Trying to get to the bottom of rough cold start and extended cranking time

[Fastguy]

I just got this car and I'm going through the things I know need done. Pulled air filters and they needed replaced desperately. Pulled all plugs and new bkr7e going in tomorrow. (Wouldn't mind someone mentioning recommended gap here). When I pulled I noticed all had pretty good carbon but tips of electrodes clean. Passenger side of engine, all four plugs had noticeable wet fuel on them and the four driver side did not.

After err I get to the bottom of the rough start and extended cold cranking time I plan to do oil change and full timing belt and accessories.

After doing some reading, it seems like the coolant temp sensor is a likely cause of the symptoms I'm seeing. Is there a measuring block I can look at on cold start to monitor this sensor for a false reading when cold? I would just swap out the sensor to check but don't want to mess with loosing coolant if I don't need to.

[EINHORN]

vagcom

http://www.ross-tech.com/vag-com/

get one, helps with a lot of things

[Fastguy]

Got one. No codes pertaining to rough start

[Bigglezworth]

Ensure your coil packs are working properly and that they are sparking sufficiently. Only way plugs get 'wet' is for unburnt fuel to remain in the cylinder.... That only happens where there is little to no spark.

[Fastguy]

Does it seem odd that one whole side (four passenger side plugs) were all wet? I mean would there be any significance to that?

[mik15]

perhaps running rich on that side? maybe a bad MAF or Lambda? if you get too much umetered air than the Lambda will ask for more fuel....just a thought....

[Dmb408]

Can you describe the cold start more, is it just when it is really cold? If so, my car displayed a certain rough start months before suction jet pump just failed completely on the way to work (on the hwy...wow!).

[Bigglezworth]

perhaps running rich on that side? maybe a bad MAF or Lambda? if you get too much umetered air than the Lambda will ask for more fuel....just a thought....Good point. You will also get a rich bank if you have a bad EGT. When the ECU believes the exhaust gases are getting too hot, it pushes more fuel in to cool the head in an effort to lessen potential damage.

[ben916]

also, how are you starting up?

Are you putting key in and immediately turning over?
Are you putting key in, turn it to on (listening for fuel pump to prime/whine and the headlights dip down then up and all the relays reset)?

It is very curious why one side is wet and not both?!?!

[Fastguy]

also, how are you starting up?

Are you putting key in and immediately turning over?
Are you putting key in, turn it to on (listening for fuel pump to prime/whine and the headlights dip down then up and all the relays reset)?

It is very curious why one side is wet and not both?!?!


Just got the car and started digging into it. Only started a few times. Working on tcu issues simultaneously.

I tried both ways of starting; hop in and start immediately...and...hop in, turn key to on position, sit for 5-10 seconds, try cranking. Same issue. Will crank for approximately 3-5 seconds before it fires up. When it does start it will run very rough and without accelerator intervention the rpm's will dip down and it will stall. If I keep my foot on the accelerator for maybe 20 seconds it starts to even out at that point even though the rpms will still dip down just not far enough to stall. On initial VCDS scan, only codes I pulled were for intermittent crankshaft sensor (which I cleared and has not come back on the few starts), and intermittent coolant fan switch issue (which also did not come back but may after the car reaches normal operating temp again).

As I said, I've only had the opportunity to try this a few times. I'll have a more accurate picture once I've been able to get a few miles on the thing and have more cold starts under my belt. Right now, however, it just drives me crazy listening to this beautiful machine chugging so hard to stay running on cold starts. So far it hasn't mattered the temp (although it hasn't really been above about 30-40 degrees since I've had it).

[lswing]

Fuel filter is a 30-60 minute job, by passenger rear tire.

I was also thinking a messed up lambda or egt could cause the fuel dump to one rail/side.

You could also log injector duty during this startup time and see if one bank is off.

[Fastguy]

thanks. will do the fuel filter as part of the maintenance i am planning once I'm sure the tcu fixes the trans issue. Will do timing belt, water pump, accessory belt, etc. Did the fuel filter on my 2.7 less this last weekend. would have been simple if I would have just had the correct parts. It was leaking so i pulled the banjo bolt off to inspect, installed a new crush washer and it leaked worse. Filter seat was messed up. Turned a 30 minute job into a three hour ordeal. Won't do that again.

[Bigglezworth]

A bad fuel filter would limit supply of fuel vs. provide excess. Spitting and sputtering could indeed be problems with fuel, but with you stating the plugs being wet, that means there isn't a fuel supply problem IMO. Sputtering can also be caused by fouled injectors. A dirty injector will spray incorrect amounts of fuel in to the cylinder. Would be a better chance of winning the lottery though for all four injectors on one bank to do this. Certain to be something linked to control by the ECU to make one side run richer than the other. A scan of certain measuring blocks should certainly confirm the various theroies being presented. Sorry, not much help otherwise.

[ben916]

Yeah, the fuel filter can be a P.I.T.A.


Pulled air filters and they needed replaced desperately.

Not to send you on a wild goose chase:
Since you stated that the air filters were not good, any chance you peeked at the MAFs to see if there is some crap on them also?
Is the Airbox set completely down?

[hahnmgh63]

The MAF's are independent but put a total signal back to the ECU just to keep track of how much total air (each turbo can deliver a little different) is going into the engine since it all gets mixed together in the Intake plenum and all enters through a single Throttle body and into the Intake manifold.

[G2]

Most of the sensors won't matter on Open Loop status (cold engine). The ECT if it had issues, will effect both banks, not just one. But look at comparative values of MAF and 02's.

I'd be looking at the fuel pump, injectors and excessive carbon buildup on the pistons. With the crank sensor code, just replace it.

Wouldn't bother regapping the plugs unless there's a high RPM miss. Keep the gap wide as possible.

Coil packs generally do not cause issues until the engine is at full temp and heat soaked.