Hi there, I have recently purchased a 2000 audi a4 b5 1.8T that has had an engine swap and currently has an 1999 AEB 1.8T engine in it. It appears that the previous owner who did the motor swap kept the original ecu (8D0 907 557 P) and wiring harnesses from the original engine, and I'm pretty sure they are not compatible. Since the AEB engine has less components than the ATW (the engine that originally came with the car), so there are three wires that do not connect to anything, for example, the AEB engine doesn't have a secondary air injector, so the plug in and wires just lay in the engine bay. I have had a reoccurring problem that feels almost like a misfire. It only happens when i floor the gas, like under full boost. It also only appears to happen when I am trying to pick up speed quickly by using the turbo. It progressively leads up to what feels like a misfire, and you can almost feel it coming before it happens, like lack of power. It feels like the engine surges and starts to feel like an automatic rifle under the hood until I let go of the gas.

Checked codes:
P1422- secondary air injector (this code is on because the engine doesn't have the air injector to plug the sensor into)
P1287-Turbocharger bypass valve open

I have replaced:
the PCV
Multiple check valves
Spark plugs
Pressure Regulating Valve

I have checked:
MAF sensor (tested to see if it reacts to change in rpms, and did)

Need to check still:
Fuel filter

I'm not sure what to check next besides changing the fuel filter. I do have a boost gauge and it likes to stay in the 10-15 in the vacuum side until the turbo kicks in, and it runs about 6 psi consistently. And the car feels as though it runs a ton better when cold, but once it gets toasty, it likes to do that misfire thing if I try to get on it.

Thank you for the help

 

The vacuum seems way too low. I'm not sure if there is a difference between a chipped a4 and stock in the vacuum but mine is at 22 under idle, 10-15 seems low. Cold start will have a lower vacuum until warm. You might be looking at a boost leak, have you tested for leaks?

 

Whoa, running that P box and harness is a no-no. The pedal assembly is drive by wire. What throttle does it have in there?

Running that engine is not a big deal at all, but you need to get the proper ECU and harness in there. It is possible to swap an AEB ECU and harness into a 2000, but I highly doubt it was done correctly. Please provide pics of the engine bay

 

+1 My Vacuum stays around 25.

+1 It might be worth looking into whether or not you can just swap the ECU and tuck away the unused plugs (but you'd have to ask redline or imthedevil. They know more than I do).

G/L

 

So I was incorrect about the ecu, its code is 4B0 906 018 P.


The engine throttle is run by wire, not by cable.

And I did a cheap vacuum test and sprayed throttle body cleaner on the vacuum lines, and it didn't seem to affect the engine at all. Are there any better ways to check for vacuum leaks?

 

Figured out the p1287. There should be two solenoids under the intake manifold. one controls the SAI the other controls the diverter valve. Obviously the SAI one doesn't matter. However, it looks like your diverter valves line is ran right to the DV. This is okay on AEB, but not the way the ATW works. It isn't a huge a deal not to have the solenoid there, but it explains your code for that.

However, that will not explain your low vacuum. I am willing to bet there is an open nipple on the intake manifold or you have a large boost/vacuum leak elsewhere

 

Agreed with redline on the vacuum reading. Keep in mind guys, at idle you're looking at negative numbers, not positive. Your idle vacuum when the car is warmed up and running should be in the -18 to -22 range. A higher reading in the -15 to -10 range means you have a vacuum leak. Take that to the bank. Track down your leak (a shop can do a smoke test for you for probably an hour's labor or so) and that'll show you where your leak is.