# Greetings and New S4 Owner, hopefully :)



## aliencurv (Apr 6, 2009)

Hey there everyone,
I'm a pretty big auto enthusiast as a hobbiest . In my collection i have a rebuilt/restored Merkur XR4Ti with T3/T4, a SVT Focus with lowered compression and a GT25R-400, and now a 2002 Audi S4 .
Becuase i'm a circuit designer and hardware programmer (i.e. uber nerd) for my day job, building engine and wiring/designing the electronics comes easy.
Nearly a month ago i purchased my Audi S4 and it had a "stutter" during hard acceleration after 4k rpm . On the purchase we had agreed they will repair the stutter . Their mechanic thought it was the O2 Sensors, so they were replaced.
The stutter continued. Then the car wouldn't start. So they thought the fuel pump .
So now it's been a few weeks while their audi tech looks into it. I usually would walk away from this situation, but i spent too long dreaming about that exact car to give it up. So i told the shop today that i'm coming down to work with the mechanic on the car.
Since i'll be walking into something that i know little about. I was hoping some of you could dump your thoughts to me as to what to check.
Here is what i know.
- There are no diagnostic codes from what i've heard
- The fuel pump isn't getting power
- The motor turns over but doesn't ignite
So i don't know if the S4 is EDIS . But i'm gonna bring my oscilliscope and check the trigger on the ignition coil . I'm also going to use my spark tester on the plug wires . 
I'd like to check with my volt meter that the fuel pump is indeed not getting power . 
They're also leaning towards the ECM being faulty. And due to all the "tests" they've been donig, it could have been damaged by them lol . So I'm going to suggest they take the ECM out of another S4 to try. 
Here are some questions
- Is it a return or returnless fuel system?
- Is there a distributor or is it distributorless or coil on plug?
- Is there an emergency fuel cutoff switch?
- Is there an oil pressure sensor before ECM allows ignition?
- Does anyone have any ideas or experience of what sensors could prevent the car from starting?

Anyway, glad to meet you all! And looking forward to spending some time in this community. Not sure what i have planned performance-wise for the car yet. I'll have to read-up and learn a bit about what "add-ons" i can safely do. This is my daily driver because my other cars are not nearly capable of daily driving.


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## aliencurv (Apr 6, 2009)

*Re: Greetings and New S4 Owner, hopefully  (aliencurv)*

The car has actually been lowered and REALLY taken care of . Which leaves me to beleive that the previous owner probably chipped it also. If that's the case, then i found this thread:
http://www.audiforum.ca/audi-s....html
Perhaps the solder joints came loose on the "chip" . It might be the ECM entirely. I'm going to bring my circuit soldering iron down and perhaps we can fix it right there


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## GLS-S4 (Jun 6, 2005)

*Re: Greetings and New S4 Owner, hopefully  (aliencurv)*

Suggest check the Fuel Pump Fuse. With power applied thru ignition, one can usually hear the fuel pump running inside the fuel tank.
Coil on Plug and no distributor / no wires.
Possible Engine Speed Sensor failure. Engine will turn over but will not start and may not store a code because the engine won't actually start.


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## aliencurv (Apr 6, 2009)

*Re: Greetings and New S4 Owner, hopefully  (GLS-S4)*

sweet thanx for the feedback .
i received a message from another board saying the ecu is chipped . a few things i'm thinking that leads me to beleive that also .
1) the sales guy says he recalls hearing that it was chipped








2) when the MAF is unplugged, the car starts but runs in limp mode
3) when the maf is plugged, bank 2 goes lean and car stalls
i'm gonna check with the obd the maf voltage, make sure it's not the maf .
but if the ecu is chipped, then when in limp mode it will run off the stock limp mode map . when off limp mode, it'll use the regular map . but if the regular map eeprom is only half connected, then it'll behave bad . 
so i'm kinda leaning towards the after market chip not seated correctly or the board being loose, or what have you .. i haven't looked at the ecu yet . going there now to take a look .
PS,
if it's the speed sensor, where is the plug for it? how does the ECU know if the speed sensor is faulty if the car isn't moving? can i check resistance across the sensor to see if it's faulty?
also, even though i'm thinking it's a chip . is there an "ignition module" anywhere? or are the "coil-on-plug" triggers connected directly to the ECU?


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## aliencurv (Apr 6, 2009)

*Re: Greetings and New S4 Owner, hopefully  (aliencurv)*

okay so i've spent the past few hours on this car .
i'm totally confused . so there is fuel . pump is working .
but there is no spark . i took off one of the coils , put in a plug and grounded it . there was no spark .
the obd reader shows 3.5 degrees timing on start . so the ecu is trying to start .
but absolutely no spark . i'm going to look at the mitchel diagrams and see what the schematic looks like from the ecu to the coils . is there anything from the ecu to the coils that could be faulty?


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## aliencurv (Apr 6, 2009)

*Re: Greetings and New S4 Owner, hopefully  (aliencurv)*

hey all . okay i think i narrowed it down to the Crank Position Sensor . Does anyone know where it is on these 2.7's?








thanx in advance!


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## aliencurv (Apr 6, 2009)

*Re: Greetings and New S4 Owner, hopefully  (aliencurv)*

i'm still sure it's the crank position sensor .
the dealership spoke to their "audi tech" who says it is the ignition switch in the steering column . i don't see how the ignition switch could allow the engine to turn over, but not spark . 
well, i guess we'll see tomorrow when they try the new switch


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## GLS-S4 (Jun 6, 2005)

*Re: Greetings and New S4 Owner, hopefully  (aliencurv)*

Ask VAG Forum if it'll read CPS output while cranking?


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## aliencurv (Apr 6, 2009)

*Re: Greetings and New S4 Owner, hopefully  (GLS-S4)*

i'm just learning about this vag-com thing now . i guess one of the audi techs has it . i'd like to play with it . i guess it'll be good to purchase also . 
i'll see if i can get him to hook it up to my car and test for cpk during cranking .
do you know if the audi refers to the crank posision sensor as that? or do they call it an ESS (engine speed sensor) ?


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