hey everybody,
i have searched numoruos times and i still can't find my answer.

so here is my q i recently had obx headers installed along with a custom cat.
i hooked up all the o2 sensors
and reset the ecu

problem while driving down the highway car runs fine. first time i stop or slow down the rpms drop down to zero and the car quits
try restarting car in busy intersection
no luck.

has any one ever had this happen?

So its completely dead right now? First you have to determine if its fuel or spark. Pull out a sparkplug, attach it to the wire and try cranking it and seeing if you have spark. Also do you have a CEL currently? Seems you've only modded the exhaust system and the only thing that would cause something like that is if the new cat collapsed and is choking the exhaust.

*quick edit* just had an epiphany... did you make sure you installed the cat so the exhaust flowed through it the proper way?

just replaced the plugs with bosch platinum
had an aftermarket intake, put stock intake back on
reset ecu still cel

the car runs fine, but if you take it on the highway and drive it at or above 50 mph then come to a red light it just stalls.
and it will keep stalling due to low idle.
check water pump, works fine
car is not over heating


not sure on the cat. how can you tell

With the cat flow thing it usually says it on the cat, at least the one I had bought did.... Get the CEL read and see what is it also.

cel reads
mass air flow sensor has too much air. but I have the stock intake.! reset ecu cleaned mass air flow sensor same thing. is the mass air flow sensor bad. this only happening at warm idle. when I had the exhaust installed I had to extend the 2nd o2 sensor wire by six inches to get it to fit after the cat. before I installed any mods. the car did idle very funny.

https://img.photobucket.com/albums/v...rientation.jpg

Check to make sure your MAF is facing the right way, and that your IAT sensor is installed like it is supposed to be.

yep that was the first thing I checked.

and I will also mention that the car runs fine if I am driving or accelerating. it only stalls when I stop and let off the gas or if the car is moving and I cruise to a stop. tightend up the slack in the throttle cable no diff.

THe IAT is your Intake Air Temperature sensor, it's the only other sensor IN your air intake stream other than the MAF. On the OEM intake, it's plugged into the filter box.

Can you post the actual CODE number of your CEL so we can look at Webtech?

I don't have the code only the description. as follows: MAS or VAS A circuit HIGH INPUT

what do you mean you dont have the # code?

how did you read the cel in the first place? the code is a 4-digit # that starts with a letter (for you, it'll start with a "P")


can you also make sure that you are not getting any misfiring cel codes... if you do, that'll be ignition or injector related