engine skips under boost around 4500 rpm's

[predator247365]

ok i have a 92 talon tsi awd and here lately i notice when i go full throttle under boost it pulls hard to around 4500 rpm's then it starts skipping like it has a boost leak but iv done a boost leak test and have no boost leaks iv rebuilt throttle body ,put new plugs and wires,checked coil,checked vacuum lines no leaks...when i put new plugs in the old ones were brown if that helps anybody i put new fuel filter on and i have a walbro 255 iv lost my cool with this car bout ready to git rid of it can someone plz help me!!!

[steviek]

Originally Posted by predator247365

ok i have a 92 talon tsi awd and here lately i notice when i go full throttle under boost it pulls hard to around 4500 rpm's then it starts skipping like it has a boost leak but iv done a boost leak test and have no boost leaks iv rebuilt throttle body ,put new plugs and wires,checked coil,checked vacuum lines no leaks...when i put new plugs in the old ones were brown if that helps anybody i put new fuel filter on and i have a walbro 255 iv lost my cool with this car bout ready to git rid of it can someone plz help me!!!

What turbo are you running and at how many PSI? It seems alot to me like your hitting fuel cut. Either that or your A/F ratios are way off some other way.

My first suggestion would be turn down the boost and see if that delays the stuttering. If it does then we can assume that the decreased airflow enabled the car to have target A/f ratios longer. That would be indicating fuel cut. Stock 450ccs? No engine management? A likely factor on a aftermarket turbo.

If its a boost leak then the test should have shown it.

[steviek]

Do you have a wideband A/f gauge? or EGT gauge? These will also tell us if the engine is going way lean or rich. Likely lean.

[predator247365]

iv got 550 injectors 16 g turbo no engine management running on maf with cones taken out also have fuel pres reg set on 40psi...i did a pull yest and it didnt skip at all in first when i went to sec and it got to 5000 it did the mild skip again but seems to still pull hard and im running on wastegate pressure

[SilvrEclipse]

Sounds like you figured out your problem. Bigger injectors with no engine management. You need to get a wideband o2 and a SAFC at the bare minimum. By lowering the base fuel pressure you can "scale" the 550s to run like 450s as far as the ECU is concerned with fuel trims and such but this also means your 550s will max just like the 450s did. You need to run stock base fuel pressure and tune the injectors down by a different method.

[predator247365]

thx people im supposed to be getting a afc neo this weekend hope this fixes my problem also got my eye on a wideband ...

[steviek]

Yea and just as a side note. You flow much more airflow in second then you do in first. So its completely understandable that you wouldn't have them maxed in first (too fast for turbo to get all the way up) vs in second.

I have a thread in the tech articles about tuning your a/f ratios with an afc. You should read up before you get started.

Let us know