Car Cranks But Doesn't Start. Also Hi, New Owner

4.2 V8 32v Naturally Aspirated - 414 bhp
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vr6geek
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Car Cranks But Doesn't Start. Also Hi, New Owner

Post by vr6geek » Sat Feb 04, 2023 11:36 pm

I wish this weren't my first post here, but here it is!

I recently picked up a 2007 RS4 with around 142,000 miles on it. I knew it'd need some TLC mechanically, but cosmetically it's in pretty good shape.

Less than a week after picking it up, I started to have intermittent starting issues. The first issue was the car not even turning over. After several tries, it'd eventually turn over and start right up. After starting, I'd have issues with lurching under hard throttle. I found one of the causes to be a bad clutch switch. I replaced both "in" and "out" switches while I was at it, just so I wouldn't have to deal with cruise control issues in the future. I also reset the throttle calibration, which seemed to fix my lurching issue.

I replaced the cabin filter, engine air filter, hood and trunk struts, and the car was running and operating great. However, every now and then the car would crank with no start when cold. If I let it sit for a minute or 2, it would usually start right up and be able to start again if I shut it off and didn't let it sit too long. After about a week of daily driving like this, I attempted to start the car in my garage, and could not for the life of me get it to start. I scoured the forums, and found that common issues are fuel filter, fuel pump, the relays under the ECU, and the crankshaft position sensor. I replaced all of these items, one by one, and tested for start-up as I went. After all of this, the car just cranks with no start. While cranking, the tachometer rises to maybe 200 RPM. I can hear the fuel pump prime when I turn the key in the ignition. The car cranks strong until it cuts the starter off automatically. At this point I'm stumped. Unfortunately I don't have access to a scan tool yet, but it's next on the list of tools to buy. Are there any other items I need to be checking? I did notice that the passenger side high pressure fuel pump is leaking a very small amount of fuel. I wouldn't think this or a faulty spark plug or coil would cause the car not to start at all though.

Any insight or suggestions would be appreciated. In the meantime, I'll get a scan tool ordered and continue to fiddle with relays and fuses to see if something electrical is the problem. I'm also going to inspect the throttle body to make sure nothing is blocking air from getting to the engine.

I'm hoping I can get this issue resolved and really start enjoying the car! A carbon clean is definitely on the schedule, the car is throwing a headlight code (probably the aftermarket LED parking lights), and I think the shifter could use an adjustment. Other than that, if I could get it to start it'd be ready to go!

vr6geek
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by vr6geek » Thu Feb 09, 2023 3:10 am

Update: I was able to get my hands on a basic OBD2 Scan Tool, and it pulled a single code: U0115 - No Communication with ECM B.

I looked into this online, and apparently a failing battery can sometimes cause problems like this. Grabbed a new Interstate AGM from Costco, no dice. Then I peeked underneath what I'm assuming is ECM B (the one in the middle of the engine bay where an A4's battery would go?). There is a brown ground wire coming off of that wiring loom. It looked rusted where it attached to the firewall. I sanded it down, re-attached it, and the car fired up. It ran rough for a little bit, then I decided to shut it off.

If the issue is this ground wire, I'm wondering if it was even attached in the correct location. It seemed like it was stretched to its limit, and the terminal connector was mounted to the firewall/brace running across the engine bay (under one of the 2 6mm hex bolts that sit about 2 inches apart). Is this the proper location for this ground?

Hopefully this is the root of my problems and I won't need to invest in new ECMs. Any pictures of RS4 engine bays around that middle ECM would be much appreciated so I can compare ground locations. Thanks in advance.

KNN
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by KNN » Thu Feb 09, 2023 7:25 pm

Hi VR6Geek, before proceeding to change battery or starter, worth trying these too:

1. Plug in scan tool, read all the errors and save the errors.

2. Check the voltages, if all are in good range.

3. These cars need good battery, Audi recommends VARTA. Battery size DIN110. The VARTA battery model which I got was VARTA 61038 (12V 110Ah 900A).

4. It will be a good idea to clean/wire brush/sand all the ground contact points.

5. Check starter ground wire, either add a new wire on top of the existing one or replace them with original part or even thicker/better ones. Why starter wires? Because if your car had the famous engine oil cooler leak, then the wires are constantly exposed to oil and heat which might deteriorate the wire condition or connection. Fix the leak if possible with Forge Oil Cooler and then take care of the wires. Replace starter ground wire if it is in a devastating state, with pure copper and probably thicker cable with proper insulation.

6. If scan tool shows starter relay faulty - change them. There are two relays for starter Relay 381(Purple in colour), located at the fuse box area below steering column. Make sure to mark the date of replacement for future reference.

7. Then, replace clutch pedal position switch. There are two pedal position switch, upper and lower, replace both position switches.

8. Also, update your fuel pump relays inside the fuse box located at the firewall area beside brake servo. There are two fuel pump relays, old fuel pump relay marked as "614" in light brown, new fuel pump relays marked as "644" in light green. Again, mark the date of replacement for future reference. You may ask why fuel pump relay? Because usually when you turn on the ignition, you should hear the fuel pump turning on/buzzing sound briefly for 1-2 seconds, if you don't hear that, then your relay is not working properly. Again, you can test this by pressing the gas pedal briefly for 1-2 seconds while key is at "ON" position, you will hear the fuel pump working/buzzing sound. If you only hear while pressing the pedal but not when you switch on the ignition, then change the fuel pump relay, you will hear them every time you turn the ignition to 'ON" position just like any other modern cars.

9. Now, your car should start all the time. However if for some reason, it is now better than before but still like starting 8/10 times, check your ECU for errors. I read somewhere, if the motor mount sensors are out, that could prevent from you starting the car, good time to change to 034 motorsports motor mount sensor delete or replace Original motor mount from VW with sensors.

10. If all the above are taken care of, and still experiencing intermittent starting, probably a hard-reset in few simple step, disconnecting battery, remove from the vehicle for safety, connect car's negative and car's positive cable, leave them overnight. This procedure is believed to reset all ECU and the errors which were stored in, just remember to have your radio codes ready, and you will need to set the dates and times, plus the radio stations. You could probably try this out first before doing the others, up to you.

There is a guy who did a video on how to perform hard reset on B7 RS4, link: https://www.youtube.com/watch?v=LOboWgYjsVQ

11. If the hard reset did not help. I can't think of anything else. Starter motor could be due for replacement.

All the above are based on my experience, I had the same starting issue when I got this car few years ago. I managed to eliminate this by doing all of the above except changing the starter motor and my car starts 99.99% of the time. All the above fixes are somewhat related to starting process, I could have missed a few, but again it was based on my journey.

Best of luck!

vr6geek
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by vr6geek » Thu Feb 09, 2023 11:37 pm

Thank you for the reply KNN! I'm definitely going to check that ground to the starter, as the car had its oil cooler lines replaced due to leaks before I picked it up from the dealership and there's definitely evidence of oil all over the belly pan. I've already replaced the clutch switches and fuel pump relays under the ECU, but I'll be sure to check/replace the starter relays under the dash as well if those are needed.

As far as grounds in the engine bay go, so far I've found:
-single ground wire going from harness under the center ECM, attached to the "firewall".
-single ground wire coming out of the loom going to the throttle body, attached to a bolt in the manifold.
-3 sets of ground wires all attaching to a single point on the body underneath the coolant reservoir.

I'll plan on cleaning all of these connections up along with the starter ground cable. Are there any others you know of that I should hit while Im at it?

Thanks again for your help.

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icyrs4
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by icyrs4 » Fri Feb 10, 2023 4:12 am

Congrats on the new RS4, if you need door blades let me know :)

vr6geek
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by vr6geek » Wed Feb 15, 2023 12:01 am

Okay, I pulled codes again now that I've gotten the car to start successfully. It dies shortly after it starts though. The codes are as follows:

U0100 - Lost communication with ECM/PCM
P0321 - Engine Speed Sensor (G28): Implausible Signal
P0322 - Engine Speed Sensor (G28): No Signal
P2020 - SAE: Intake Manifold Runner Position Sensor/Switch Bank 2: Circuit Range/Perf

It looks like the bad ground was the reason communication with ECM B was lost. I'm assuming U0100 is a stored code to tell you that it lost communication at some point. I'm going to do a hard reset with the battery out and start fresh. Maybe the stored codes are giving me problems? Otherwise, I may be looking at a wiring issue coming off of the G28 Crank Sensor.

vr6geek
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by vr6geek » Sun Feb 19, 2023 6:44 pm

So I don't understand what's happening with this car at this point. I let it sit for a couple of days as I was busy at work. I hooked the battery back up and decided to pull codes again. I had done nothing to the car since the last time I pulled codes. Now instead of 4 codes, I'm getting 7:

P0321 - Engine Speed Sensor (G28): Implausible Signal
P0322 - Engine Speed Sensor (G28): No Signal
P0458 - SAE: EVAP System Purge Control Valve Circuit Low
P2009 - SAE: Intake Manifold Runner Control Bank 1: Circuit Low
P2257 - SAE: Secondary Air Injection System Control A Circuit Low
P0414 - Secondary Air Injection System: Valve Circuit (N112): Shorted
U0100 - Lost Communication With ECM/PCM

At this point I don't know what to do. I'm dumping money into parts based off of codes I'm pulling, then more seem to pop up every time I start to work on the car. This has to be some sort of electrical problem, right? ECM? Alternator? I suppose I'm in over my head at this point and just have to have it towed somewhere. Any experience or advice would be appreciated.

GhiniRS4
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by GhiniRS4 » Wed Mar 01, 2023 9:46 am

Hello vr6geek

I hope that by the time I post this article, you have already solved the problem.

I have also encountered a similar problem where the car does not start smoothly after a few days. Unfortunately, I have not been able to find a complete solution to this problem yet. I have been able to start the car by repeatedly pressing the ignition button until it starts. If it starts smoothly, it usually takes about 2-3 minutes, but if it doesn't, it can take up to 10 minutes.

Although I cannot give you a definitive answer to the starting problem, I can provide some experiences for reference:

1) Idle speed issue after starting: I had an issue with the engine's vacuum hose leaking, which took me a week to locate because the leak was in a difficult-to-detect location under the manifold. Please note that if you smell a strong odor of gasoline or exhaust from the exhaust pipe, this may indicate a vacuum leak.

2) ECU fault codes: Although I am not an expert in this area, I once experienced a similar problem caused by low battery voltage due to leaving the car unused for an extended period of time. After recharging the battery, the ECU fault codes disappeared, and the car returned to normal operation.

Furthermore, I noticed that you have a "Lost Communication With ECM/PCM" fault code. I once experienced a similar issue and almost replaced the expensive ECU. Eventually, I discovered that the problem was caused by a faulty air flow sensor, which was not detected by the ECU. This issue caused the car to stall immediately after starting and prevented it from maintaining a stable idle. If possible, you may want to try borrowing an air flow sensor from a Porsche 997 to see if it helps. It was only after many attempts that my technician and I were able to identify and solve this issue.

I understand your frustration and hope that my experiences can help you in some way.

PS: Currently, my starting issue shows a relay fault code on the ECU, but I have already replaced the relay with a new one. Therefore, I have decided to temporarily ignore it because the car can still start, although it takes a bit of time.

Best regards,

vr6geek
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by vr6geek » Tue Jul 18, 2023 7:04 pm

I figured I'd post an update on how the RS4 is doing:

Right now I have the whole front clip taken off for easier access to everything. As soon as I removed the intake manifold to start in on a carbon clean, I started to see signs that the maintenance history on this car wasn't what it had seemed. The valves were all caked pretty good, and I noticed a decent amount of oil in the "valley" of the engine. I decided at that point that I'd just start from square one and replace every maintenance item I could think of, while also installing goodies from JHM:

-Spark plugs
-Ignition coils
-Sent fuel injectors out to be cleaned and bench tested
-Fuel pressure release valves for both fuel rails
-Valve cover gaskets- also meant buying a new driver's side valve cover due to superseded part, that sucked
-Crankcase Vent Valve
-Valley pan gasket
-Oil check valve and oil jet under valley pan
-Oil filter housing O-rings
-ECS metal oil filter cap
-JHM intake manifold spacers and new gaskets
-JHM lightweight pulleys and 6-rib belt
-JHM upgraded high pressure fuel pumps
-034 engine mounts
-New coolant and power steering reservoirs
-In-tank fuel pump
-Fuel filter
-ECU housing (old one had a super rusted bolt at the rear where water had pooled, and I end up drilling it out to access the ECU)
-obviously fresh oil, coolant and power steering once it's all reassembled. Also AC recharge.

I'm probably forgetting a few things, but I essentially said screw it, let's replace everything and make it a project/learning experience. The spark plugs looked completely shot, and it looked like oil had been seeping from old valve cover seals. All of that seeping oil had made its way into the "valley" of the engine, and on its way down had dirtied up everything in its path. I've spent hours deep cleaning the engine bay and cleaning the carbon off of the valves. The de-flap mod in the intake manifold was done by the previous owner.

Right now I'm waiting on my injectors to come back from testing, and still have pulleys and engine mounts to do. I've heard the driver's side mount sucks, so I'm preparing for that nightmare.

Hopefully once it's all buttoned up the car will run like new, but we'll see. If all goes well, I'll be looking into KW V3 coilovers, downpipes and exhaust, and a JHM tune.

Burty
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by Burty » Sat Sep 30, 2023 5:01 pm

What a horror story... have you made any progress in curing the problem ?

m5killer
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Re: Car Cranks But Doesn't Start. Also Hi, New Owner

Post by m5killer » Sat Oct 14, 2023 4:37 pm

VR6 geek where are you based

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