1G runs rich when ever let off of the throttle

[cbellsondsm]

My late 92 tsi stalls when ever i let off of the throttle and put the car in neutral to coast. I cant seem to figure out what would cause this. I have tried many things.

Mods
t3/t4 v-trim turbo
SBR manifold
Apex 3-inch turbo back
Evo 3 o2 housing
650cc injectors
Walbro 190 fuel pump
S-AFC
Datalogger
full intercooler piping
big side mount intercooler
act2600
2g mas
key diver eprom chip

This is what i have tried doing so far. Changed ISC motor, changed throttle position sensor, cleaned throttle body out, put back on 1g mas, put back in 450cc injectors, and swapped a different stock ecu into my car. Nothing seems to stop it from running rich when ever I slightly let off of the throttle which is what is causing it to stall. Putting back in the 1g mas did help with the problem but didn't fix it. As the car doesn't stall as easy but on the datalogger i can still see that it is running rich when ever i slightly let off of the throttle. Could the throttle body just need to be changed? Could it be the turbo flowing to much? Could it be a vacume leak? Please help me!!!

 

[notractiongst]

Blow off valve is recirculated right?

 

[cbellsondsm]

Yes i am recirculating. Also something i forgot to add. The car runs great starts easy, accelerates fine, and cruises fine. Its just when ever i slightly let off of the throttle it runs rich and will die out if i put it in neutral. I can then start it and it will clear itself out and then idle fine.

 

[ltho98]

Uhm, how can you tell you're running rich when you off the gas? If you are going off o2 volts than thats a bad call-- for about a zillion reasons.

What does your low-throttle correction look like at all the rpm ranges?

You could be going way way way lean too.

Try one extreme then the other and see if it helps

 

[cbellsondsm]

I was going off of the o2 fuel trim and also you can smell the richness in the exhaust when this happens. So i know it is running to rich when i let off of the throttle.

 

[ltho98]

o2 fuel trim????

Ok, lets assume you didn't read vfaq.com and i'll just copy/paste straight from there for you:

"Fuel trim" in the ECU is the ECU's method of tuning individual cars.

In theory, the ECU reads the amount of air entering the engine via the mass airflow sensor (MAS) in the air intake. It will then add the proper amount of fuel through the injectors, ensuring a good burn, low emissions, etc.

However, while that works in theory, it rarely does in practice. MAS sensors vary, even when calibrated, even if only due to age. Injectors become clogged, fuel and turbo pressures can vary, parts wear or are replaced.

The way to compensate for the individual car-to-car variations is through fuel trim. By checking the oxygen sensor, the ECU can "check" if the amount of fuel it added was too high or too low. It will then add or subtract fuel in small increments depending on what it "sees". It "remembers" these adjustments and averages them over a period of time, resulting in a "trim" factor. The fuel trim is constantly applied and adjusted.

There are three fuel trims on DSMs: low, medium and high. These refer to the mass of air entering the engine, and only roughly correspond to RPM ranges. Low applies mostly to idle (750-1000 RPM), high in the 3000-4000 region, and middle in between.

Users of Super-AFC and similar units usually try to adjust their AFCs so the fuel trims are near 100%. This is mostly to provide a baseline of settings for future tuning - it means the AFC settings are "fooling" the ECU into "thinking" the car is still stock (or near stock). It also allows the ECU a lot of range to adjust the fuel trims as necessary.

Fuel trims have no effect at open loop (high RPM or hard accelleration). In this situation the ECU is ignoring the oxygen sensor and there is nothing to trim. Datalogger owners will see their fuel trim "stick" at 100% in open-loop situations.

Those interested in the details of DSM datalogging may find the Pocketlogger FAQ and Technomotive's Datalogger 101 guide.

Ok, now that we have semantics out of the way.

What are your low-throttle fuel trims at and what does your low-throttle correction look like?

 

[cbellsondsm]

The low fuel trim when cruising sits around 100%. Then when I let off the throttle and put it in neutral the o2 fuel trim drops to 38% and the low fuel trim starts to drop as well. Then a couple of seconds after idling the engine clears out and the o2 fuel trim rises back up and cylces around 100% along with the low fuel trim. The mid and high fuel trims sit around 85%. This was with the 2g mas 650cc injectors and keydiver chip. The correction percent I was using was -8% at 1000rpm -7%2000rpm -8%3000rpm
-8%4000rpm for the low throttle point. As of now the with the stock injectors, mas, and stock ecu the low fuel trim is around 120% and both the mid and high fuel trims are at 100%. I don't have any clue as to why it would suddenly run rich when i let off the throttle a little bit.

 

[ltho98]

For me.

I'm on a 2g mas, 650cc injectors and i'm running about -15 across the zero throttle back in my AFC days

However, now I have an emanage that makes things nicer as i have an independent anti-stall map which feeds the ECU any value i want below a certain throttle point.

 

[cbellsondsm]

The weirdest thing happend last night when i was driving home. My car started to hesitate and stumble while i was cruising down the road. When i came to a stop at the intersection it stalled. I could start it back up but then after a second it would just stall again. I tried starting it like 3 times and everytime it would just fire up for a second then die out. All of a sudden my check engine light came on. I checked the code and it was code 44(ignition coil). I tried starting it one more time and i got the engine to rev to 3000rpm i held it there and took off not letting the rpms drop below 2000 the whole way home, but then after five minutes of driving it drove fine like nothing ever happend and the check engine light went off. So is the coil starting to go bad and maybe my car is getting weak spark and that is what is causing it to die out or run rich when ever i let off of the throttle? Or could this have just been some sort of a freakish thing and now my car runs fine?

I changed the ignition coil and it still does runs rich and stalls when ever i let off the throttle slightly. If you have any suggestions please let me know.

 

[missouri_dsm]

check for boost/vacuum leaks. Also your cat could be clogged. Wouldnt hurt to change plugs and wires. Maybe your 02 sensor is going bad. Also whens the last time you changed or cleaned your air filter?

 

[cbellsondsm]

I just changed my plugs, put a brand new k&n air filter on, and i am not running a cat. So basically i have narrowed it down to the throttle body, or a vacume leak of some sort.

 

[c5chris]

Im on 100% rich on my narrowband PERMANENTLY after I cleaned my K&N and double-checked my connections.

I changed my 1st o2 sensor and im now cycling back and forth from stoich to rich depending on position of accelerator.

 

[Turbo Talon DL]

Your shits stalling out like mine used to do..it happened to me on the freeway in rush hour traffic tho It was my FPR. It was stuck shut. Check that FPR.