90 TSI, Fuel Cuts at Boost, Runs RICH

[98talonchick]

I just got my 90 TSI running yesterday. It idles great, but when i take it on the road, right when boost kicks in, it falls on itself, loses all power, and wont go over 25-30 MPH. All she does is jerk if you push her to go to fast. Its running EXTREMLY rich. TONS of black smoke coming out the back. When i checked the spark plugs they were covered in carbon build up. So i cleaned them off, put them back in, and she boosted AWESOME, and pulled GREAT into 2nd, then the problem came back, started losing power at boost again. Even with the pedal to the floor, she refuses to pick up any speed. The plugs and wires are new. i really think its a fuel problem. I dont know how its running rich but still feels like its fuel cutting....at 25mph. anyone have any suggestions to what the problem could be? Fuel? Igniton>? Wastegate? Runs rich and falls on itself....Let me know..*Dana*

 

[theSicKness]

First thing i would do is a boost leak check. Could be as small as a loose coupler.


Jesse

 

[andymoraitis]

Either a coupler is completely blown off, there's a massive intake leak or your front O2 sensor has shit the bed and thrown the ECU into limp mode while dumping a ton of fuel on top. If you have a cat, look underneath the car after trying to run it. If it's glowing red, the internals have collapsed and won't allow sufficient airflow.

Start with a boost leak test as Jesse mentioned and then move on to the other parts. If you have an A/F gauge (the blinky light show) this will at least tell you if the O2 is cycling. If it's not bouncing back and forth, it's toast.

Let us know what you find,

Andy

P.S. We could also use a mod list on the car since we don't know what's installed on it.

 

[98talonchick]

The only mods done to the car are a turbo XS boost controller, boost gauge, and cat back exhuast. I checked underneath the car after driving it, and no orange glow on the cat. I have a question, if it is the 02 sensor causing problems, what if we completly unplugged it? then would the computer stop getting a wrong signal? or would it continue to dump fuel? We are going to check for a boost leak tomarrow when we have more daylight and time. Then we gotta check out the mass air flow sensor. the old owner of the car said that it drove fine one day, and when he went to drive it 2 days later, the problem occured. Then i bought it.

 

[andymoraitis]

If you unplug the O2 sensor, it'll throw the ECU into limp mode the same way that a failing O2 would. It'll be just as bad as what you have now.

 

[98talonchick]

Well, i figured out what the problem was! The airflow sensor went bad! when my friend unplugged it, we took a drive and it was fine ! it still ran a little rich, but it wasnt falling on itself like it was before. So how much does a new Mass airflow sensor run??

 

[92AWDHX40]

I would check ebay, there are a lot of them there.