Removed O2 Sensors

[rad23racer@hotm]

I am working on a 94 Mustang that is running in the Camaro-Mustang Challenge (NASA.) The car has been running for a couple years but recently started having problems with a high-rpm miss. I just saw the car for the first time yesterday so all the history is hearsay.

The plugs were very black and some had fuel fouling when I pulled them out. The plugs being used were 4 prong platinums. I replaced them with new Bosch Copper (on hand and free) as I have heard that some ignitions can't handle the increased gap and higher resistance of platinum plugs.

I also replaced the master electrical switch with a new one. That cured the problem of engine stalling and then higher idle when the brake pedal was depressed.

The car is missing the O2 sensors. Wouldn't that cause rich condition? Should I be looking at the injectors (leaking) instead?

Suggestions?

Thanks for your assistance.

Rick

 

[Methodical]

Is the car running in limp mode now without the O2s? It seems that the car would be running really bad without o2s to tell the computer whether it needs more or less fuel. You may want to post in the tune section to get a legit answer on this. Oh are the bungs cap on the exhaust or just open?

 

[Black95GTS]

I am working on a 94 Mustang that is running in the Camaro-Mustang Challenge (NASA.) The car has been running for a couple years but recently started having problems with a high-rpm miss. I just saw the car for the first time yesterday so all the history is hearsay.

The plugs were very black and some had fuel fouling when I pulled them out. The plugs being used were 4 prong platinums. I replaced them with new Bosch Copper (on hand and free) as I have heard that some ignitions can't handle the increased gap and higher resistance of platinum plugs.

I also replaced the master electrical switch with a new one. That cured the problem of engine stalling and then higher idle when the brake pedal was depressed.

The car is missing the O2 sensors. Wouldn't that cause rich condition? Should I be looking at the injectors (leaking) instead?

Suggestions?

Thanks for your assistance.

Rick

How is it tuned? You can force a car to only read from the maf. For example, if you go wide open throttle on the stock tune, you are only using your MAF to determine A/F ratio. There might be some seriously funky tuning going on.

Adam

 

[HISSIN50]

Adam, I thought that the Sn95 processors indeed use lambda input at WOT.

I only know how a fox will do with no O2's, so Im gonna shut up now.

 

[rad23racer@hotm]

Well, time for egg on the face and crow eating at the same meal...

O2 sensors present. The plug I thought was O2 was actually EGR.

Pulled codes, all related to missing EGR system. EGR is plugged in manifold.

Will be checking plugs in a few minutes as I had to change classrooms.

Anything typical? Coil, injectors, etc? When we pulled the plugs, a couple were gasoline fouled. I think at this point that was due to the cylinder not firing. When we pulled them, I attributed the no-fire due to the platinum plugs.

Thanks for the ideas...keep them coming.

Rick

 

[Black95GTS]

Adam, I thought that the Sn95 processors indeed use lambda input at WOT.

I only know how a fox will do with no O2's, so Im gonna shut up now.

Hmmmm that is interesting. I'm pretty sure that the only sensor giving input at WOT is the MAF... BUT, its definately possible that it takes into account previously stored lambda values.

So what would happen if there were no lambda values to be used if you were tuning with just a "WOT" status? Would that be introducing a zero in for a variable? That would definately cause some pretty rough things to occur.

Now I'm confused.

GRADDYYYY!!!!

Adam

 

[Swarzkopf]

I'm 90% positive that the car only relies on the MAF at WOT. Still, no 02 sensors would cause a massively rich condition at idle and during anything but WOT.

Anyway, as he explained, that's not the case. This is:

Well, time for egg on the face and crow eating at the same meal...

O2 sensors present. The plug I thought was O2 was actually EGR.

Pulled codes, all related to missing EGR system. EGR is plugged in manifold.

That's a problem. Deleting the EGR is fine IF you tune it out, even it's with a simple EGR harness plug that fools the computer into not throwing a code.

The EGR code can cause all sorts of tune issues. I believe that it generally causes a lean condition, but I wouldn't suprised if it could cause a rich condition as well.

Either tune out the EGR in the car's EEC or buy a cheap EGR harness plug on Ebay (like $20).

 

[SeventyMach1]

First, I say FIX THE EGR. It's not "tuned out" of the computer because it's throwing EGR related codes. (either tune it "out" .... or replace the EGR)


Also, get some Motorcraft or Autolite plugs. Then go from there.

 

[Swarzkopf]

First, I say FIX THE EGR. It's not "tuned out" of the computer because it's throwing EGR related codes. (either tune it "out" .... or replace the EGR)

I was saying the same thing...he can either tune it out using a Tweecer or other means of modifying the EEC program or he could buy an EGR delete wiring harness plug which effective does the same thing.

 

[Don 95Vert]

Without a chip to fix the adaptive fuel table, if the car is running at idle and part throttle really lean for extended periods of time, the EEC will take the correction factor it is applying down low and also apply it up top (WOT) to the base fuel table. The EEC mainly uses the MAF at WOT, but indirectly uses the 02 sensors at WOT in this way.