engine backfiring

[brad66]

Just wondering if someone could help me out.I have a '94 explorer and just had the tranny replaced.The problem is the engine now.It ran mint before taking it to the shop.Now it backfires.I took it to an exhaust shop they said everything was put back properly.(Exhaust atleast)I just changed the wires and that helped a little but still backfiring.Just wondering if anyone would know what else you would have to screw with if your changing a tranny.firing order is right.thank you

 

[savagefan]

Maybe they left off a vacuum line either at the mod valve or the tree in rear of the intake.

 

[Vanquish502]

Backfiring usually happens when the plug wires aren't connected to the ignition module properly. On the passenger side, theyre pretty straight forward. Then people do the same on the driver side, which has a different order.

 

[mrboyle]

I agree with savagefan, it sounds like a vacuum leak. I don't see how it could be ignition related if they just put a tranny in (they shouldn't have needed to touch the engine). As far as a vacuum leak, this is very possible. There is a vacuum line that runs from the engine to the tranny, it is very possible it didn't get reinstalled on the vacuum modulator (near rear passenger side of tranny) or at the vacuum tree on the intake manifold (rear driver side of intake). A vacuum leak will cause unmetered air to enter the engine which causes a lean condition and can lead to a lean backfire.

 

[brad66]

Hi,thank you guys for your answers.I have checked all the vacuum lines and plug wires again,and everthing is ok.Today I was driving it and cel comes on after about 20 mins.I hooked up a ford code reader. the koeo test=111,koer=332 insufficient egr flow detected.Like I said before I had the tranny replaced before that it ran mint.I know they had to take off the exhaust to take out tranny.They are trying to say they didn't do anything to cause it to run like this