I have a 97 F150 with a 4.2L ,every time I leave home to go to work and I don't let it warm up to operating temp, it backfires out the intake manifold. I've had it to the place I bought it and they have replaced the coilpack, mass airflow and air temp sensors. They have also changed the TPS sensor, and the intake gaskets. After all this they say it may be screwed up because I've had the muffler replaced with straight pipes. At this point Iam ready to trade it in for something different.Has anyone else experienced this or heard of this happening because of straight pipes ?

 

Hey,
I Posted a topic previously about piping a 4.2. Thought the 2 replies I received may be of some interest to you. I believe it's topic #32, just scroll down the screen a bit and click on "Piping a 4.2 with no muffler..." I hope it helps ya.


Snow