O2 Sensors? Please Help!!

[Comatose]

86GT 5.0HO EFI, 5spd, PowerChip

Where is the O2 Sensor? I bought a Chiltons repair manual and it states that it's on the rear of the passenger side exhaust manifold(Header). I can't find it. Where is it on an HO?

The car has less than par throttle response, hesitates and surges upon accelerating and pings at low rpms. The pinging came about without changing timing.

The TPS voltage is at 1.05v, very recent complete tune up.

I don't have a Code Tester. Would I be wasting my time by changing the o2 sensor, could it be something else?

Please Help.

[PKRWUD]

You need to rest your TPS to .95vdc @ idle MAX and reset the ECM Pull your codes first (you don't need a scan tool, but they make it easier). Also, try unplugging your EGR and capping the vacuum hose, and see if that makes a difference.

Take care,
-Chris

[Comatose]

The problem I described gets worse the warmer the car gets.

How do I change the TPS voltage? I have loosened the two screws and there doesn't seem to be much adjustment. The adjustment range I had was 1.15v to 1.05v.

To reset the ECM, the pos. battery cable must be unhooked for a number of minutes, correct? Also, I can hear the EGR valve working when the car is in nuetral and revved.

Thanks for the help.

Jeremiah

[shadowblue89]

you should be able to adjust it more than .10v. Play with it a little of moving it clockwise, conter clockwise. You can also move it up, down, left and right that will help lower the voltage. Worse comes to worse open up the hole where one of the screws go in just a little.

As for your battery you can remove the positive cable and it will reset the ECM but my personal choice is to remove the negative cable instead.

Still try and do what Chris said by unplugging your EGR and capping the vacuum line.

[gtsr515]

To answer your question, the 02 sensors are on the H-pipe, yes you should change them after 50,000 miles.

You state you have a Superchip, did you set your base timing to 10 degrees before installation, also low temperature thermostats combined with a chip can cause problems, especially the one with an "octane rod".

The 86 relies heavily on the 02's, MAP, and ACT sensors for control.

Also you state your TPS sensor is set over 1 volt, well, bad news, when the speed density look-up tables see more than 1 volt from the computer thinks your at WOT, adding fuel. Also was your recent tune up done right, crossed wires, etc?

Good luck!

[Comatose]

The complete tune and power chip was just before I bought the car, and yes it was done correctly. The problems I'm desribing have come about recently.

I've reset the ECM and the car idles better (800rpm), but the ping is still there, and it came about without changing the timing.

BTW--Where is the air silencer? Does it help performance?

Thanks for the help.

[PKRWUD]

It's entirely possible that your pinging problem is related to the gasoline you're using. Many gasoline companies change their gas between winter and summer, with the winter gas being more likely to cause a detonation problem. You could try adding an octane booster to see if that solves it, but retarding the base timing a degree or two would be cheaper.

You do use super unleaded, don't you? (it's mandatory with a SuperChip)

Other than that, the O2 sensors are probably due for replacement anyway. Especially if they're original equipment!

Take care,
-Chris

[DZEE'S LX]

If its not fuel I'd vote for the sensors. I need to replace mine also. You will see them as soon as you get under the car.

Consider getting these from Ford. There are many subtle differences in sensors and Autozone etc. will try to cover many applications with one sensor, especially for older model years. I watched the Ford parts guy look some up for a buddy and it was easy to see that it was tricky to get the right one.

Dan

[Mustang_289]

Reading these posts about O2 sensors brings a couple of ??. My son and I are building an 88GT, recently installed MAC long-tube headers - which required extending the O2 sensor wires on the right side of car. I believe these are the original O2 sensors and the odometer is reading 79K. What are some thoughts on swapping out for new O2 sensors? Do they affect performance? Problem I would have going to Ford - is the stock O2 sensors wires aren't long enough to connect up. I've heard some recommendations goto Autozone and take your old sensor and they can match it up with a longer wire - any comments on this?

[DZEE'S LX]

I would still be careful, that Ford parts guy commented that Ford doesn't make it easy to find the right one.
If you want to go to Autozone make them pull out a Bosch book and look it up manually. That would give you more confidence and a good look at other possibilities or a good cross reference. Maybe even find a number to call Bosch and ask them about longer wires.

Dan