Intermittent starting issues

[audiv8]

Hey guys,

So my S is having a weird starting issue. This has happened to me twice now and I would love to find this gremlin.

First incident - I was at work car was sitting for about 5 hours from the morning commute. I drove to the post office (5 miles), come back out and the car wont start. I had about 3/4 of a tank of gas. After sitting for about 30 minutes and me checking the fuel pump and ECU fuses the car starts right up fine and drives like nothing happened

Second incident - Car was sitting for about 3 hours. Go to start the car and it wont run. about 3/4 of a tank. I let it sit overnight went out in the morning and the car started right up.

The car just cranks and cranks but wont start, like it doesn't have any fuel. All the correct lights are up on the dash(EPC,Check engine, ABS,etc).

I just got a vag-com and am new to the whole data logging process. I read this article and am familiar with the process.

My question is, what are the best data blocks to record once my car decides not to start again?

Specs:
2001 6-Speed, GIAC Chip, Samco TBB, 710n's about 85k on the car.

Thanks much,
-Jimmy

[audiv8]

So I just scanned for codes and this one is caught my eye.

16706 - Engine Speed Sensor (G28): No Signal
P0322 - 35-10 - - - Intermittent

After looking at the ross-tech wiki i am going to replace this and see if I still have the starting issue. Is this the same as the crankshaft position sensor?

Thanks

[h3lp_c0mput3r]

I just had the same issue happen to me yesterday. The car just cranked, it had plenty of juice in the battery, but it seemed like there was no fuel. It finally started after I tapped the gas petal a couple times while cranking. I'm having my car checked out tomorrow. Let us know if replacing the engine speed sensor fixes the problem. thx

[audiv8]

yeah let me know what it is in your case. By any chance did you pull any codes before bringing it to the shop?

[audiv8]

So i decided to go ahead and buy the speed sensor. I got it for 47.67, not to bad. Hopefully this fixes it.

Stay tuned.......

[casawhites4]

my car sometimes wont start, but it wont even crank...then i wait a few secs. put the key in and out and press the clutch a few times, and boom it starts. what can that be?? no codes as of monday.

[infinkc]

Have you replaced your ignition switch? they are known to go bad.

[kengvang]

yeah my ess just went out on me too. were did you get yours for $47. i bought mines through 034 for $125 shipped.

[audiv8]

I called the dealer (Audi of Burlington, Burlington Ma) and told them I needed a speed sensor for a 2001 Audi s4. Gave the guy the vin number and this is the quote I got. I asked him if it shows where it is on the car, he said right near the drivers side front axle, so i assumed it is the right part.

I just looked on 034's site for the speed sensor and couldn't find it. Are we talking about the same sensor?

Just an update went to leave for work today and the car wouldnt start, same exact issue. I left it there gonna scan it tomorrow before i go in. Are there any specific troubleshooting steps I should try? Suggestions?

I ordered my Bentley manual yesterday from ross tech. Hopefully that will give me a better idea of the install.

Thanks,
-Jimmy

[audiv8]

Got into work this morning and she started right up......

This car is got a mind of its own :)

[h3lp_c0mput3r]

codes came up as the speed sensor switch for me. I'm going to replace mine. where is it located? I want to figure out if this is a DIY job.

thanks

[audiv8]

from what I have read on here it is located on the drivers side of the car. Right above where the half-shaft goes into the trans.

Am i correct on this?

My Bentley manual will be in by this weekend. I will post a more accurate info once I get it setup :)

-Jimmy

[SLC_S4]

By chance have you recently had any transmission/clutch work done?

[audiv8]

no, none at all.

Just picked the part up from the dealer. Looks exactly like the one i have seen in a few posts on here. Hoping to install it this weekend. I will keep you guys updated.

-Jimmy

[h3lp_c0mput3r]

your location sounds correct from what I have read too. Can you post some pictures form the bently manual or from under the car when you do it. It sounds like a really easy job, I'll be doing mine this weekend.

[vorsprung00s4]

The car just cranked, it had plenty of juice in the battery, but it seemed like there was no fuel. It finally started after I tapped the gas petal a couple times while cranking.

why would a speed sensor have anything to do with a problem like this? (I'm having the same problem)

my car will start up fine when it's cold or if it's at full operating temperature, but if i leave it and it cools down just a little bit, then i have to pump the gas pedal to get her to turn over.

[SLC_S4]

why would a speed sensor have anything to do with a problem like this? (I'm having the same problem)

my car will start up fine when it's cold or if it's at full operating temperature, but if i leave it and it cools down just a little bit, then i have to pump the gas pedal to get her to turn over.

It's the engine crank sensor, but also called the speed sensor, it doesn't measure vehicle speed, but the engine speed.

Edit: Just saw that you highlighted a specific part of the quote that yeah, really wouldn't have anything to do with this sensor.

[casawhites4]

Have you replaced your ignition switch? they are known to go bad.

really, does that sound like my problem?? never heard of that...

[S4 Dan]

my car sometimes wont start, but it wont even crank...then i wait a few secs. put the key in and out and press the clutch a few times, and boom it starts. what can that be?? no codes as of monday.

theres a sensor that senses when the clutch is pressed in... seems like your issue. It wouldnt throw any codes, and it has no purpose of being there except to make sure the clutch is pressed in when you start the car. You can drop the dash and simply jump the wires(wouldnt recommend) or you can go to audi and pick up a new one.... Not sure how much it would run you, but it cant be too expensive. The switch is the size of a quarter maybe, and is a simple momentairy switch.

As for the OP, my guess would be bad crank sensor. Which i would imagine is the same as an engine speed sensor. Either way, good luck, and i hope you figure out your problems

[S4 Dan]

p.s. - i dont beleive its the ignition switch.... it would happen way more often, and your car would likely shut off while you were driving, ect...

[h3lp_c0mput3r]

Originally Posted by h3lp_c0mput3r View Post
It finally started after I tapped the gas petal a couple times while cranking.

Edit: Just saw that you highlighted a specific part of the quote that yeah, really wouldn't have anything to do with this sensor.

to vorsrung and SLC,
I'm not sure if it tapping the gas really help the car start or not, it was the only thing I did differently after several attempts to start the car within 10 minutes. I do know that the engine speed sensor is bad though, I was getting the same codes as audiv8, I had the problem diagnosed at the dealership and they said my g28 engine speed sensor is bad.

I had been experiencing some weird hesitation and rpm just the last couple of months, I thought that it was my clutch going out, but now I'm thinking that those issue might be related to the engine speed sensor too. Hopeful those will go away once I get this taken of.

Anybody know where to get this sensor cheap? I check 034 too, but couldn't find it on their site.

[SLC_S4]

to vorsrung and SLC,
I'm not sure if it tapping the gas really help the car start or not, it was the only thing I did differently after several attempts to start the car within 10 minutes. I do know that the engine speed sensor is bad though, I was getting the same codes as audiv8, I had the problem diagnosed at the dealership and they said my g28 engine speed sensor is bad.

I had been experiencing some weird hesitation and rpm just the last couple of months, I thought that it was my clutch going out, but now I'm thinking that those issue might be related to the engine speed sensor too. Hopeful those will go away once I get this taken of.

Anybody know where to get this sensor cheap? I check 034 too, but couldn't find it on their site.

I don't know if $95 is necessarily cheap, but it's available from JHM:
http://www.jhmotorsports.com/shop/ca...products_id=94

[h3lp_c0mput3r]

nice, thats cheaper than the dealership, they want $135. thanks

[audiv8]

Just to add to this, the last time my car didnt start i tried pumping the gas and that didnt help at all. Let me open this can of worms.... does pumping the gas when your are trying to start the car even do anything since the introduction of fuel injection?

Just checked the tracking info on the bentley, it will be here today. I will take some screen grabs and send them over to you(h3lp_c0mput3r), pm me your email address.

putting this part in tomorrow so i will let you know what i find.

-Jimmy

[SLC_S4]

It really sounds like the engine speed sensor.

[jay340S4]

i am also having similar problems. I just recently bought my 2000 S4 and everything was fine. But the last few days I have been driving it and it stalls and then won't start. I let it sit for about 10 minutes and then it starts like nothing happened. Am I having the same issue as everyone else or is it something different. Any ideas?

[SLC_S4]

Sounds like the same issue. What does it do after it stalls and you try to start it again?

[audiv8]

jay340S4,

Try to get a hold of a vag and see if the same code comes up from my original post. Chances are its probably it.

[audiv8]

All great site: www.vagcat.com It has some nice diagrams.

Speed Sensor is number 20 right?

-Jimmy

[h3lp_c0mput3r]

good find, I think you are right. Looks like it sits in front of the drivers side front axle, at the very front of the transmission case, near the fly wheel.

[jay340S4]

When it stalls and i try and start it, it just turns over but won't fire up. Pumping the gas does nothing to help start it. Just turns over. But it i let it sit for 5 to 10 mintues it fires right up. Also I have been watching the temperature gauge to see if there is any weird jumping around with the temp and it seems to move quite a bit. When I have been driving around giving it a little gas here and there, it sits about half on the gauge. When i am just going slow it drops down a fair bit. Does that mean anything or is that normal? I would love to hook a vag up to it regularly but unfortunatly the closet one to me is 500 miles away and nobody where I live wants to touch the car. The guy I bought the car from is coming here with one so we will see what it says.

[audiv8]

Here are some pictures from the install. Sorry for the quality they are from my phone.

The open hole is where the sensor goes into the tranny.


Heat shield that you have to take off to get at the sensor.


Old sensor on the left, new is on the right.


Here is is installed. Note the plastic clip on the right.


Couple things to look out for. Watch out for the cat when you are working on getting the sensor out. I burnt the sh*t out of one of my fingers, didnt realize it was right there. Also the screw on the top of the heat shield is a PITA, i used a couple extensions on the end of an hex socket. All in all it wasn't that bad.

I cleared all my codes and took the car for a nice drive scanned again and the engine speed sensor was gone. So i guess will see what happens.

-Jimmy

[jay340S4]

I have noticed a pattern with the stalling, it always happens when the temp gauge is at half. Sometimes it stalls, then sometimes when i turn it off and try to start it right away it takes a few minutes to get it going.

[kengvang]

so did that sensor fix the problem? how hard was it to replace? was yours a 6 speed or auto?

[audiv8]

So far so good. I am going to scan the car when I get home from work and see if the senor error shows up.

I would say a 5 on a scale of 1-10. The biggest suggestion is to make sure the car is cool before you start working. I burnt my finger pretty good on the cat. My car is a 6 speed.

[h3lp_c0mput3r]

I ended up replacing a different sensor than you. This is the one the dealership said needed replacing. Hopefully this fixes my starting issue, hesitation and weird rpm jumps. The car is definitely running a lot stronger with the new sensor in. It must have been bad for quite a while, because I don't remember it pulling this hard since I have owned the car. I haven't had a chance to check the codes again, I'm going to try later in the week

this is the sensor, someone posted a link to it, but it's a different one than audiv8's


it's located behind the engine on the top of the transmission


follow this plug, behind the coolant reservoir


one bolt holds it in place, pretty easy to remove with a long extension and 10mm socket

[audiv8]

Soooooooooooo,

I was driving to work this morning just sitting in wonderful Boston traffic and my car just died. At first I thought i had stalled the car but I was in neutral. I quickly tried to turn the car back on but it would just crank over and not start. I had to push the car to the side of the road and after about 5 minutes the car started right up and i drove all the way to work without any other issues.

This is so frustrating.

Anybody else have anything to add?

h3lp_comput3r - What is the name / part number for the above sensor? cam position sensor?

Thanks,
-Jimmy

[h3lp_c0mput3r]

It is the g28 engine speed sensor, part # is 06A-906-433-C, some times also referred to as the crank sensor

its the one that SLC_S4 linked to.
http://www.jhmotorsports.com/shop/ca...products_id=94

I picked mine up at the dealer for $135 because I didn't want to wait for shipping, but $95 is a good deal if you can wait for it.

[audiv8]

Cool,

I am thinking this might be the culprit, I am going to vag it when I get home from work and see what I find.

h3lp_comput3r, do you remember what this senor showed up as when the dealer scanned it?

Thanks

[SLC_S4]

I am almost certain the engine speed sensor is your problem. Shouldn't be too difficult to replace yourself.