Can I put an AHU ECU in a MK4 ALH car?

[PB_NB]

I recently had a Stage 4 tune installed in my car. 1999 ALH New Beetle.
The car has tons of power but isn't the smoothest with a low speed miss and high rpm stumble. I have a CEL for my EGR system, but my original ECU had EGR delete programmed into it.

So since my upgrades I have been working on tweaking the ECU by setting timing, IQ, GP delay etc...

The car still doesn't feel right so am I to think that the MK3 AHU ECU, part number 028 906 012 FA wont work with my ALH? My original ECU part number was 038 906 018 BK. I discovered the part number difference when looking at my old log files and comparing them to my new ones.

I think I may need to get my old ECU back as I may not be able to make this MK3 unit work with good results. Any feedback will be appreciated.

 

[JETaah]

Turbo control is different on the MK3 at the very least...waste gate vs VNT on the Beetle.
There are many physical differences. MAP sensor is inside the ECU, harness connector is different.

You'd be better off buying a salvage early Beetle ECU and starting over if you want both stock and stage 4 scenarios available.
Make sure it gets the hot start fix modification if it is the early type. Talking to a tuner would be best.

 

[PB_NB]

Thanks for the reply. The ECU fits in the car and is plugged in. The problem I have is after I got it back from getting a bunch of upgrades (done at a shop) which included the stage 4 tune, I have some drivability issues. It took me a bit to get my VCDS cable and now when I scanned the ECU I get the AHU part number, It used to be my proper part number as shown on an earlier scan.

My thought was that the original ECU was swapped with the AHU version but if they don't actually fit, I cant see that. I just don't understand why the scan is reading it as an AHU ECU.

The issues I have are stumbling at wide open throttle. Poor running at just above idle sounds like a miss.

I had a really hard time adjusting my IQ to 4.0. I had to hammer mod it many times to get it down to 4.0. Had no trouble before.

The car is very smokey at startup and wasn't before. Timing is set according to VCDS on the advanced side but within the lines.

EGR system is throwing a CEL (had EGR delete in the tune before)

Had Hot start issue in the tune but don't really know if it is back yet.

I am getting a flashing glow plug light and the strange part is that the sequence of bits ie: (0,1,0) are both reading with "1" in the first position. I am not too sure if this has anything to do with the brake controller installed at the same time but both switches are off now.

Car was trouble free before the updates. ????

 

[BobnOH]

As far as I know only an ECU with the same part no. can be used.
There may be things a chip programmer can do to make one ECU work in a different car, don't know.

 

[compu_85]

You could likely use the ECU from a 99.5 Golf or Jetta, which may be easier to find.

A Mk3 ECU won't work in a Mk4 due to the differences JETaah noted. Plus, on your 99, there's CAN between the ABS and ECU (and automatic if equipped). The Mk3 / B4 never got CAN.

-J

 

[BobnOH]

If you get one get the same part no. car-part should have them, between $150-$600.
So the ECU you're using has a stage IV tune plus some mods you've made. If you undo all your mods, does it run good?
I'm wondering what your IQ was with just the tune. The spec on that is like 2.0 to 9.0, there is no single perfect number for all cars after we replace injectors, turbos, pumps, etc.

 

[PB_NB]

At is point I really don't know what I have for tuning mods or even the tune??

The car goes but it is not well behaved. It is like driving a Molotov cocktail. 160hp/313tq in the little car is quite a bit of power. I am a bit worried about the turbo now hearing about the Mk3 ECU and how it doesn't work with the N75 valve.

I am trying to get my original ECU back from the shop if a swap actually happened and then I can start there.

I haven't tried undoing any tuning as I just discovered this part number last night when I was looking at a recent log I pulled after the swap.

i just cleared the Faults so the EGR had not come back yet. See below:

+++++++++++++++++++++++++++++++++

Address 01: Engine Labels: 028-906-021-AHU.lbl
Control Module Part Number: 028 906 021 FA
Component and/or Version: 1,9l R4 EDC G50SG 1405
Software Coding: 00002
Work Shop Code: WSC 92619
VCID: 53AB73C6A1D0C0DA24-4B18
Fault Codes have been Erased

3 Faults Found:
01266 - Glow Plug Relay (J52)
31-00 - Open or Short to Ground
00750 - Warning Lamp
31-00 - Open or Short to Ground
00741 - Brake Pedal Monitoring
27-00 - Implausible Signal

Readiness: N/A
+++++++++++++++++++++++++++

I think i am reading this correctly when it refers to AHU and if I google the part number it comes up with Mk3 or B4 cars.

 

[BobnOH]

That one fits a '97 Passat, I'd try contacting the person that did the ECU work.

 

[PB_NB]

I had a chance to drop in to Malone's to see if we could figure this out. It looks like I now have the proper tune in the car with the proper physical ECU and everything that was ailing the car went away. The stumble when I pushed it is gone. The miss just above idle is gone. The CEL is gone and so is the flashing glow plug light.

I can feel a difference with the go pedal as it is now very predictable and power is there based on the pedal input.

The smoke is down a bit at WOT and the car is not stinky at idle.

Looks like all my problems were related to this tune.

The only difference is that now the car doesn't have as much power as before. It feels like I lost my NOS button.

My hope is to get the car back on the dyno soon and see where the power numbers are now.

I also have to hook up the trailer and see how the engine pulls it around.

 

[turbovan+tdi]

I was going to suggest popping in to see Malone, I was there Yesterday, stage 2+ on my wagon and damn, she's fun to drive now,

 

[PB_NB]

I have to say that the experience at Malone's today was pretty good. The guys were extremely helpful and really wanted to make this work.

Thumbs up for Mark, Keir and Owain.

Time to get the Cooper in to see what they can do with it