After some substantial troubleshooting of the starter I think I’ve finally resolved the intermittent start problem. My best guess as to the fault was that the grounding wire that runs from the engine block to the frame was not making a good connection. I say this because I hooked a jumper cable from the battery negative terminal to the lower bolt that holds the starter motor in place, and with that connection made the car starts fine. I did a bit more monkeying around with the various connection, including the one from the engine to frame, and since then it has started as expected.
Getting this abomination of an exhaust on the car continues to be an exercise in aggravation. The mega-can at the end of the exhaust is such a large diameter I had to rummage through some long bolts that I have to find one that reached from the exhaust hanger to the car. Then the midpipes are slightly off on the driver’s side, this doesn’t come as a surprise since I cut a section of the exhaust out, but I’ve now made it challenging to find a suitable piece of piping to join the two section together.
Upon initial startup I received a couple caution indications, the washer fluid low and the brake pad wear sensor. There’s no fluid in the washer reservoir so that was no surprise, and as for the pad wear sensor I’m pretty sure it’s a bad sensor as there’s a good amount of brake pad left. I was glad that the oil caution did not come on, amazing how that works when you attach a wire to the sensor.
The first start led to an open circuit fault on cylinders 4 and 6. I pulled off the injector adapters and reseated them which seemed to help since during the next run the faults did not return.
I logged the O2 sensors since I am suspicious of how well these generic sensors will work.
That’s not good. Looks like I’ll be yanking the passenger side and sticking in a replacement.
After yesterdays non-start event and my suspicion that the Starter motor might be faulty I decided to pull the starter out and do a ‘bench’ test on it.
I pulled together some suggested steps for the procedure and commenced removing the starter. After extracting it I conducted the bench test:
Starter Motor Bench Check
Looks good. So much for that hypothesis. I’m now wondering about the starter engagement with the engine, but I’ll do some more troubleshooting and see where that leads. For the time being I get to have fun putting the starter back in place.
What follows are the steps I took to remove the starter motor. These were provided by Audizine forum member DxC. The only deviation I performed was to do step 10, removing the IC hardpipe, after step 5. Getting the IC hardpipe out of the way earlier just made more room to get in where I needed.
Remove headlights and bumper,
Remove all rad support bolts and just slide it forward (don’t disconnect coolant)
17mm on tensioner to get the accessory belt off
8mm allen and 13mm bolts to get the alternator off …
Once its loose undo the plug and 13mm on the back of the alternator
Pry/tap the alternator out of the way and take it out …
Undo the connector and 13mm on the starter (use a deep socket 13mm)
Undo the AC line holder (13mm nut),
Intercooler hardpipe (2 – 5mm allen) and IC hose, and
Also the turbo outlet coupler (I take it off all as 1 big piece)
Now undo the 16mm bolts holding the starter in … u have to go in from the back of the subframe … the bottom bolt has a 16mm nut on the front side that you can hold with a long extension on a ratchet …
Once the bolts are off, you can just barely finagle the starter out …
Today was the day I was tentatively to have tried starting the Nogaro. I still haven’t put the exhaust together so it isn’t quite in running condition, but I had hoped to run it briefly to check on what Fault codes are still being thrown. I’m expecting the brake pad wear sensor, washer fluid level sensor, possibly O2 sensors, and probably some random misfiring or other poor running indicators resulting from the base tune not quite matching the hardware.
One of the issues the person I bought the car from was having was intermittent starting, which they believed may have been caused by the clutch safety switch starting to fail. They had bought a replacement switch that they gave to me, but when I got under the dash and investigated the switch I discovered that a prior owner had completely bypassed the switch, joining the two wires that normally would have attached to the switch.
I’m anticipating I’ll be spending a bit more time under here trying to understand what the previous owners were thinking when they started splicing into various wires.
One of my first efforts here will be to relocate the boost gauge to the Podi column mount – also supplied by the seller.
Unfortunately the intermittent start issue is persisting, though for the moment it’s not intermittent, it just isn’t starting. I tried by-passing everything and having the engine turn over by connecting the starter to the battery, but even that did not succeed in turning the engine over. I’m now suspecting the starter may be the culprit.
A discussion on water-methanol injection encompassed the subject of check-valves and their use with nozzles. This further expanded to ponder the question of how much, if any, vacuum was present in the bipipes where WMI nozzles are most commonly located.
My personal experience has been that the flow rate through the Flow Sensor is different when nozzles have check-valves or do not. What I have observed is a brief spike in the flow rate through the sensor upon system activation if the WMI system has not recently been operated. I’ve attributed the spike to the system pump filling the lines, which results in a higher flow rate than is sustained once adequate line pressure is achieved, followed immediately by the WMI spraying into the intake pipes.
My assumption has been that when the system is not active and the car is running there is vacuum in the bipipes that slowly draws out the water from the WMI lines. The discussion about check-valves raised this subject, and I decided to take a pressure reading of the bipipe with the car idling to find out if my assumption was correct.
I’ve got a Dwyer magnehelic differential pressure gage that is well suited to this experiment. Drawing slightly on the low pressure port by mouth causes sufficient vacuum to move the needle, thus if there is vacuum in the bipipes this gage should be able to register it.
I decided to attach the gage to the car at the WMI bung that is located on the top end tank of the intercooler. The position is near enough to that on the bipipes and would be easier to access since I did not already have a WMI line running to this location.
I used play-doh to seal the hose to the WMI bung.
Then I started the car and checked the pressure gage:
Nothing. No movement from the needle at all. I confirmed the hoses were sealed well and still no difference. Inside the car the boost gauge, that is fed from the intake manifold plenum, was reading:
So much for my theory that vacuum in the bipipes is what was causing the WMI flow spikes that I recorded without the check-valves.
My new theory is that airflow past the nozzle creates a venturi effect that draws the fluid out.
Today I continued the effort of putting things back together. As this is a repair and replace effort going on in conjunction with the buttoning up it’s taking a while longer than it normally would.
After the passenger side axle went in I also installed the new wheel well liner for that side. I was also cleaning oil and dirt residue off the intercooler pipes and hoses so something like re-installing the IC’s entailed more than simply re-install the part.
I was pleased to observe that the accessory belt contained an Audi logo, I was concerned I’d find a no-name brand. I had to hunt around for a little while in my spare nuts and bolts box to find a bolt to hold the AC compressor in place – a previous owner had chosen to install the part only using two of the three bolts. I could see skipping a fastener or to on the wheel well liner, but not on something like the AC compressor.
I’m doing away with the K&N cone filter and BMW MAF housing, in exchange for and EPL MAF housing, adorned with 034 Motorsport stickers of all things, that was in the Nogaro’s trunk. I’ll be reverting back to the stock airbox.
Another puzzling thing I found was that a prior owner had removed the bracket that the wiring harness attaches to beneath the coolant reservoir. Without the bracket the harness hangs down closer to the exhaust manifold, not something I’m fond of, so I wrapped the harness in aluminum foil and tied it up underneath the the brackets for the reservoir so it has some protection from the heat below.
I still need to make up some joiner pipes for the exhaust, but I’m getting close to starting this S4 back and, and begin troubleshooting any remaining issues.