[Theo]

I replaced my oxygen sensor some time ago.
Had to fabricate the fitting for it to screw in on the new headers.
Question:
Is it possible that the sensor does not go in deep enough and will throw codes?

[Slicktop]

Anything is possible. If it started throwing a code from day one of its relocation then that coud be a problem. If it started throwing a code later then the O2 sensor is probably bad. If you are associating the O2 sensor with your rough idle during warmup remember that the O2 sensor is not a factor during warmup, it does not come on line until fully warmed up and then the efi system goes closed loop. During warmup the EFI system is in open loop operation and does not use the O2 sensor. It takes about 2 mimutes for an O2 sensor to reach its operating temp of 600F. This is a good article on the subject: http://www.autotap.com/techlibrary/u...en_sensors.asp

[Theo]

Thanks that make 100% sense!
Currently at work and try to work out what could be the problem.
So neither could it be the idler jet because then it would idle rough at all times?

[Theo]

Another thing... I removed the water hoses to the throttle body some time ago as well. Our winters don't get that cold here so no danger to that! Wonder if this could affect the temp reading and cause the cold rough idle.
Rough idle I mean it runs constant, then suddenly drops RPM, goes up again and so on.... untill its warmed up

[Slicktop]

The throttle bodies have hot water routed thru them to facilitate faster/smoother warmups. Removing that heat source does your warmup cycle no good.....probably not the problem though.

[Theo]

Pros and cons it helps with performance. The colder the air the better.
The hoses through the throttle body is only to prevent icing up!!

[Slicktop]

Throttle bodies and inlet manifolds are heated in order to warm the intake air which is done for several reasons:

1, Warm air supports smaller fuel droplets, which helps produce a better burn in the combustion chamber.

2, Prevents ice building up in very cold climates due to venturi effect.

3. Facilitates faster warmup.

4. Blocking off the coolent lines does little to facilitate performance because when the engine is fully warmed up the whole engine is basically operating at the same temp due to heat sink, and that includes the throttle body. So even with your coolent lines blocked off the throttle body temp will be at the same temp as it would with the lines in place or at best slightly lower.

5. If there were any real performance gains to blocking off the coolent lines manufacturers would have done it years ago. All they would have to do is put a vacuum operated shutoff valve in the system run by the computer and a temp sensor that would open or close the valve based on temperature.

[VetteAholic]

Originally Posted by Theo

Another thing... I removed the water hoses to the throttle body some time ago as well. Our winters don't get that cold here so no danger to that! Wonder if this could affect the temp reading and cause the cold rough idle.
Rough idle I mean it runs constant, then suddenly drops RPM, goes up again and so on.... untill its warmed up

Should not be the problem. I live in Florida and I did the coolant bypass not too long ago. Car has been running awesome still.

I did it for ease at removing the throttle body when working on the motor. I've messed with the coolant on that C4 too many times already...

[Theo]

Yes the same with me!!
Also disconnected the heater pipes after I have changed out all the hoses. I also put the air inlet temp sensor right in front and "lies" a little with the inlet temp.
But...I still have the rugged idling untill its nice and warm then it purrs....and this only started not too long ago. In fact after I swapped the brake booster and always look at something I might have disturbed e.g. vacuum perhaps?

[Slicktop]

Maybe the brake booster check valve is leaking vacuum externally where it fits into the booster or where the tubing connects to it, or is failing internally..........