Oxygen sensor necessary?

[ruppenduro]

Hi guys
I just finished turboing my b3 but i`m having some issues. I can`t get the car to idle and it won`t rev for beans. I have the wastegate wide open so it shouldn`t be a fuel problem yet.

My question is, do the the ecu's in these cars need a reading from the oxygen sensor? I am running without one. Also, is that sensor on the drivers side of the intake manifold necessary? (I think its for emissions, it had a big vacuum hose going to the factory intake pipe) I have it completly plugged off and the wiring unplugged.

thanks in advance

[kartracer46]

The oxygen sensor is necessary for mixture to be recognized. As for the rest this post needs to be moved to repair section or engine mod section for further direction.

[Pu241]

........As for the rest this post needs to be moved to repair section or engine mod section for further direction.

It has been done!

[SuperDaveGulvak]

A turbo B3 now that's cool just for uniqueness I'd love to see some pics!

[kartracer46]

It has been done!

thank you kind sir! I know it will get the proper attention and response here.

[91_festy_Gl]

With no oxygen sensor the ecu is probably in LIMP mode causing the engine to not want to rev or idle. Your fuel/air ration right now is way off and the engine is running pig rich. Get that sensor hooked back up and she should try to run alot better for ya.

[Pu241]

91 festy Gl, believe you are right about LIMP/default mode, but not sure the O2 sensor is used at idle, I would also check the temp sensor on the passenger side of the intake manifold, green connector, this has caused similar issues with poor running and idling.
Might also check the TPS for correct operation.

[WmWatt]

The ECU may getting conflicting messages. Until the engine warms up it ignores the O2 sensor (called limp back mode as above) because the sensor needs to be warm to work. After it warms up the info from the O2 sensor is used to control air/fuel mix to get maximum combustion. So if your engine is warmed up and the O2 sensor is sending no info the computer will try to adjust but it is pretty obviously out of range. BTW the check engine light should be on telling you there is a problem with the O2 sensor.

Also you can clear the ECU memory by disconnecting the battery. The ECU will use the factory setting for about 20 miles after the battery is reconnected. When the engine is broken in and as it ages the factory settings are no longer optimal so the ECU stores new numbers based on engine performance. You numbers are probably pretty screwed up from disconnecting the O2 sensor. Disconnecting the battery briefly to erase the settings and going back to factory settings might be a temporary improvment.

[zoom zoom]

You turbo'd a 1.3! Thats awesome!

I'd like to see some pics and more info once you get all the bugs worked out! G/l!

[bhazard]

If its anything like a b6t ECU it should be perfectly fine without the o2. It'll run slightly rich but not pig rich. After installing my wideband I found that it would cruise at 14:1 afr. Little rich but not pig rich. It just defaults to open loop.

[iceracerdude]

The guys are right, the o2 sensor will not be sending info to the ecu till it reaches around 600 degrees F. Your car will be correctly in "limp mode" until then. If your using the stock style pcv valve you're probably pressurizing the back sides of the pistons, in other words, pressurizing the crank case. That's not made to hold boost back, it's a pcv valve not a check valve. Also the stock ecu doesn't know what to think when you want to transition from vacuum to boost. When you approach that point (also known as tip in) the ecu thinks it should cut fuel. You haven't done anything to help the computer compensate for that, like adding a thing called a voltage clamp to the 02 sensor.
Show us pictures of what you've done so far, it will help us to help you.

[FestYboy]

guys, you're forgeting about the "sensor on the driver side of the intake" that's been bypassed....

it's your IAC (Idle Air Control), with it bypassed, the car WILL NOT idle properly, you need to hook it back up the way it was before the turbo swap and make sure it's getting metered air from AFTER the VAF.

[ruppenduro]

thanks for all the help guys, right on the money. I went and bought a $14 denso o2 sensor from autozone and mounted it on the downpipe, and also plumbed that big vac hose onto the intake after the vaf meter. Its now holding a nice idle and pulls strong to redline. Running around 5 psi and its roasting the tires in 1st, and a little of 2nd. I just wonder how long this clutch will hold.

Check out the pics here:

http://www.fordfestiva.com/forums/showthread.php?t=38622

[FestYboy]

need to make the VAF level, it doesn't usually like to be tilted on a 90* angle.

[ruppenduro]

thanks, I'll have to figure something out. maybe mount it where the battery is, and move the battery to the trunk.

I was worried about that with the flapper inside