Audi 100 1990 cold issues

GabrielB · #1 10-28-2011, 08:12 PM

Hello everyone. This is my 2nd thread here. I fixed my oil pressure problem not long ago (was a bad sensor) and now I have problems with the cold start. Problem started a while ago and I thought was because of a defective ICV. I replaced the ICV ( have 2 spares) and nothing. Engine starts ( not as easy as it used to. Need to crank for a few seconds) and idles fine for a few seconds, and stalls if I don't hit the gas. Even pressing the gas pedal, engine runs rough and sputters, and I can smell gasoline out of the exhaust. After 1 or 2 minutes, when it warms up, everything goes back to normal. No more smell, good idle, good response. I checked for vacuum leaks (replaced all small hoses and tested the whole intake with propane. OK), replaced the valve cover gasket (was "wet" with oil) and intake gaskets, new distributor rotor and cap, new wires and plugs, new OEM high pressure fuel pump, new filters, cleaned throttle body and valves, cleaned airflow sensor, checked WOT and idle switches...I even replaced the dipstick o-ring and the DPR o-rings. Tested voltage feeding ICV (getting full battery voltage) and connectors all around. Tested coolant temperature sensor and readings are falling within factory specs for cold/hot engine. Tested O2 sensor and same thing. I'm running out of possibilities here

. I'm sure I'm missing something....Any advise will be appreciated.....

88A5TQ · #2 10-29-2011, 08:13 PM

You will get more views on audiworld and maybe quattroworld.com. I can't personally help you sorry.

GabrielB · #3 10-30-2011, 11:50 AM

Thanks 88A5TQ for the advise. I'll try them. Yesterday I tested everything again following my Bentley manual step by step. I found that the O2 sensor, instead of fluctuating between 0.2 and 0.9v as it should be, reads only 0.24v most of the time, and changes only between 0.2 and 0.34v (cold and hot, same thing. Tried leaning the mix or adding propane, no change). But I was reading also that the O2 sensor does not "kick in" until the engine is warm, and when the engine is cold it operates on open loop mode, with default settings and without the help of the O2 sensor. If that is correct, then a bad O2 sensor should not have anything to do with my cold stalling problem. Anyone can confirm this? Thanks in advance...

88A5TQ · #4 10-31-2011, 08:02 AM

http://www.sjmautotechnik.com/troubl.../10vo2sen.html

You are correct and that website has some good reading concerning all the o2 operations and some testing too.

GabrielB · #5 11-28-2011, 12:12 PM

OK. After a few weeks chasing the problem, I got it finally nailed

. Problem was on the air shrouded system (NF engine, CIS III). The crankcase vent recirculation system put a lot of oil on the intake manifold over the years (I've never cleaned this before). It was awful around the injectors. So what I did is I took both parts of the intake manifold out, steam cleaned everything, replaced all gaskets and injectors o-rings and cleaned the injectors. Also I rerouted the hose from the crankcase vent. I took it out of the intake boot ( I don't want oil on my intake anymore), plugged the hole on the intake and put a breather filter at the end of the vent hose. Working beautifully now. Hope this info helps somebody.