My son's 96 2.8L A4 is incredibally hard to start when it has sat for more than about 8 hours. It will crank over like normal, but not catch. Eventually after about 8 or 10 cranking cycles it will catch and it sounds like a 1 cyclinder trying to roll over for about 2 or 3 seconds, then it slowly pciks up rpms and settles out right were it shoud at around 850 rmp. If you touch the gas pedal for the first 10 seconds or so, it will stall or almost stall like its starving for fuel. After that 10 or 15 seconds it will drive fine at all speeds. I have no codes other than a B1S1 O2 sensor circuit code, and occassionally an EGR insufficient flow code. I pulled the FP regulator to see it it holds vacuum and it appears to, although I couldn't get the valve itself to move, or I couldn't tell if it was moving, but the diaphragm did hold pressure, and there was no gas leaking out of it thru the vaccum port. Changed the Fuel pump just incase it wasn't getting enough pressure (thanks Audi for not putting a test port on the fuel rail) but that didn't help either. I'm mostly convinced that it is fuel related, but can't see any obvious issues with anything. Anyone have any ideas?

 

Check the fuel pressure. When you changed the fuel pump, did you also change the fuel filter?

 

Looks like you need an O2 sensor and a good egr port scrubbing but I don't believe either of those codes would give you much trouble starting. The egr really only opens on decel and the port in your intake is plugged anyways. I believe the Lambda system doesn't start working until normal operating conditions if I remember correctly. Some folks have had trouble starting due to coolant temp sensor failure believe it or not. The ecu recieves an improper signal from the sensor and thinks the engine is up to temp which reeks havoc on ignition and fuel trims. Have you done a basic tune up at all? Like the previous poster mentioned, fuel filter and maybe plugs and air filter would be a good place to start.

 

Plugs have been pulled and cleaned up, put back in, they are some kind o platimum tipped Bosch plugs with 3 electrodes so I couldn't tell if they were gapped right. Wires are old and certainly need replacement, but don't affect the running after its started. Air filter is clean, even tried to start it without a filter, no difference. Temperature sensor is new a last year, along with the thermostat, haven't had any temp sensor codes lately. No new fuel filter yet but once started the car runs fine, can be run out on the highway with no misses, doesn't seem to be starving for gas at highway speeds, its just when you try to start it. Near as I can tell by listening all the injectors are working, although one or more could be fouled and not letting much fuel in. Might have to pull of the idle control valve and see if its stuck open letting to much air into the manifold while trying to start. Going to have to get a pressure gauge to check fuel pressure at the rail.

 

Bosch platinum come pre-gapped. How does the car idle? Could he a throttle body issue.

 

Once you get it started it idles fine, and runs fine, the only real issue is getting it to catch while cranking it over. It seems that it is not getting fuel while cranking. I can hear the pump kick on when the key is turned on, it runs for maybe 2 seconds and shuts off. After cranking it will run again for a second or two, I assume its running while cranking, but I can't hear it. I can hear all the injectors ticking with a stethescope when its running, and since it runs fine once started I don't think its an injector issue. Might be a crank position sensor problem but its not setting a code. I ohmed it out and it was around 1050 to 1100 ohms, spec says it should be around 900. Don't know what the tolerance is.

Got a new fuel filter and plug wires on the way, we'll start there, and hopefully I'll pickup a fuel pressure tester this weekend and see what I have at the rail.

 

For what it's worth, when my Passat had an out-of-calibration MAF sensor, the symptoms included periodic CELs and very uncharacteristic hard starting.

 

I'm beginning to think I may have one or more leaking injectors. Started the car today by holding the throttle fully open, like an old flooded carburated car. It didn't exactly start easily, started like a flooded engine, but it did start. Still need to check the fuel pressure at the rail but I've got the gauge, just need to hook it up.

 

Well it's not spark plug wire, fuel pressure or leaking injectors. I changed the plug wires with brand new one, no difference. Checked dead head pressure on the fuel pump and its 83 psi and it holds when the key is off. I had to dead head it against the gauge because I don't have a fitting to get it into the line so I can see pressure when the car is running need to get somekind of T fitting that will fit between the gas line and the fuel rail at the engine. FPR does not leak fuel thru the vacuum diaphragm, and the valve diapragm does move. Pulled the whole fuel line assembly and injectors off the engine, and pressurized the line with the fuel pump. No fuel leaked out of any of the injectors.

 

I keep coming back to coolant temp sensor as I read this. It thows no codes, and can make for some very tough starting. I know you say you changed that, did you get the right one? There is a blue one and a green one. Might even go to the dealer with your VIN to be sure. It takes all of 15 mins to swap....depending on how many times you drop that little plastic clip.

It seems like you've chased down that fuel theory pretty good. And if a blocked EGR was the problem, no 12 valve Audi would ever start.