is that the car cuts throttle during acceleration in lower gears when it senses wheel slip. The traction control doesn’t flash unless it’s particularly severe but the effect on throttle is enough to stutter acceleration and reduce boost buildup. I think in the early posts on the bpm harrop thread Mike suggests that running traction control off is really required to get the full effect. In higher gears (4th and up for me), I never ran into the issue. If that’s what is going on for you, when the car ecu cuts throttle the harrop ecu will open the bypass/blowoff valve wide open. But as the car settles in on higher gears the bypass valve will close and the boost will build rapidly. An experiment would be to take a few freeway pulls with TC off. A faulty wheel speed sensor also comes into mind but I have a hard time explaining the observation that the car builds boost differently in higher gears. But that’s not off the table. That seems to be a repair popping up in the threads on our 10+ to 15 year old cars.

A boost leak like from a folded over throttle body boot doesn’t seem to fit here. But I’m impressed how easy it is to install the SC head unit with that condition and never know. My shop did it to me most recently and I ran that way for close to a year until I uninstalled it for sale. Even inspecting each boot with a borescope you can miss it (my case). Anyhoo, happy thanksgiving. Hope you figure it out!

[nycplumber]

Just to make sure I'm not an idiot I triple checked and it's unfortunately not traction related. Consistently hits 3 psi gears 1-3 and then will build upto 6psi in 4th and then stays there all the way until I let off. It's also shooting from 3psi to 6psi when I let off the throttle in the lower gears. Very strange. Happy holidays!

[Bakerboy]

Originally Posted by nycplumber

Just to make sure I'm not an idiot I triple checked and it's unfortunately not traction related. Consistently hits 3 psi gears 1-3 and then will build upto 6psi in 4th and then stays there all the way until I let off. It's also shooting from 3psi to 6psi when I let off the throttle in the lower gears. Very strange. Happy holidays!

Get someone to go full throttle with ignition on but not running and push the boost rod with your finger under bonnet on the bypass to ensure it going all the way.

I had similar problem and bypass controller was fecked!

[nycplumber]

I did test this a few times and it seemed to be working. I was planning on putting the car on a dyno to test under load. But since winter is here I'll just mail it out since I'm not driving the car anyway. Whatever it is I hope it's helpful to the next person who has this issue because it's quite annoying lol.

[nycplumber]

Just a little update. I sent out my bypass valve to harrop and they confirmed that they "found sporadic operation of the motor" so this is good news and will hopefully fix my issue.