I have a '95 F250 with a 351W that has GT40 cylinder heads, exhaust headers, and cat-less exhaust with no oxygen sensors, and the EGR port on the intake manifold is blocked off. The truck was set up like this when I bought it. It's running OK but the fuel mixture at idle is so rich it's nearly enough to make you barf. I have a new, remanufactured computer (see my other threads on this site) and I know the ECM regulates fuel mixture but mine isn't t getting all the inputs it expects, like O2 sensor and EGR and I'm guessing this is why the mix is off. So, is there a way for me to manually adjust the fuel mixture?

 

No, there's not. That adjustment is in the PCM and you will probably need to get yours custom tuned for your setup. Sounds like you ended up with someone else's project that they couldn't quite get running right. I wish you luck.

 

Ok, I kind of thought that was the case. Thanks. It runs well enough for what I use it for, which is just to haul stuff to the dump and pick up mulch, so I'll just live with it

 

You need to install an O2 sensor. That is the only way the computer can adjust the fuel/air ratio.

As you have experienced the mixture will go full rich.

 

I would strongly suggest you try to restore an O2 sensor to your system. Without that input, you will constantly be in cold/start/limp mode with the richer setting and your mileage will suffer greatly; to say nothing of the emissions issue. Check to see if at least some of the wiring for the sensor is still there in the harness. If it has been hacked out by a previous owner you could probably obtain what you need from a salvage yard.

dn.

 

Thanks, Donnor. I think the wiring is still there because there's a couple disconnected plugs just hanging in space under the hood. But I'd love to find a picture of what the O2 sensor wires look like just to make sure I'm looking at the right thing.

Where is the best place to put an O2 sensor? In one of the the exhaust headers or in the exhaust pipe somewhere? I don't know where the stock one was.

Thanks.

 

You can put the sensor in the collector of the header. I would pick whichever is easiest to reach the existing wire harness with. I found that you can buy sensors that are the same as stock but with up to an 18" wire pigtail. As I recall, this was from Bosch. This helped me out with long tube header install. My truck uses 4 wire sensors; I imagine yours does too but don't know for sure.

I don't have any pictures, and not sure my 96' OBDII truck would be helpful anyway.

 

Need to get the o2 sensors hooked up, it's so stupid that anyone would remove them....

need a wideband as well to monitor your modded setup, and if you need more fuel you can use an adjustable fuel pressure regulator to ghetto tune to a certain degree. Might want to check if you have one currently, and ensure that it isn't already jacked up.

 

This is based on my 94, but I believe 95 is mostly the same.

The oxy sensor wires run inside the split loom cover that carries the starter cable down to it.

If you replace the starter/hot battery cable (Ford part) the wiring for the o2 sensor comes with it & the plugs for the o2 will line right up in the engine compartment.

My factory Y pipe had a small 6-8" tube that bridged the "Y" & had a bung welded in it for the sensor.

Mulch getter or garbage hauler, you really need the sensor.

 

I saw Scndsin'a post after I took these videos so I'll have to check again later to see if these wires are coming from the starter but at least you guys can see what I'm talking about.

In these videos I point out the wires I think are for the O2 sensors and ask a question about a location for new sensors. Thanks again for your help!

http://www.youtube.com/watch?v=Kc1UuXGq9i4
http://www.youtube.com/watch?v=OcflFD_v7cE
http://www.youtube.com/watch?v=jFMZaGykDMk

 

Tab/Tad solenoid connectors. On your truck there was only one of these solenoids to begin with so one of those connectors was never plugged in. These solenoids are mounted right below where your hand was in the video.
EGR solenoid.
I didn't see any hanging wires in this video. Hint for future reference... use landscape mode.
You want the upstream O2 sensor(or sensors if that applies here) close to the engine so right in those header collectors is perfect.

 

Thanks, Conanski! I traced the positive battery cable down to the starter and there are no other wires running with it as Scndsin suggested there might be. But I'm guessing my battery cable is probably not original. I'll look for a replacement for the stock battery cable and see if putting my eyes on that helps. But even if the O2 sensors get power off a splice into the battery cable I still don't see where they would feed input to the computer? That connection is still eluding me.

 

Oh! How about these connectors? One is in front of the battery and the other is in front of the washer fluid tank/coolant overflow tank. The one in front of the battery looks like it connects to a harness that runs to the alternator.

O2 sensor connection?
O2 sensor connection?

 

Could be, it's the correct connector type.

 

There's a good chance that's the O2 sensor wiring.