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.

Hendie

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.

nallegam

Cool to see another enthusiast owned 200 20v

The only time I encountered a situation similar to yours was when:

1. The boost line to the ecu was leaking - Make sure the vacuum lines are routed to the back of the manifold correctly and there are no cracks anywhere, even if you have already checked once. Check the manual for the correct outlets to use. This would also be why you are seeing an over boost condition - the ecu continues to not see boost and requests it. This could also be the sensor measuring the pressure in the ecu.
2. I have also found that any crank/rpm sensors crossed on top of knock sensors or spark plug wires create some situations that feel like 'boost cut' and can create some really bad misfires, but doesn't sound like the case. Proper routing and new wires help a lot.

I saw a few other posts and here are a few suggestions as well:

- Check all your grounds/power - Engine Bay, Alternator, Battery, it is mind blowing how much these can solve.
- Check your plugs and gap them correctly - I used to be obsessed with getting the OEM plugs, but I have actually had the most luck lately with the bkr7e - they are very cheap and readily available.
- Avoid hitting overboost! As much as you may find it annoying, the car is actually saving itself. These motors are getting pretty rare.
- The knock sensors will help, definitely worth replacing. There are a few interchangeable versions, but the lengths aren't perfect.
- Safety - Check the hydraulics/Braking system - Boxster upgrade is nice and cheap there are also a lot of good options for brackets, lines, and part replacements if you know where to look.
- Change your fuel filter - My tank has got a bit rusty and it's good piece of mind.
- I think the stock airbox is nice to keep on, though I do often dream of more turbo noise
- If you don't know what chips are in your ecu I wouldn't drive it in boost to be perfectly honest - contact efiexpress or find some stock chips to put in. You'll be chasing strange problems endlessly for no good reason.

Also check out - theprojectpad.com, motorgeek.com, s2forum.com, forums.quattroworld.com

If you also find an old broken link or picture or thread - try to use the wayback machine https://archive.org/web/ to warp back in time to see it (ymmv)

Hope it treats you well and good luck!

Hendie

It was the wrong n75 and it was installed backwards!