Running Rich/Stalling after new alternator

[TurboTalonAwd95]

Hi guys i haven't posted here in a while but i am looking for some input on a problem.

i have a 95 Tsi that i got back from getting the head done about 3 weeks ago. After getting it back i had to replace the thermostat because it would run VERY hot. A few days after that i had another problem. It started with the car stalling when i stopped at a red light. Started up and took off, did it agian and the next stop. Voltage was very low and wouldn't keep a charge.

Fast forward to a couple days ago and i diagnosed the problem as a bad alternator. Got a used, free alternator from a freind. I put it in and it charged but not well, it threw up my battery and temp lights (searching on here again pointed to bad alternator.)

So i put in a NEW alternator and after the install the car runs very rich. My a/f gauge is reading it all the way up. but my AFC is reading no knock or correction or anything abnormal.
It will start and run fine for about 30 seconds to a minute then start to drop rmp's in the 500 range and it will stall out.

My question after searching on here and not finding anything that closely related to my problem is what may be causing this. Now remember that 30 minuted previous to the install with the other alternator in it DID NOT run rich. and would stay running just at low voltage.

Any input or ideas will help. Searching is pointing to boost leak or bad 02 but i doubt it got a boost leak from sitting in my garage for a 1/2 hour.

 

[tindall2006]

I am going to go out on a limb for this, and I want you to know I am not promising this will be your problem, but this sounds simular to something I have seen on a few outboard boat motor's with Fuel injection.


There is a good chance that your charging system has been weakening for a while now, possibly before you last tuned your car. Due to the charging system weakining your fuel pump was not getting as much voltage and giviging you less pressure to the fuel rail (or volume), Now that your charging system is working top notch the fuel pump is working more efficent and giving you more pressure thus allowing more fuel into the engine when the injector's open.

Try retuning a little and see where you are at, granted there could be a million other reasons for this happening.

Do your basics first, check for boost leaks, loose conections, and maybe pull your spark plugs and see what they tell you. I would also suggest a compression test.

It is always good to stick with the basics when you first notice an issue, instead of looking for a more complicated problem. Many times people think a engine is missing because of some major complication, only to find 5 hours later it was just a loose plug wire.

 

[TurboTalonAwd95]

checked everything for being loose or installed wrong. but everything is in right.
Im not shure what else it can be other then something with the fuel system. I turned down the fuel pressure but its still running very rich (althought the a/f is not 100% accurate to go by)
but is still having the stalling problem

 

[Splitpi]

Did you reset the ECU? It'll run poorly till the fuel setting get calculated and set.

 

[blcknspo0ln]

I don't think both are related. Are you using a narrowband AF or a wideband? Don't trust a narrowband for anything.

Secondly, take a multimeter on volts and measure the output of the alternator. It should read ~12-14V when the car is on. Then read the voltage at the battery when the car is on, it should read ~11-12V.

 

[TurboTalonAwd95]

No, i took out the bad alternator and put the new one in a started it up.
how do i reset the ecu and should i play with the safc2 because of the higher voltage possibly running my pump harder and giving me more fuel like tindall said?


EDIT: Narrowband. its a autometer. I know its not completely trustworthy but its still reading it rich where as it wasn't the last time it ran 1/2 hour before.

 

[blcknspo0ln]

No, i took out the bad alternator and put the new one in a started it up.
how do i reset the ecu and should i play with the safc2 because of the higher voltage possibly running my pump harder and giving me more fuel like tindall said?


EDIT: Narrowband. its a autometer. I know its not completely trustworthy but its still reading it rich where as it wasn't the last time it ran 1/2 hour before.

disconnect your batter for 15 minutes and restart the car. Make sure your SAFC settings are for 4 cyl, up arrow, karman

 

[TurboTalonAwd95]

Ok well after resetting it and checking the ecu and rechecking the alt.
My voltage seems to be better. Higher where it should be around 13volts.
i didn't check it with a multimeter because i don't have one but that doesn't seem to be whats causing the rich and stalling problem.

pulled the plugs and they look clean. a little black but not covered.
fuel pressure looks to be in the normal range but i am not sure if my gauge is working correctly. From what i remember it supposed to be filled with liquid but is only filled less then 1/4 and may be misreading?

is there a way to check it without using that gauge or should i just turn it down (have a afpr) until my a/f gauge reads normal? but that may cause me to be running to lean..

 

[TurboTalonAwd95]

I am wondering if anyone has had a similar problem. does it sound like a fuel problem or sensor problem?

After disconnecting my battery and letting it sit and re set agian.
It was running in the rich but went down one bar by bar untill it reached the "stock" level but the went back up?

I turned the FPR WAY down and it ran fine was in the normal zone. But then it started to slowly drop rpms agian and stalled. Now it slowly climbed back up to rich.
I adjusted the Biss but it doesnt seem to do anything if i turn it in or out. Possibly bad BISS?

Edit: didnt mean to bump my thred i was just updating info on it.

 

[blcknspo0ln]

STOP BUMPING YOUR THREADS, it is against the site rules.

your BISS screw allows air past your throttle body and aids in idle control. It does not have a major effect on AFR at idle. If you won't take my advice about disregarding that silly narrowband AFR gauge of yours, than I'm afraid I can't be of help to you.