Hendie

Thought I'd introduce my self. I'm Nicholas I've got 2 Audi 200q 5cyl. And a 200q parts car. Currently getting an overboost fuel shut off at about 10psi. It's a 1991 Avant 20v 3b. I'm running down SJM's overboost check list. The most my Chinese can/bus scanner will tell me is 0544 over boost(It's still handy in a pinch). So far I've
Correctly routed the vac lines
All new vac line to ecu
Vac tested the ecu to 15 hg no leak
Diverter valve vac tested no leak
Wastegate Vac tested no leak
MFTS plug repaired
MAF and connector cleaned
Air filter cleaned- thinking about putting the stock air box back in. One of the POs removed
New 87c thermostat
New knock off rad fan(need time to rebuild the Bosch ones I have laying around)
New rear blue Bosch knock senor( waiting on front brown from UK)
034 turbo hoses installed (almost still need to do the T.B. hose)
A spare inst cluster out getting repaired by a relative.

Going to order new Nologys found some chaffing
I'll gets some Bosch F5DPORs while I'm at it.
Also debating on opening the ecu to locate any supposed mods. ( The car may have had a 2bennett chip at one time how ever I know PO used ecu to test his dad's car, may have stayed there or mixed with another ecu he had lying around plus I got the info about ecu from the Avant registry who know between then and now?) Root Beer Brown Avant any info on it would be awesome. Would be nice to know how much boost my ecu is expecting.


Hope I fix it before SJMs check list ends. I'd like to paint her soon.
Quote Multi
#2

Hendie , 01-08-2019 08:24 PM
Ecu / overboost
So I pulled the ecu and it appears to be stock according to ( http://www.quattro123.com/MPTSAudiECUupgrade2.htm ). Same blue slash mark and numbers on the chips. So it seem I do have some actual overboost after all. Not just the code. Never trust always check. Still doesn't explain the overboost fuel cut at 10psi on aftermarket boostgage independently plumbed. Or the intermittent fuel cut above 1.2 bar via inst cluster. The cluster has gone as high as 1.8 bar. Boost Gage I've seen spike to 20 psi. Scarry for stock. The inst cluster reads .3 bar when the boostgage reads 20 hg. I will continue with SJMs check list starting at the bottom. All suggestions welcome.

Now I disconnected the wastegate frequency valve(n75). No overboost code with it disconnected. But I'm now boosting up to 20psi on a stock set up. This is sceaming waste gate issues to me.
The n75 clicked when I put 12v to it. Also tested to 28 ohms.
Someone please help me put all of this together.

Hendie

So I pulled apart my wastegate the diaphragm is holding vac and the valve moves freely. Why am I getting 20psi??? (Even with the n75 disconnected) I adjusted the spring tension to allow the wastegate to open sooner. Previous owner never had these issues. Someone please help.

Hendie

Now I am getting codes 01262 and 0544. Wastegate frequency valve(n75) and overboost cut out. I ordered a new n75 hope this fixes my overboost.

Hendie

So I feel like an idiot. I was getting code 01262 because I unplugged the n75. But I backed my waste gate spring off 5 full turns. It now comes close to holding 13 psi but will still go to 20 psi this is with the n75 still disconnected. I've looked at to many different potential issues my head hurts. I can't be the only one still working on a 20v. This is my second turbo car (first being my 90 10v) I'm still new to them.
maybe blocked cat?
Fuel problem?
Spark or ignition problems?
Still have a boost leak?
anyone????????????????
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Hendie

Installed. Working on making the pressure tester. Also got a new oem n75j I plan on installing tomorrow . Cleaned the contacts on my MAF again. Vacuum tested the FPR holds 20 in hg. Find out on my way to work if I'm still hitting the fuel cut.

Hendie

So I pressure tested my intake and my oil cap was leaking around 10 psi. Held it down and didn't hear any other leaks. I assume from my understanding this is considered a boost leak?

yodasfro

You want to remove the oil filler when doing a pressure test to prevent blowing out any seals in the crankcase along with blocking off the crackcase breather.. Sounds like you are on the right track just keep checking stuff. I suggest checking and adjusting the TPS and also check the BPV to see if it holds vacuum. The main places 3B leak boost is the o-ring seal on the intercooler pipe and the throttle body hose that's not to say other hoses aren't leaking. I'd try to see what chip and pressure transducer are in the ECU and if the WG spring is stiffer than stock. Plenty of info in the s-car faq on QW this place is pretty dead these days.

Hendie

Should I block the crank vent at the MAF to turbo? And on the driver's side of the block?
Diverter valve held vacuum. I opened the ecu and it appears to be stock(see next post). I'll test the TPS this week end.
Also could the wrong n75 cause over boost?
Thanks
Nick

Hendie

Appears to be stock?

Hendie

So I finally got time to pull my n75. It's the wrong one and I believe it was in backwards. From my understanding that could allow boost to build indefinitely preventing the ecu from properly regulating boost? Any way the correct n75 is now intalled the correct way! Also put on a new oil cap. And new line from n75 to waste gate. Crossing my fingers!