I did a 1.8t conversion on an mk4 bora (originally 1.6 simos) using a BBU engine from an ibiza 2005. The car runs and drives but ecu seems to close the throttle at 4000rpm Rpm holds 4000 at wot boost dies off. It's a 5 speed manual. does the same in neutral and sounds like a rev limit. MAF unplugged makes no difference. Fueling seems ok. Don't yet have a vss signal for the ecu or cluster. Not sure if this is a problem. TBA gives me a error. The codes present are about can-bus missing message from ABS controller and instruments cluster. Does anybody know if this is a limp mode or if something else is happening. I'd appreciate any help with this. Thank you
does sound like limp mode from missing VSS, on the ibiza loom looks to be purple/white wire. its from ecu pin 54 regardless and wand wiring up to the blue/white wire on the MK4 orange plug
Thank you very much sir. I greatly appreciate your knowledge. Your posts on this forum have helped me throughout this project and others. As soon as I get the vss I will update. Some more info on the car - I am using the ibiza engine loom (small plug on ecu) But I am using an automatic AUM loom (a3) for the maf/o2 harness (big plug on ecu) and colorful plugs The ibiza cluster is quite different from the mk4 and won't plug in with the blue/green plugs so I'm using the original mk4 cluster (1.6 automatic) with the immo removed. I believe the BBU ecu is stage 1 or 2. Forge DV Thank you again.
I managed to get a pit of the cluster working today. Have not yet got a correct diagram for the g22 sensor to the cluster. I understand how to get it from the cluster to pin 54, it's the input to the cluster I'm looking for. I think it's pin 28 on the t32b to pin 2 on the sensor. Where is it powered from? A fuse? 5v? All I have is the sensor no where to plug it in. I got to wire up a small loom with a 3 pin connector I have. The automatic loom is run different and I think it goes to the TCM plug.
Ok I got the signal working on the dash. Pin 2 and 3 on the t14 by the battery. Now I'm looking to confirm which pin the blue/white in the orange plug should be coming from at the cluster before I put the wrong thing in the ecu.
Vss is all working now but the problem still persists. Limiter at 4500 or so. All wires connected. Only cell comes from o2 sensor bank 2. Post cat isn't plugged in. Don't think that's causing it tho. Any ideas?
Ah sorry I thought you just meant the ecu VSS signal. For the cluster speedometer its the white/blue for signal and black/white for power in the t10a or t14a plug on the MK4, then you tap the earth to wherever handy, though you've already fixed it: https://clubgti.com/forums/index.ph...install-faq-now-with-added-dieselness.267196/ ECU pin 54 is the speed output from the cluster which is the blue/white wire on the orange plug, but that is already taken care of by the big plug ecu loom you used from the A3 as it makes no difference to running with maf unplugged, thats where I would start I recon
Thanks again. You right the pin 54 was already sorted. Just needed to get it to the clock. I'll check over the maf and the rear o2 today. Great thread btw. I think was using an older version of it. I probably would have never found this one with a title like that. Gona keep it close
The maf looks like it's doing the correct thing. I got the rear o2 sorted and the CEL came off. Can I rule out limp mode? I tried putting 12v at the clutch switch incase maybe it's causing a rev limit. Still 4500rpm and around 3lbs boost
ok now you have the post cat code cleared can you try the TBA again? though I guess it wont be needed if the ecu hasnt thrown a code for it. Have all the parts come from the same car and was it all running perfectly? As if you have a missmatch of ecu which has been mapped for a specific size maf and set of injectors and you then change those things then it can and usually will mess things up. the canbus comms errors you mention shouldnt cause any kind of limp mode as far as I know, but they can be switched off by a competent ecu coder if you feel the need.
Yes I forgot to mention that I was able to successfully do the TBA right after the light came off. The engine and ecu come from the same car. Maf is from AWP. Ac compressor and accessories + bracket are from bora (BBU has a different set up with electric powersteering so I added power steering pump and clutch style compressor. Removed SAI and a mk5 style secondary coolant pump. (BBU is a very strange 1.8t) Came with vacuum reservoir and n249 etc deleted Changed the gearbox to o2j from the original o2r O2 sensor is from bora 1.6 bfq for the front. Fuel pump is from the ibiza Aside from all that. I am noticing that my fuel trims are not adjusting at all. 0% in all fields long and short. I stupidly thought they were ok. Also coolant temp is reaching the ecu but not the cluster, and the reading seems to be off. Iv used a resistor to try get it where it should be but I want to properly sort it out today. I dont actually know how well the donor car was running. I bought the engine from the UK and shipped it to trinidad here. I physically looked to be in good condition. Turbo is good.
ok, if the coolant sensor is reading wrong get that swapped, use a mk4 golf 4 pin one and wire it up the same as it is on a mk4 20v job done (the old 1.6 one will work fine) just make sure you get the pins wired right as the ecu and dash sensors have different resistance curves
I'm using the 1.6 sensor with 4 pin. Seat only had 2 pins feeding the ecu. The wire for the guage seems to be mixed up with the SAI valve. I noticed that SAI valve n75, n249 and vvt wasn't getting an ignition feed from the t14a. SAI also is the only one going through t14a. I think I have work to do on that connector. I have no sai relay. Do I need one? It's giving me a code every now and then.
you can have the SAI coded out fully if you like, if you dont you'll get codes for it though it wont affect running afaik. yeah i think you'll want to go back over your harness, I have the diagram for MK4 AUM/AUQ plus the BBU in my signature you'll be able to figure it out from that
Finally got the chance to try the BBU ecu in another car. In my AUM golf. It's doing the same exact thing more or less. Limited rpm at 4.5k and just about no boost.
I didn't want to interfere with ECU from the aum. I have a spare ecu from an c5 a6 that I had unlocked and put in the bora now the car is boosting correctly and reving all the way to redline. The problem is finally solved. Thank you so much for your help. Greatly appreciated. I sent the BBU ecu to be repaired or reflashed with original software and eventually I'll put back a tune with that ecu if it isn't toast.
the sad part is that i repinned the entire 1.6 harness and it was working before I got the aum one thinking I did something wrong but it was the ECU.
