Mustang1130

I just put an off road h-pipe and two 40 seris flowmasters on my car and now it is running rich, Please help me determine the problem or let me know what you have done in this situation. Thanks

cliffyk

There's nothing inherent in installing an o/r H or X pipe, assuming there are no leaks before or close after the front O2 sensors, that would make the car run rich.

What is telling you it's running rich?

Mustang1130

well i believe it does have a leak on the driver side right after the manifold, i didnt know that could cause it to run rich si i will have to see if that will fix my problem, i have an obd2 computer that reads emissions and its tell me my car is running to lean. Thankyou for the adivise and i hope it works, Is there anymore ideas as to why thats the problem?

cliffyk

The leak will allow the high pressure leading edge of the exhaust pulse to leak out, and let the low pressure, partial vacuum) trailing edge suck in air--this make the mix appear lean to the O2 sensor.

In closed loop mode the PCM will believe the O2 sensor and try to make the mix richer--via the short term fuel trim (STFT)--to try to get it to 14.68:1. However it can only add +25% fuel (corresponding to a STFT of +25%) before a DTC is thrown at around +30% STFT.

The error desacription will tell you the mix is too lean because that's what the O2 sensor is reporting, but in actuality the mix would have been OK and is now rich because the PCM is trying to fix a problem that doesn't exist...