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Title: N75 won't open so, no Boost :( Post by: Cooltim on February 02, 2019, 01:29:54 AM Hi Guys. I've been a member for over a year now and using these resources I learnt to remap my track car and my daily. It's an amazing wealth of information! Thanks to everyone involved. I have recently bought a B6 A4 1.8t. I've been fixing a few issues before I remap the ECU but I am stuck on a boost issue. The ECU won't close the N75 valve. The Wastegate duty (LDTVM) is almost always 0. Requested boost is fine but the car is stuck at wastegate pressure. The car had a few sensor issues, a bad O2 sensor which I've replaced and what looks like bad wiring to the G83 (radiator outlet) temperature sensor. It throws P1291 "upper level exceeded". I haven't fixed this yet but I don't think it should be causing the boost problem... One time, when I was logging to test the O2 sensor, the wastegate seemed to work fine. It still had the p1291 and the O2 sensor wasn't connected. I've included that log below. This is the only time it's closed in about 20 logged runs. Car is stock, stock map and the ltft was 0.8 I bought the car with a head full of bent valves and swapped the head, and the oil pickup was full of crap and the car had no oil pressure (I didn't see any evidence of damage in the cam bearings on the old head though.) Pressure is fine now the pickup is clean. Thanks to anyone who can have a look and offer advice! Tim. Latest log 2nd gear pull: https://1drv.ms/u/s!Aj6F6FcfWc2jgbptjasJ-LXw5TV0oA This one time that the N75 worked: https://1drv.ms/u/s!Aj6F6FcfWc2jgbpubJ8IDZAvdoy4Iw Title: Re: N75 won't open so, no Boost :( Post by: nyet on February 02, 2019, 11:23:09 AM Start with getting your coolant temps under control (sensor or actual cooling system problem)
Looks like the only time you saw wg activity was when it was <96C or so I'm seeing 100C in a lot of those logs which is very very not good. Title: Re: N75 won't open so, no Boost :( Post by: Cooltim on February 02, 2019, 01:43:33 PM Thanks Nyet.
That was the 3rd consecutive pull so that may explain the temps. Looking at logs where I wasn't just driving around town with my foot on the floor in second gear the temps stay below 97. Here is the first run that day with lower temps. Still no joy :( https://1drv.ms/u/s!Aj6F6FcfWc2jgbpqt6OEirg7APXt1w Title: Re: N75 won't open so, no Boost :( Post by: nyet on February 02, 2019, 05:54:04 PM Reset codes before EVERY run.. it looks like your ECU is in limp from something that happened previously.
Title: Re: N75 won't open so, no Boost :( Post by: Cooltim on February 02, 2019, 09:12:35 PM Is it just the Wastegate duty that makes you think that or something else in the data?
I still have the radiator coolant sensor error, maybe that's more important than I assumed. If it looks like limp mode I'll chase that down and see if it unleashes my boost... Tim. Title: Re: N75 won't open so, no Boost :( Post by: nyet on February 03, 2019, 12:28:43 AM Yes. WGDC of 0 or 10 means limp mode, period.
The entire purpose of limp mode is so you don't blow up your fucking car because you were too lazy to fix the coolant temp sensor, dude :P Title: Re: N75 won't open so, no Boost :( Post by: Cooltim on February 03, 2019, 01:04:05 AM It's not entirely that I'm lazy, it's just that the car is shit, and whenever I see wire there's a terrible spade connector terribly crimped to it courtesy of the previous owner and I just sit there shaking my head and sighing until the accumulated disappointment forces me to go inside and sit down. Thanks for the help though, I'll report back when I have it fixed. |