I've got a small problem which i need your opinion on. My 24 years old original emissions harness is toast so i built a new one. I left all those air pump and solenoid valve connectors out of the new harness because that stuff left my car some months ago.

Here comes my only problem so far: I can start the car but i can't accelerate. Everytime i try to rev the engine up it stalls immediately. It also idles a bit rough and it's running very lean.

I allready checked all the connections to the sensors. No mistakes in my wiring harness. The TPS is brand new and working. I'm using an emanage blue with al harnesses to control my injectors and ignition timing and so on. I also checked the emanage harnesses for mistakes but found nothing. I logged the afm output with my emanage and that seems to be ok, too. There's 14V on all 4 injector wires connected to the ecu when the engine is running so they should work, too.


The only reason for my problem i can think of would be that i mixed up the injector connectors so that the two primary injector signals are firing 2 injectors for the same rotor but i'm not sure if that really would cause such a problem.

 

im gonna assume your new harness is the problem. ohm out the connectors from one end to the other and see if your getting continuity at the right wires

 

As i allready wrote i checked all the sensor connectors and the injector connectors and they are all ok. My emanage gets good signals from the tps and the afm, too.

 

series 4 or 5? did you delete the OMP?

 

Series 4. The omp is still there and working.

 

probably a ground issue. you sure you grounded the harness securely?

 

I'm going to check that tomorrow. The new harness is grounded near the ecu. Maybe i should add a ground on the other end of the harness, too.

 

You can quickly shove another wire into the back of the TPS plug which houses the ground wire and ground the other end to the engine housing and see if that helps narrow down your problem.

You can also backprobe the injector trigger wires at the ECU, namely for the two primary injectors, and see what the voltage reading drops to as this will tell you something as you should absolutely not have 14 volts on the injector wires at the ECU for if they have high voltage then they cannot fire for they rely on a ground signal from the ECU so 14 volts w/engine running should only hold true for the secondaries for they wouldn't be working at idle or not under load, but the primaries should have far less than this 14 volt reading.

 

Today i added a ground at the other end of my harness and now the car is running better than ever before. The resistance between the map sensor and the other ground was simply too high. I can't thank you enough for your suggestions.

 

no thank you for this question cause i would've asked it in a couple of days. Any tips on tackling this project for a first timer (I will have supervision from my dad who is an electrical engineer)? btw how do you like the e-mange you're running?

 

and the car is an S5 turbo

 

I got a second harness because i didn't want to cut my original harness down in case my new one wouldn't work. I wasn't able to get new pins for the ecu connectors so i started removing the pins from the connectors of my spare harness, cleaned them and soldered them to my new wires. Ugly work. I took all the pin housings from my spare harness, too.
Best tip ever: test your work by measuring the connections because it's a horrible task to find a mistake when the harness is wrapped and inside the car.

The emanage is a nice tool as long as you don't want a high end tuned car because it can't remove the afm. The software is nice and easy to use and you can do almost everything with it a standalone system could do.