MILs
 

A friend of mine and I installed a BBk Off-Rd H-pipe on my car yesterday, what a job but it was worth it because the flowmasters sound kick a$$! It fired up great, but after driving it a while it will idle really rough and die, even when you go to downshift. We placed the rear o2 sensors back into the bungs and plugged them back up. Now i disconnected the sensors and have the same problem. I think my fuel is running very rich. I believe MILs would solve this problem. Could someone please explain to me how the MILs work???

MIL's just bypass the fact that there are no cats and therefore, the normal engine detector would see that there is an exhaust problem and the "check engine soon" light would pop up. The MIL's bypass that detector, since we all are completely aware that there are no cats.

Something has to be wrong with your car because an offroad pipe will not cause the problems your having. Im positive that you must have disconnected a hose or sensor somewhere on accident. Sounds like something that would happen to me. Go through and make sure all the sensors are plugged up and there isnt a vaccum leak. A vaccum leak should make a whistling noise while the engine is running. Leave the 02 sensors plugged up. They arent the problem im sure. The engine code you are getting does not in any way affect the performance of the car. Thats just the computer saying "hey where did the cats go!?"

your rear o2's are pointless.. mine are turned off. all they do is detect whether or not you have cats, they shouldn't be he cause of what you are experiencing. are you throwing any codes?

i just think that he is running MIL-less.....cause he stated that he thought MILs would solve that problem.....in his case...his computer is reading that he doesnt have cats basically....if u have a tuner, turn off the rear o2 sensors, if u dont buy MILs

yea he is using the senors with no cats - haha thats a problems - get the cheap mils on ebay and fix it.. no prob - but also u ned to put the sensors back it or else you have a major exghaust leak

ok you should plug in the rear o2 sensors.. but the fact that you dont' have cats anymore shouldn't affect your car one bit... it will throw a code though but it shouldn't give you all kinds of problems. i drove around for several months with no cats and my rear o2s plugged in and still on.

Possible cause???
 

There is another factor in the equation to my problem. We couldnt get one of the front o2 sensors to stretch to the connector and we stretched it until it did, could this be my problem???

next time, have a shop do it.. then they have to deal with the problems.

If you stetched the wires to the point that you broke one or more, then yes that could be a cause of a malfunctioning O2 sensor. It would not be the cause of your idle problem in all probability but, the two could be loosely related.

A leaking exhaust or a busted vacuum connection will cause odd idle issues. An exhaust leak would normally cause an extremely rich condition which would foul your O2 sensors pretty quick as you're allowing oxygen into the pipe where you're measuring how much oxygen exists to tune the fuel dump. A vacuum leak makes it almost impossible to maintain proper idle. It will nose dive any time you stop giving it gas. You can release propane (like from a small torch) using a rubber tube to guide it to find vacuum leaks... point the propane around the engine compartment... when the idle improves you found the leak. Narrow it down from there.

Look for black burn/jet marks near all exhaust joints. Once you've found and treated them all (a little white lithium grease helps seal them joints and prevent corrosion), then replace your O2 sensors (just to check) and pull the codes again.

Hope this helps. My bet is an exhaust leak.

Did the pipe come with bungs for the O2 sensors or not. Mine did and I just put the sensors back in the pipe even though I have no cats. I get the check engine light, but its just cuz I have no MIL elims., but I dont have any problems with the way it runs.

Actually if it was a front 02 sensor it would create an idle problem. Those front O2's monitor the a/f on the left and right banks. If one is screwed up, it will make the computer compensate adding or reducing the fuel, which would create an issue with his idle. The rears wouldnt do anything, however.

Make sure you dont have any exhaust leaks as well. That would also cause an issue with your idle being really rough. Check the header connections to make sure you are completely secure. If you have a leak there your front O2's are attempting to compensate for the problem.

You do need to plug those rear O2's in however. Otherwise you have an exhaust leak. All the MIL's do is bypass rear O2's so that they dont throw a check engine light for the lack of cats.

I seem to remember something similar on my h-pipe. The wires on the front 02s weren't long enough. There is a white clip that holds the wire loom for the 02 sensor. Just pop it off and it will free up and extra 1/2 inch of wire. Hope this helps. :banana: