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B7 2006 RS4 Intermittent not starting problem - weeeeeerid one

mbedford

Member
Hi all, I have a strange Intermittent not starting issue and wondering anyone has any idea on how to fix? Would be grateful.

Around 1 in every 5-10 times, you press the RS4's starter button and it just wont start. No sounds at all (aside from the fuel pump pressuring the system), silent, no ticking, no error lights, the lights do not dim when I try to start it. Plug in a scanner and no fault codes, just silent. Tried different scanners too. 0 current or pending faults. I have a c-tek battery sense checker and the battery voltage is reading well within normal range for a AGM battery which it has. The battery's been reading as high as 80%+ when this issue happens.

If you lock it up and leave it for 5 minutes, then come back, it just fires up like normal. weeeeeerid. No other issues, cars in perfect working order.

It seems to happen more often when the car has been left for a few days, not sure if that's a clue.

I've taken it to Hitech Automotive Centre on Gardeners road in Mascot who are a auto electrician and seem really good in the past, and have a good reputation. They had the car for 2 weeks, tried to start it every day and it started for them each day, and their scanner showed no errors logged. So after 2 weeks they were completely unable to recreate the problem and had to hand the car back.

Starter motor is original as far as I remember, so are solenoids.
Clutch in sensor has been checked as fine by previous mechanic.
I've pulled the starter button out, all connections look good, infact I replaced this with a new one for cosmetic reasons just a few years ago.

I'm not sure what to do to diagnose further as its so hard to recreate the problem and when you do, no errors. I'm reluctant to jump straight in and stat replacing things like starter motor and starter solenoids due to the costs.

Anyone with some electricals experience, I'd be very grateful for some advice?

ideas of what's at fault:

  1. Immobiliser
  2. starter motor or loose connections to it - this thread pointing to starter motor https://www.audizine.com/forum/showthread.php/561861-Delayed-start?highlight=starting+issue
  3. starter motor solenoid - Solenoid is integrated into the starter on this model I've read
  4. Check the heatshield around the starter motor is present
  5. Grounding issue
  6. clutch in sensor - at the clutch pedal
  7. starter relays - under the drivers knee bolster, post here on someone resolving the problem with the starter motor relays: https://www.audizine.com/forum/show...r-cranking?p=13991772&viewfull=1#post13991772 and fuse box diagram: https://fusesdiagram.com/audi/fuse-box-diagram-audi-a4-b7.html
  8. crank-position-sensor
  9. Varta H15 (DIN100L) AGM Battery not good enough?

 
Last edited:
Hi all, I have a strange Intermittent not starting issue and wondering anyone has any idea on how to fix? Would be grateful.

Around 1 in every 5-10 times, you press the RS4's starter button and it just wont start. No sounds at all (aside from the fuel pump pressuring the system), silent, no ticking, no error lights, the lights do not dim when I try to start it. Plug in a scanner and no fault codes, just silent. Tried different scanners too. 0 current or pending faults. I have a c-tek battery sense checker and the battery voltage is reading well within normal range for a AGM battery which it has. The battery's been reading as high as 80%+ when this issue happens.

If you lock it up and leave it for 5 minutes, then come back, it just fires up like normal. weeeeeerid. No other issues, cars in perfect working order.

It seems to happen more often when the car has been left for a few days, not sure if that's a clue.

I've taken it to Hitech Automotive Centre on Gardeners road in Mascot who are a auto electrician and seem really good in the past, and have a good reputation. They had the car for 2 weeks, tried to start it every day and it started for them each day, and their scanner showed no errors logged. So after 2 weeks they were completely unable to recreate the problem and had to hand the car back.

Starter motor is original as far as I remember, so are solenoids.
Clutch in sensor has been checked as fine by previous mechanic.
I've pulled the starter button out, all connections look good, infact I replaced this with a new one for cosmetic reasons just a few years ago.

I'm not sure what to do to diagnose further as its so hard to recreate the problem and when you do, no errors. I'm reluctant to jump straight in and stat replacing things like starter motor and starter solenoids due to the costs.

Anyone with some electricals experience, I'd be very grateful for some advice?

ideas of what's at fault:
Immobiliser
starter motor or loose connections to it - this thread pointing to starter motor https://www.audizine.com/forum/showthread.php/561861-Delayed-start?highlight=starting+issue
starter motor solenoid - Solenoid is integrated into the starter on this model I've read
Grounding issue
clutch in sensor - at the clutch pedal
starter relays - under the drivers knee bolster, post here on someone resolving the problem with the starter motor relays: https://www.audizine.com/forum/show...r-cranking?p=13991772&viewfull=1#post13991772 and fuse box diagram: https://fusesdiagram.com/audi/fuse-box-diagram-audi-a4-b7.html
Varta H15 (DIN100L) AGM Battery not good enough?

How old is the battery?

What is the voltage on battery when you have successful starts?

I’ve noticed anything in the low 11v range and it won’t start.

Have you ever replaced the clutch switch? I think it is blue colour from memory.

I don’t believe it is a starter or solenoid and I would leave them to last on the list due to cost and labour required to change them. They are not really known to fail.

I’ve had experienced issues with exactly what you describe and for me it was a new battery that solved the problem.

I’ve also replaced the clutch switch in the past as well.

I would put a ctek charger on battery for a couple of days to give it a full charge and test from there. If it starts with no issues and then your come back in a week or so and it won’t start, I’d look at replacing battery.

You can do the clutch switch as well which is easy to do. I’ll even change it for you if required.

https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/clutch-switch/6q0927189/

Part number in link if you wish to buy it locally, go get one from VW parts, it will be cheaper than an Audi parts.


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Does sound like battery. You can normally tell by the age.. How old is it?

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I have a similar issue, cold start stored for days is fine. warm start 2/3 times after driving it to a destination I just get a click at the starter. Have replaced the starter, clutch and cruise sensors and the relay under the bonnet. I think because I have the APR kit it fills up with clutch dust and is always flakey. Mechanics cant work it out, but I can always hear the solenoid click and have to sometimes rock it in gear to get it to start.
 
Hi all, I have a strange Intermittent not starting issue and wondering anyone has any idea on how to fix? Would be grateful.

Around 1 in every 5-10 times, you press the RS4's starter button and it just wont start. No sounds at all (aside from the fuel pump pressuring the system), silent, no ticking, no error lights, the lights do not dim when I try to start it. Plug in a scanner and no fault codes, just silent. Tried different scanners too. 0 current or pending faults. I have a c-tek battery sense checker and the battery voltage is reading well within normal range for a AGM battery which it has. The battery's been reading as high as 80%+ when this issue happens.

If you lock it up and leave it for 5 minutes, then come back, it just fires up like normal. weeeeeerid. No other issues, cars in perfect working order.

It seems to happen more often when the car has been left for a few days, not sure if that's a clue.

?

Not sure if this will definitely be the solution for you, but it is definitely worth a try...

All of the symptoms you have described are also exhibited by a failing 'crank-position-sensor' (on the gearbox at the flywheel, plugged into part of engine loom).

Crank-pos-sensor (CPS) does not fail in a binary fashion where it just stops working... instead it slowly dies, and when it begins to slowly be on its way out, you will try to start your car and it wont the first time, then it will start...

as the sensor keeps getting worse, it takes more and more tries before the car starts, and then one day it just wont start for many turns of the key (or pushes of the start button) and then eventually start, then at some point after that it just will not start period.



I have had this happen on more than one audi, both manuals that had the crank-position-sensor at the flywheel...

both times problem was resolved by replacing the 'crank-position-sensor', ie car starts every time perfectly after this.

Also, they do not throw a fault code until very close to complete failure, so you will have the difficulty starting getting worse and worse for quite a while with no fault code to point to the crank position sensor. I had no fault codes in both instances.


Again, this may not be your solution but if it hasnt been tried yet then i suppose it could be worth a try?
Worst case you will have a new, fresh CPS as they all eventually fail in the same aforementioned way.

good luck either way


PS - also check to confirm that the factory heat-shielding is present around your starter motor (rs4 v8 has a small dedicated OEM heat shield around the starter motor), as i have read some threads on audizine where the heat-shield wasnt fitted back after needing to be removed for whatever reason (servicing, part-fitting etc) and starting issues ensued (presumably from radiant heat compromising the starter motor mechanically), and once the heat shield was re-fitted around the starter motor the issues went away.
 
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How old is the battery?
What is the voltage on battery when you have successful starts?
I’ve noticed anything in the low 11v range and it won’t start.
Have you ever replaced the clutch switch? I think it is blue colour from memory.

Was new in 18/11/2020 so approx 1.5 years old. Type = Varta H15 (DIN100L) Start/Stop AGM Battery - 36Month Warranty (42 Months in non Start/Stop vehicle like the RS4).
Clutch switch was checked or replaced (cant remember which) by an old mechanic I used to use he said, I not sure he did, I dont use this mechanic anymore.


Not sure if this will definitely be the solution for you, but it is definitely worth a try...
All of the symptoms you have described are also exhibited by a failing 'crank-position-sensor' (on the gearbox at the flywheel, plugged into part of engine loom).
also check to confirm that the factory heat-shielding is present around your starter motor (rs4 v8 has a small dedicated OEM heat shield around the starter motor)

Will add crank-position-sensor and check the heatshield around the starter motor to things to check.


Any update?

It did it again yesterday, so will get it booked into Hi-Tech Automotive again after Easter.
 
Edit: Issue returned shortly after.

I've just changed out the crank position sensor, and there was probably nothing wrong with it, but it seems to have done the trick. It had a bit of build up with oil/grease and some metal shards on the end as it's magnetic. It's started fine around 20 times today so I'm hoping that's my fix. I have a Sachs racing clutch so get a fair bit of dust in there and also inside the starter motor. Hopefully this helps someone else as I've been chasing the issue over a year. 20230710_134120.jpg
 
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Update, and solution found.
Diagnosed and found starter relays were not right, so replaced, but didn't fix.
So found a new starter motor online, as Audi Aus wanted nuts price, and got it delivered and workshop installed it.
Problem all fixed, and the new starter seems to have a bit more 'pep' in its urgency when it starts.

Work all done by Gary at High Tech automotive, Gardeners road Sydney. Opposite Porsche Sydney South. Would totally recommend them!!
 
Update, and solution found.
Diagnosed and found starter relays were not right, so replaced, but didn't fix.
So found a new starter motor online, as Audi Aus wanted nuts price, and got it delivered and workshop installed it.
Problem all fixed, and the new starter seems to have a bit more 'pep' in its urgency when it starts.

Work all done by Gary at High Tech automotive, Gardeners road Sydney. Opposite Porsche Sydney South. Would totally recommend them!!

Great to hear you got it sorted finally.


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Agghhhh spoke too soon! after it starting well about 15 times, its done it again :(
Press the starter button, and a single quiet 'tick' sound, and nothing, no errors. Not sure what next thing is to try. I really thought we had this fixed with the new starter motor installed.
 
Ouch, not good.

So working backwards.

What hasn’t been replaced?


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So frustrating when this sort of thing keeps happening. Did your mechanic confirm the heat-shield around the starter was also present?

Not sure what next thing is to try.

Did you try the 'Crank Position sensor' (G 28) yet?
 
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Hi all, just wanted to update. Hi-tech Auto replaced the battery with another AGM type, and after 6 weeks, driving it twice a week, it's started every time.

It's strange as the previous Varta AGM battery was all within manufacturer specifications for this model car, only 3 years old, and had a good voltage, always was kept topped up.
 
Wow, that’s the easiest fix you could ask for & one of the most frustrating to find.

I hope it resolves the issue & is fixed for good.


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Modern cars, especially those with battery management systems can be very sensitive to battery types. It's for this reason I've always gone with the OEM battery when I've had to do replacements in the past.
 
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