Hello everyone!

I'm having some mysterious issues with my car after the swap. I swapped everything, it has the GTI fuel pump, but still has a rough idle when cold, and poor perfomance even when the engine is at it's operation temp, and it cranks for 3-4, even 5 secs before it starts the engine.It struggles at higher rpms, and has a top speed of 150 km/h instead of 200 km/h. I replaced almost every sensor I could, it's definitely not the lambda sensor, or the crankshadt pos. sensor. Even replaced the coolant temp sensor. I noticed that I have a grey 167 fuel pump relay with 4 legs instead of a black 410 with 8 legs. The guy who made the wiring, didn't notice the different relay. Can this be the cause of my problem? Or could the VVT actuator failure cause this?

Thanks for the help!

Edited 29 December, 20187 yr by AkosSpekker

Assuming it was all fine before the swap... could the ignition timing be too retarded?

 

Or air leak at injector o-rings.

Edited 29 December, 20187 yr by dvderlm

13 hours ago, dvderlm said:

Assuming it was all fine before the swap... could the ignition timing be too retarded?

 

Or air leak at injector o-rings.

we've already checked the timing. We swapped over everything, except the relay. I mean could the fuel pump relay cause this? Maybe getting less voltage or something. When it was in the other car, it started perfectly, and had no problems at all.

Maybe. The relay either switches or it doesn't. If the high current contacts are worn, then less voltage to the pump.

Can you swap the relay for known good, or temporarily bridge the contacts? 

The "extra contacts" on the original relay are for the input from the airbag ecu to stop the pump in the event of the airbags being deployed, they are not used on the 6N1 setup so as long as the pump unit is receiving a good 12v supply and has a good ground.

23 hours ago, nige8021 said:

The "extra contacts" on the original relay are for the input from the airbag ecu to stop the pump in the event of the airbags being deployed, they are not used on the 6N1 setup so as long as the pump unit is receiving a good 12v supply and has a good ground.

I tried to swap the relays, but it just cranks but doesn't want to start. My other guess is really the VVT that could possibly cause this... It's definitely an electrical problem, but I can't find out what could cause symptoms like this...

Any fault codes stored and accessible?

The VVT only comes into action at higher rpm. Did you connect the diagnostic wiring ? as that might give you a clue as to what's going wrong ?  Here's a link to the wiring diagrams for the GTi engines http://s1117.photobucket.com/user/nige8021/library/Wiring Diagrams 2/ARC Wiring diagrams?sort=3&page=1

On 31/12/2018 at 15:05, nige8021 said:

The VVT only comes into action at higher rpm. Did you connect the diagnostic wiring ? as that might give you a clue as to what's going wrong ?  Here's a link to the wiring diagrams for the GTi engines http://s1117.photobucket.com/user/nige8021/library/Wiring Diagrams 2/ARC Wiring diagrams?sort=3&page=1

It didn't give me any fault, just the airbags and the rev counter, because my clock doesn't have can bus. But other than that, nothing. I had a vacuum leak fixed, so it couldn't be that. If it's warm, it runs fairly smooth until 3-4k rpms, then it starts to lose power. I noticed i have small backfires when it's cold, and it's very weak, and hard to keep it running. I couldn't hear the VVT turning on at higher rpms. 

Timing belt? is it the one that came with the engine?

If you replaced it its easy to be a tooth out and get poor running engine

On 05/01/2019 at 00:50, LR5V said:

Timing belt? is it the one that came with the engine?

If you replaced it its easy to be a tooth out and get poor running engine

We've already checked it, it's fine 😞 I guess it will be a fuel problem, maybe the pump doesn't get enough voltage...