jbrentd's 2nd Chance CQ

[Jaswan]

Hopefully that's an easy fix for the brake master cylinder!!

Jase.

[jbrentd]

Hopefully that's an easy fix for the brake master cylinder!!

Jase.

I hope so too. It's been good for a few days in the vice on my workbench.

[jbrentd]

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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[jbrentd]

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]

I was able to confirm no continuity for the IAT sensor on the ECU plug. 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.

[Tom_]

I found the old connectors very brittle. Not sure how old are yours, but some of mine cracked during the continuity test

[jbrentd]

I found the old connectors very brittle. Not sure how old are yours, but some of mine cracked during the continuity test

That is definitely true. Found a couple other of types issues.

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

After I got the swap running, it was idling great at first, but progressively got worse. It would fire up, but then struggle to stay running. 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, fuel filter and the boost/vacuum leaks. 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.

[jbrentd]

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.

[Tom_]

Nice progress Brent. Did you check those wires back then? Maybe I will look at what these wires look like...Remove that tape and see if there aren't any
short circuit or insulation failure

[jbrentd]

Nice progress Brent. Did you check those wires back then? Maybe I will look at what these wires look like...Remove that tape and see if there aren't any
short circuit or insulation failure

I looked at them briefly, but kind of stuck my head in the sand and just wrapped them with cloth tape and moved on. Probably not the best idea.

[jbrentd]

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/8HhgO5A6m...87pQNWuGYdEIpV

https://youtube.com/shorts/8HhgO5A6m...87pQNWuGYdEIpV


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[jbrentd]

I 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.

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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[newsh]

Mine actually melted the main fuel pump fuse in the fuse box, the contacts in the box were dirty or loose so got hot, I now just use that fuse to relay the pump direct from the battery.

I also had problems with the loom under the carpet on the drivers side, the loom makes a sharp bend into the plastic trunking and some of the wires had broken insulation which allowed the moisture to penetrate the conductors ( there’s always damp in a coupe somewhere isn’t there..) The copper strands then rotted away, the rot can travel up the wire even if it looks ok and it’s just a small crack in the insulation. I ended up cutting quite a lot of wires out, back to good copper and splicing new wire in, I worked one wire at a time and added a bit of slack then used self amalgamating tape over the joins, it’s been fine since. When I finally managed to fix the water leaks I stripped out the old fibre underlay and replaced it with Dyna Mat products which are modern closed cell deadening foams which don’t absorb moisture.

[jbrentd]

Mine actually melted the main fuel pump fuse in the fuse box, the contacts in the box were dirty or loose so got hot, I now just use that fuse to relay the pump direct from the battery.

I also had problems with the loom under the carpet on the drivers side, the loom makes a sharp bend into the plastic trunking and some of the wires had broken insulation which allowed the moisture to penetrate the conductors ( there's always damp in a coupe somewhere isn't there..) The copper strands then rotted away, the rot can travel up the wire even if it looks ok and it's just a small crack in the insulation. I ended up cutting quite a lot of wires out, back to good copper and splicing new wire in, I worked one wire at a time and added a bit of slack then used self amalgamating tape over the joins, it's been fine since. When I finally managed to fix the water leaks I stripped out the old fibre underlay and replaced it with Dyna Mat products which are modern closed cell deadening foams which don't absorb moisture.

Thank you for the info. Peter actually pointed me to your build on FB. I'll have to look at the fuse. I ran out of time yesterday as I was installing a fuel pump relay. My battery has been relocated to the trunk, so most of the wiring is pretty simple and short. The only wire I have left is the trigger.

And thanks for the tips from when you dealt with your wiring issues. I will give those wire looms a thorough inspection as I repair the known bad sections.


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[Tom_]

Glad you find the problem, Brent. How long is that fuel pump wiring section? It goes from the relay to the rear lid of the pump? I will make a new fuel pump harness directly from the battery, the old fuel pump relay will be triggering another relay for the pump itself.