Multiple misfire after n75 removed and rplaced with MBC

[langmaier]

Put in my manual boost controller 3 days ago and ran it with no problems was hitting 17psi and holding to 15 at redline. Today car started shuddering and acting weird. Dis a scan with vagcom came up with these codes


17956-Boost Pressure Regulation Valve N75 open circuit.

16684-Random/Multiple cylinder misfire detected

16686-Cylinder 2 Misfire Detected

Now what im wondering is how do i fix this but keep the manual boost controller? Boost controller stopped my spikes completely and I dont wanna let it go unused.Jerbil im lookin at you for this one!! thanks.

[R-Audi]

Re: Multiple misfire after n75 removed and rplaced with MBC

You arent supposed to completely remove the N75, but run the MBC inline. Or I beleive you can loop it to itself and run the MBC by itself. Either way, if you dont have the N75 plugged in, you will throw the 17956 code.

If I were you I would have started with looking for the reason why you are spiking instead of throwing on a MBC as a bandaid. I dont think there is any current tuner that uses an MBC instead of the N75...

[Disturbo]

Re: Multiple misfire after n75 removed and rplaced with MBC

Plug the N75 back in and still use the mbc you have. The missfire would be a coil pack

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

I had heard of people rt inline. but the graphs i seen with the mbc looked much better across redline. i will now run it piggie now that its having hiccups. my coil packs only hav maybe 2000km on them but i do have several spares.What causes boost spikes to begin with?Also anyone running the ecs race N75 and having good results with it?

[The_Jerbel]

Re: Multiple misfire after n75 removed and rplaced with MBC

Plug in the N75 electrical connector but keep the MBC connected in standalone, then clear your fault codes. You should be all set.

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

Do you think the misfires are related to the boost controller in any way?Another thing I thought was weird, when I did the install on the controller I started tuning with the dial turned all the way down to nothing, and I still hit 14 psi..is there just a minimum boost level the car always hits or is my mbc just not worth the 50$ i paid?controller says good from 5-30 psi. Is it possible i have some of the hoses installed incorrectly?

[Disturbo]

Re: Multiple misfire after n75 removed and rplaced with MBC

Do you have a T so its going to both of the wastegates?

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

Ya it came with a fancy looking T. You can see it in the pic i attached to the last post. The T has one spot that i could not blow or suck air through, but so did the N75..so i just hooked that vacuum line up the same way. I just swapped out the cylinder 2 coli pack with one of my spares and hooked the lec connector back to the n7f but didnt touch the MBC(kept it standalone). So we will see tomorro on the way to work how she performs. Also I took out one of the spark plugs just to peep it, the thing was like a weird red colour? Am i running it too lean now...my tune is for 16 psi and im running 17-18 now with the mbc installed...i dont wanna pop that expensive motor...

[Disturbo]

Re: Multiple misfire after n75 removed and rplaced with MBC

In your pic the Arrows points in two directions thats your problem why its not working

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

What way should i have the vaccum lines then? This is my 1st turbo car I have evr worked on..The damn thing didnt come with any directions really like wtf. I am getting more boost than i was before running the controller tho..i have a tune for 16 but was hitting 12. Thats why i did the mbc plus to eliminate spikeyness.

[The_Jerbel]

Re: Multiple misfire after n75 removed and rplaced with MBC

Your WG's may very well be set to crack at 14 psi. What turbos are you running?

The driver's side and bottom side lines that come off the N75 should be hooked up to the MBC. The pass. side line should be left alone. Also leave the elec. connector attached to the N75. Other than that, the MBC should be set up correctly. The misfire could be attributed to the ECU not detecting the N75 sensor after you unplugged it, then it went into limp mode but the MBC was still allowing the car to make 16 psi (or whatever the boost pressure was). This could cause a misfire. I would just clear the codes, plug the N75 connector back in, and see how it runs.

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

Yep plugged in the n75 last night and also swapped cylinder 2's coil pack for a spare. No misfire no codes and car pulls hard. I only have the stock ko3's but they seem solid. No shaft play when I did the piggies felt super solid and free spinning. Stopped at a euro tuner shop here in regina and buddy said to order a diff controller, one that has a vent hole in it? Said im playing with fire with the one i have now...and that i could be running full boost on one turbo and only half on the other? His eyes lit up when i even told him I had a mbc. He was like '' really, and it works?'' lol

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

Whats the factory amount of vacuum pressure that my gauge should read at idle with all accesories off(air conditioning/heat?)

[R-Audi]

Re: Multiple misfire after n75 removed and rplaced with MBC

I still dont understand why you are even using a MBC. What programming are you using? Most arent designed to work with a MBC..and designed with the N75 in mind.. probably why he was shocked.

Most people see 18-20hg at idle...

[langmaier]

Re: Multiple misfire after n75 removed and rplaced with MBC

Im using the mbc to gain extra boost. If what jerbel is saying is accurate, my wastegates are set to blow at 14 psi...chris at das auto chipped my car with stage 1 thats supposed to run 16 psi...but it only hit 12 and hold at 10 along redline. Mbc gave me 17 and held to 15 at redline as well as deleted my boost spikes. So i guess its just a bandaid? But a damn good one! Car is running like a top.