I have a 97 Z28 M6, I recently put on a set of Jet Hot Long tubes with no cats. I didnt get O2 simulators, i dont drive it every day but i drove it probably 500 miles within a few months and now after about 4 or 5 miles it starts to cut out a little bit when i give it gas. Could be alot of things, Opti spark maybe? can anyone give me some clues????

 

Might want to check your plug wires. It's not uncommon to end up toasting one or two after a header install. Depending on what brand header you have. Some put the tubes in VERY close proximity to the wires.

 

I'm curious. How is it able to run without O2's?

 

I have o2 sensors, not simulators. but the weird thing is that i can drive it for 4 or 5 miles before it starts to act up.

 

You may be getting your stumble when it warms up enough to go out of open loop. Besides checking for burned plug wires like 96CamaroSS suggested, check the O2 sensor wires too. If one is damaged it could cause the miss when the car warms up enough to go into closed loop.
Any codes? Autozone, etc, can scan it for you.

 

If you have not installed any cats on the car and with standard O2 sensors( no simulators) the computers is seeing a really rich state of condition due to no cats to clean up the exhaust. In return the computer is probably trying to lean the fuel mixture out and when you get on the gas it probably tends to stumble because it is lean and takes a second or so to richen it up because it sees the TPS angle grow and it knows it need to supply more gas. I would recommend getting the simulators asap before it leans itself too much and you hurt the motor.

 

OBDII uses the second set of O2s for monitoring the condition of the cat but has nothing to do with fuel enrichment. The front O2s are for that. Also the "cats" do not clean up rich exhaust.

More than likely you screwed the front O2s or you burned a wire. Check all the wiring for the O2s carefully. Then scan it for codes and reset them. See if a code returns. More than likely you will have to replace one or both of the front O2s. Many have lost them from installing them BEFORE they ran the engine for a while to "cook" off what was coating the inside of the headers. While others were just careless when they installed them and simply burned the O2 wiring.

 

Agreed, front O2s are most likely the problem. When you first start the car up, the PCM will run in 'open loop'. In open loop, the O2s are not being used for standard fuel mixture settings. After the car warms up and you drive over a certain mph, the PCM switches to 'closed loop' and begins altering the mixture based on O2 sensor readings.

As a previous poster stated, the rear O2s are only used to predict cat failure/efficiency. They do not have any bearing on fuel mixture. You could unplug them alltogether and the fuel mixture would be the same (although you would thow 2 codes).

The O2s are pretty sensative. When you swapped out the exhaust, you could have just layed the O2s down on something which contaminated them causing them not to read correctly anymore.

Are you getting any codes (Service Engine Soon light)?

Thomas.

 

The speed of the vehicle has nothing to do with switching from open to closed loop. The vehicle will switch even if it is sitting still and never moves.