meathead

1996 A4 2.8l 12 valve
I have been working on getting the car to pass emissions, and after lots of work fixing lots of little problems, I managed to create one.
Car cranks, but dosn't want to start, it sputters, then catches. It idles rough, but seems to run fine otherwise. There are no vacuum leaks, it pulls 15" of vacuum at an idle, and there are no stored codes.
list of things done.
Replace both front O2 sensors
Removed and had my injectors professionally cleaned, and tested, they now measure at factory specifications
Replaces every vacuum hose on the car to eliminate any vacuum leaks
Pulled the intake manifold to clean and test the EGR, and EGR passages
Cleaned the throttle body
Cleaned the MAF (mass air flow) sensor
Replaced the EGR temperature sensor, it wasn’t bad, but was at the extreme low end of passing.
Replace Idle Air Stabilizer valve (idle air control valve for anyone but Audi), it wasn’t bad either, just at the low end of passing
Cleaned all the passages in the crankcase ventilation air path
Replaced all the intake gaskets, and then checked for vacuum leaks around the manifold, and vacuum lines using ether

turbo510

Are you sure that the cams are timed correctly? 15" seems kind of low for idle vacuum in my opinion. Also the fuel pump, a '96 might need a pump (mine has) and won't cause a fault code on its own if it is slow to get up to pressure. How about if you remove the black MAF duct, and spray some starting fluid in? Does it light off on that? And if you have VAG-COM, check the throttle position as reported to your computer, as well as the MAF reading after you get it started.

meathead

I don't know what a good vacuum level should be on this engine, I do know that at high altitude the vacuum levels tend to run lower, but what should it be? I couldn't find anything in the manual on what it should be. I will take a fuel pressure reading, manual says it should be between 55 and 61 psi. I did buy the Ross-Tech software, and it showed the MAF sensor voltage wasn't changing, so I replaced the MAF sensor, that seems to have cured the hard starting problem, but it still runs rough at an idle, rpm bounces about 50rpm. I thought the fuel trim might be worth looking at, but I'm not sure I'm looking at the right blocks.

turbo510

Where are you located, and what is the weather like? I'm in SoCal, morning temps are say 50F, but I noted this morning that my '96 lit off and running within about one revolution of the crank, and yours should too if everything is in order. How about compression?

meathead

I'm located in Denver, it's been in the 20's in the mornings, it seemed to start easier when it was cold, I replaced the MAF (from audi)it seemed to fix the starting problem until last night. I was driving it last night, and it started running really rough. I hooked up my VAG-COM, and it showed no codes, but while I was looking at the MAF sensor readings I noticed the voltage from the ECM was at 14 volts, but occasialaly it would show 4 volts for a second or two, and it would run rough while the voltage was low.
Today I am going to check out the wiring, and see where that leads me.

meathead

wires were replaced about 12 months ago, and plugs at the same time as the O2 sensors