The Project Pad

One of the remaining items keeping me from a test drive is the brake master cylinder. It’s been on the car with the lines bled for a while, but it had a slow leak. I feared it was on the piston on this brand new MC, because I paid about $90 for it a couple years ago, but the only one’s available now are over $300 now. After bench bleeding it and letting it sit in my vice for a few days, I was able to confirm the source of a leak was at the rubber seals for the reservoir. So, I swapped the old ones on and it's been dry ever since. Let's hope it stays that way.





Was able to get some of the dash back together last weekend too.




And received this in the mail from Issam. I’m fearful my DIY drill/tap job on the stock extension is going to leak since there is very little sealing area on one side of the gasket.




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Happy to report the coupe appears to have working brakes and clutch. Got the master cylinder back on and it appears to be leak free. Also bled the system and was able to move the car at least a couple inches in the lift, to check for clutch engagement.

Put some Audi content on the shop wall too.





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Weekend recap…

Saturday was a big upgrade day for the coupe…installed a keyless entry with a switchblade key. lol

https://youtube.com/shorts/NGOkOJdJzYE

Also pulled it out of the shop for a little vitamin D and quickly realized the alignment was really bad. It looks like I turned the wheel to pose for a picture, but the driver’s side wheel was perfectly straight.






Using crude front and rear measurements on the front tires told me there was a 3-3/16” difference. Adjusted the the tie rods and ended up within 1/16”. Should be good enough until I can get it to an alignment shop.

Since getting it back in the shop, it’s struggling to stay running. Pulled these with my VCDS.

00523 - Intake Air Sensor G42 - Open or Short to Positive
00513 - Engine Speed Sensor G28 - No Signal

I thought I recall that the 00513 code is one of that will pop up when the engine dies, but could be wrong. Any ideas on the 00523? Are there tests for the G42?


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jbrentd wrote:
I thought I recall that the 00513 code is one of that will pop up when the engine dies, but could be wrong. Any ideas on the 00523? Are there tests for the G42?

From searching "G42" in the quattroworld UrS FAQ, located here:

https://forums.quattroworld.com/s4s6/msgs/15184.phtml

I found:

https://forums.quattroworld.com/s4s6/msgs/20996.phtml

Hope this helps. Lots of info there.

Berserker wrote:

jbrentd wrote:
I thought I recall that the 00513 code is one of that will pop up when the engine dies, but could be wrong. Any ideas on the 00523? Are there tests for the G42?

From searching "G42" in the quattroworld UrS FAQ, located here:

https://forums.quattroworld.com/s4s6/msgs/15184.phtml

I found:

https://forums.quattroworld.com/s4s6/msgs/20996.phtml

Hope this helps. Lots of info there.

Thanks for the reply! I was able to find the PIN numbers for the IAT sensor on the ECU plug. Didn’t see any continuity. So, inspected the connection and found this. I think I have it soldered back. The code went away, but car is still struggling to run/idle.




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Sounds like you fixed the idle sensor issue

I had a similar issue with the g28 that cause a horrible idle and affect on driving - a few things

1. If you’re careful you can remove it off the flywheel housing - it may just have metal attached to the magnetic end - clean it and check it out. You know this but remember It’s really easy to strip those Allen bolts or break that bracket.
2. You can test it without removing - check continuity of pin 1+2 to ~1000 ohm and 1+3 Infinite (open)
https://www.audiworld.com/forums/audi-o ... o-2802889/
3. In my case it wasn’t any of those but rather the g28 sensor resting directly on ignition wires and worn out insulation on the wire - definitely worth checking IMO

It is tough to find an OEM replacement and when you do it is either in the same condition or worse in my experience - I ended up finding an aftermarket replacement with a ‘g4’ part number as they are interchangeable. I ended up buying something just like this to troubleshoot which is how I found the issue - heck for 16$ it is good to have a spare especially if it is the G4 in the future. (Tip) if the car ever doesn’t start from a g4 no crank you could technically swap the g28 and drive the car home (albeit poorly)

https://www.ebay.com/itm/254483604240

Congrats on the moving and driving way to go car looks awesome

themagellan wrote:Sounds like you fixed the idle sensor issue

I had a similar issue with the g28 that cause a horrible idle and affect on driving - a few things

1. If you’re careful you can remove it off the flywheel housing - it may just have metal attached to the magnetic end - clean it and check it out. You know this but remember It’s really easy to strip those Allen bolts or break that bracket.
2. You can test it without removing - check continuity of pin 1+2 to ~1000 ohm and 1+3 Infinite (open)
https://www.audiworld.com/forums/audi-o ... o-2802889/
3. In my case it wasn’t any of those but rather the g28 sensor resting directly on ignition wires and worn out insulation on the wire - definitely worth checking IMO

It is tough to find an OEM replacement and when you do it is either in the same condition or worse in my experience - I ended up finding an aftermarket replacement with a ‘g4’ part number as they are interchangeable. I ended up buying something just like this to troubleshoot which is how I found the issue - heck for 16$ it is good to have a spare especially if it is the G4 in the future. (Tip) if the car ever doesn’t start from a g4 no crank you could technically swap the g28 and drive the car home (albeit poorly)

https://www.ebay.com/itm/254483604240

Congrats on the moving and driving way to go car looks awesome

Thank you! It feels good to have it running, albeit badly at the moment. And thanks for the info! I'll check to see if I have any issues like that with my G28. And a few other things to check, like the ISV, fuel filter, and fuel pump.

Cool, that G28 code should go away if the engine is running. For what it’s worth only once I replaced my actual ISV did the car ever idle correctly never threw a code would just chug around 800 rpm - well worth a new Bosch unit

It's been a while since I posted any progress on the CQ...

Since the last update, I did a bunch of troubleshooting and found some issues, but things got busy around the house when Spring hit and I kind of walked away for a bit. Here's a high level list of what I did/checked:

• Fuel - tested FPR, tested fuel rate, had injectors serviced, replaced fuel filter
• Spark - new plugs (some were soaked in fuel), found the old wires were bad, replaced wires
• Vacuum/Boost - found lots of boost leaks - replaced BPV (wasn't holding more than 2 psi), replace breather pipes and check valve with 034, found/fixed leaks at the injector cups. Would still like to do more testing with a smoke tester I bought on Amazon.
• Other - found/fixed a bad connection on the coolant temp sensor, knock sensor connectors were switched, idle switch wasn't making contact

I suspect the main culprits were the plug wires and the fuel filter. After replacing the fuel filter last weekend (something that should have been at the top of the to-do list), I was able to give it some throttle without bogging down. Brought her out of the shop for some time in the sun!



Still lots to do, but if she'll stay running well, I think it'll be downhill from here.

​Still plugging away at the CQ...

Had to get her off the ground for new front springs, so I thought I'd give these wheels a go.





Interior is shaping up.





I added an OEM cabin filter. Since these didn't come with a lid and the correct filters don't seem to be available, I might try to make some sort frame that will secure the filter a little better.



I am still fighting some issues with how she's running though. I've heat cycled it quite a few times, as I am flushing out the coolant system. When I start the car, it idles good at about 1,000 RPMs. After a few minutes, it starts to hunt between 1000 and 600. I've spent a lot of time looking for boost leaks and have found and fixed quite a few. I'm down to a couple small leaks...one around the throttle body boot and one on the ISV, but I do not think they would cause the issues I am experiencing.





I took it for a drive and it was bucking quite a bit under light throttle, not even into the boost yet. It feels like a loss of fuel to me.

I'm pretty sure I have some wiring gremlins in the harness that runs along the driver side (left) of the car. I suspect this is all some carryover from this mess I found a while back.

• When cranking or with the car running, my turn signal lights come on.
• With the car running, if I flip on the headlights, the car will die.
• The fuel sender signal to the instrument cluster gets lost when I turn on the headlights or step on the brakes.

As I was digging through the wiring diagrams, I noticed several of the circuits that are are having issues are on the H plug on the bottom of the relay panel. The H plug runs to the rear of the car.

• H87F G/Y - from fuse S13 to fuel pump
• H50w BK/BL - from relay 8 #39 to alarm control unit
• H30B R/BL - from fuse S4 to hatch light
• HT V/BK - fuel sending unit
• H58L GY/BK - from fuse S7 to rear lamp control unit 8b/5 (left side)
• H58R GY/R - from fuse S6 to rear lamp control unit 8b/6 (right side)

I need to get some time in the shop to check the voltage at the fuel pump to see if it's low on power or loosing power when I turn on the headlights. In the end, I might need to cut out a section of this wiring harness and solder in new wires.​

I originally had similar gremlins with my electrical on my previous 90Q. I ended up installing a stand alone fuel pump relay, used the trigger wire from the engine control harness over to the switch on the relay. This also allowed me to use larger diameter wiring to the pump.


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JH87 wrote:I originally had similar gremlins with my electrical on my previous 90Q. I ended up installing a stand alone fuel pump relay, used the trigger wire from the engine control harness over to the switch on the relay. This also allowed me to use larger diameter wiring to the pump.


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Thanks for the reply. I was thinking the same thing. Except triggering a 30A relay off the stock fuel pump relay. If what I think is happening is really happening, that should solve the fuel pump issue, but I may still have wires shorted to each other in that loom. But at least it would keep the car from dying.

Is the wire loom in decent shape? It would be annoying to undo all the fabric wrap and have it end up being corrosion or a loose termination on a common ground.


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JH87 wrote:Is the wire loom in decent shape? It would be annoying to undo all the fabric wrap and have it end up being corrosion or a loose termination on a common ground.


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You can see the 4 looms in that picture above. One of them was worse than the others. When I had the carpet out, I had to move things around quite a bit to repair the floorpan. I looked as best I could and couldn't see any breaks in the insulation. But I bet there are some. I kind of stuck my head in the sand and re-wrapped them in cloth tape.

After my work on the floorpan, here's what they looked like. You can see them at the top.

That all looks good, aesthetically and functionally. If you can get your hands on an insulation resistant meter, you can test pin pairs through the wires in each loom. This would at least rule out shorted wires. You can also try using a bonding meter at wherever the grounds in those looms terminate.


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JH87 wrote:That all looks good, aesthetically and functionally. If you can get your hands on an insulation resistant meter, you can test pin pairs through the wires in each loom. This would at least rule out shorted wires. You can also try using a bonding meter at wherever the grounds in those looms terminate.


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Any meter that can read to the milliohm range would work for bonding checks.

This would be the meter I’d recommend for insulation resistance testing:

https://www.amazon.com/Klein-Tools-ET60 ... 249&sr=8-3


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So, I hooked up my multimeter to the fuel pump leads to check the voltage and it is severely low. It is a wonder it even runs at all. Linked below is a short video I made with some annotations for when I toggle on the parking lights, headlights and just the brights. As you can see, I am getting less than 4 vdc.

I am fairly certain I have some wires touching to one another in the rear wire loom (contains power to FP, fuel sender, rear lamp control units, and a couple others. My plan is to relay the fuel pump. Triggered from the stock fuel pump power wire coming off the relay panel and powered from the battery with an inline fuse. My hope is that will fix the issue with it staling, but I still plan to come back and repair the shorted wires in that loom.

https://youtube.com/shorts/8HhgO5A6mA0? ... 514zfz_03H

I also managed to get a fuel pressure gauge installed and got some confirmation of the issues caused by the low voltage. Was only seeing fluctuation pressures between 15 and 25 psi. 3B uses a 3 bar regulator.

Then I was able to test the fuel pump by hot wiring it. With it running at battery voltage, I was getting 45 psi, which makes sense for the 3B 3 bar FPR. It was quite noisy, though. Always has been…which should have been my first clue all along. I was just hopeful it magically got quiet on me. lol. I should probably replace it with a new Bosch pump that I have on the shelf, while I’m in there.



 


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Certainly, as you plan, best solution is to isolate that circuit. Especially since you have everything out of the car right now. I have the Bosch 044 and I ran 6 gauge to it doing the same thing you’re planning… and voltage holds stable/no issues whatsoever. I also pulled the 120A alternator off of the V6 that I pulled from my car then changed the pulley to v-belt and installed it on the 3B. Hopefully that helps with the electrical woes I would have when my e fan would kick on since the alternator I had was only 90A.


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I am very happy to report that the fuel pump issues have been resolved, but the problem turned out to be a bad ground. After I got the relay in for the FP, there was no difference…pretty frustrating. Better up front diagnostics would have told me it was a bad ground. I was getting full battery power to the FP, when using the neg battery post to check. Versus the low voltage when checking voltage across the +/- wires at the FP.

After not being able to find the #50 ground post (supposed to be in the hatch somewhere on the driver side), I just tied in a new ground right in the loom going to the FP. Doing this fixed the FP and issues I was having with the fuel sender, turn signals and the car stalling when turning on the headlights. That #50 ground post is shared on quite a few circuits. The green wire is the new ground I added.






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Glad you got it fixed. Sometimes it’s more fun taking the long way home.


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Definitely the long way. I looked back at a video I took when I first started it up about a year ago and this fuel pump problem has been an issue since then. I could tell by seeing the turn signals getting power when starting the car. But it did force me to go through almost everything and verify things were working and I did fix quite a few things along the way. Hopefully, that pays off in the long run.

The one thing I am unsure of is why it became an issue in the first place. Water under the bridge...hopefully.

jbrentd wrote:Definitely the long way. I looked back at a video I took when I first started it up about a year ago and this fuel pump problem has been an issue since then. I could tell by seeing the turn signals getting power when starting the car. But it did force me to go through almost everything and verify things were working and I did fix quite a few things along the way. Hopefully, that pays off in the long run.

The one thing I am unsure of is why it became an issue in the first place. Water under the bridge...hopefully.

Probably water under the bridge and a one off issue. Root cause analysis on a 90s era German car’s electrical system would almost be done in vein.


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As if this project hasn't had enough scope creep, I received a package from UPS the other day that I am excited about.

My DIY coilovers are a little tired and I have tried several combinations of springs, both with and without helper springs. I just can't seem to get a decent ride out of them. I am sure most of the problem lies with me, but I am tired of throwing money at them. So, I am going to give these BC coilovers a try. I like that they have fully threaded bodies that allow height adjustment that is independent of adjusting the lower spring perches that are supposed to be for setting spring preload. And the struts have C/R adjustment knobs as well (something the Bilstein struts on my DIY set don't have).

Nice to see someone took the plunge and ordered a set. I look forward to hearing what you think of them.