2001 Audi A4 1.8t AWM (Avant Quattro)

This car developed a hard time starting when cold recently. Need to crank it multiple times for a long time to get it started. Then when it start's it misses some then clears up. Sometimes when it's particularly hard to start there is white smoke for about a minute or less and the smoke smells like un-burnt fuel, like when starting a flooded car...like the car started rich (i.e. putting fuel in while cranking I suspect).

Low RPM power seems low/slow. The car has been like this for awhile and has always took a few cranks to start but now it takes quite a bit of cranking.
But once over about 1500 RPM car is fine, idles fairly smooth even when cold.

I do not suspect head gasket because coolant levels do not change and it's not smoking all of the time. There is no smell of coolant in exhaust.
I could use a catch can but a plugged up PVC system would not prevent the car to start.
I do not suspect valve stem seals because I've had cars with obvious valve stem leaks and they still start without hesitation even though they puff out some blue smoke for a few seconds.
Oil level is good and the car does not burn oil, so I don't suspect issues with the rings.
Doesn't matter if it's old oil or fresh...same symptoms.

Things that have been replaced recenty:
All new PVC and relating vacuum system valves
All new spark plugs and coils
New camshaft position sensor
New coolant temp sensor

I have a new MAF sensor I'm going to put in tonight.

Just wondering if anyone else has had this issue and if you have any idea what could be going on?

 

I installed the new MAF sensor and performance improved. However, still hard to start when cold. Starts even better hot now..so there is some improvement. It also doesn't seem to take as many cranks to start when cold. So I did an adaptation on the throttle...but that didn't help the cold start issue.

 

Is it throwing codes?

Are you losing coolant?

 

No noticeable loss of coolant.

Recently flushed cooling system and the coolant looked good, no oil.
I also changed the oil recently and didn't see signs of coolant.

It doesn't always blow some white smoke on start up...only once in awhile. But it always hard starts when it's cold.

When I have a hard start and it misses (assuming it misses because it's loaded up with fuel) I get some misfire codes, but the check engine light does not come on. I'll have to scan the computer again to get specific codes.

When it does put out the white smoke on cold start it smells like unburnt fuel. I don't smell coolant.

 

I just found I have a new crank shaft position sensor for this car. Brand new in the box. Going to put that in tonight and see if it changes cold start behavior.

 

Put the new crank shaft position sensor in. Let the car get cold. Took about 10 cranks before the engine would start. So it doesn't seem like it made a difference.

I have not looked at or taken apart the throttle body or any of the associated electronics. Does anyone have any experience or thoughts regarding hard start and the throttle body on this car? It's drive by wire. If it's not putting enough air in during start it could cause the engine to be choked to much, possibly causing fuel to load up. Thoughts anyone?

 

I took out the IAT from the intake manifold and it had a light coating of clean looking oil. I used MAF sensor cleaner on it and put it back in. No change. Before I put it back in I took a OHM reading and it was 2.8k and about 75 degrees temp. I can't find any info on if that's a valid reading. I should note the car starts fine when it's warm. I found a new IAT on-line for about $13 and I'm going to change it. The car has 130k on it and it's likely the original sensor....so let's try that.

 

If it's a cold start problem, it may be something as simple as needing a new battery. Dumping tons of fuel into the exhaust while trying to start it would explain the smoke and a weak battery could possibly cause the cold misfires.

Go to any parts store and have them check your entire charging system. See how that goes.

G/L

 

I did a load test on the battery earlier this year right before I replaced all the ignition parts (coils and plugs) and it's good. Battery is only a few years old. Battery was strong. System charges. Good voltage. Always cranks strong. I don't suspect an issue with the ignition system. I believe the cold misfires are due to fuel loading up, it basically acts like it's flooded until the engine clears out. Then it runs smooth the whole time the car is running. The fact that it appears to be loading up with fuel suggests nothing is wrong with the fuel delivery system either.

Right now I'm suspecting IAT sensor. It could be reading incorrectly at cold engine temp and causing a very rich start mixture. Or, something is wrong with the electronic control of the throttle plate. Not sure how I can test the throttle plate control servo/electronics.

 

Could a faulty evap canister cause this engine not to start when cold?