420a motor problems

[Daniel393racing]

Ok let's start here, car starts, idles but here is the thing. When I first start the car and keep it over 4000 rpm the car runs good, builds boost, etc. but once I let off the throttle enough for the rpms to go under 4000. It will not rev any higher than 4 grand, like it has a rev limiter but if I shut the car off then start it again and keep it over 4 the car runs how it should until under 4000 rpms then won't rev any higher until shut off again. WHY?! Please help

 

[grothe3297venge]

Specifics Watson, specifics! What are you tuning with, if anything at all. Have you done a boost leak test? Do you have a wideband, if so what's it reading when it has this issue?

 

[Daniel393racing]

I have nothing to tune with right yet. I guess I should get to a shop and have it done. But I have not done a boost leak test but have check couplers and tubing rather thoroughly everything seemed tight. I do believe the car is running rich, smokes some, plugs are black, etc but if it was a leak I would think the car would react the same every time becuz initially above 4000 rpm the car does what it should. Turbo builds an puts it to use but I don't understand once under 4000 Rpms its back in lower rpms

 

[jayson427]

thats because when you first start your car its in an open loop on the ecu once it warms up it switches to closed and works off of all your sensors. do you have a missing link for the map sensor or fcd?? when you have problems around 4000rpm its a map/tune problem. you need a safc or another way to tune your fuel. you need a wideband first off if you dont already.