A/F ratio going out of control Issues

[supraguy31]

Ok all, Ive talked about this a few times in Earlier threads and I dont want to bring a Old thread back to life so Im just going to shoot you all a problem and I wanna know if Im looking in the right or wrong Direction.

Since I went from a ct26 Based setup to a V-Band flange setup I have had nothing but trouble with my Wideband A/F ratios. Mornings Im Idling at 15.7and by the time I get to work which is only 10 Miles or so, My A/F ratio at Idle is 13.1 to 13.5, Under load or normal driving condition when I first start off in the morning its 14.4 to 14.7 but starts to drop in the rich area the farther I drive. this afternoon when I drove home It wouldnt get out of the 11.0 range and that is just normal cruising.

Everything is set of my VPC to 0 (12 Oclock) and everything on my SAFC is at 0 across the RPM band. Only way I can get it to go back to 14.7 when driving is to put the Low throttle settings on -33% at the 2000 and 3000 RPM range and turn the VPC Idle bottom to -14 on the lean side.

The only thing that I can remember changing when I went to this type setup is from a Factory O2 Sensor to a Aftermarket Ford Mustang 3 Wire sensor. Its the one that people on here recommended. Once I did that is when Ive started having these problem and nothing I have done has changed anything. Could it be the Aftermarket O2 sensor causing this. If so, Is there another type O2 sensor that I can purchase other than this one. Ive bought another one and another Wideband sensor and no Change when they were installed.

Please someone let me know if I might be on to something here. Frustration is starting to really set in to the point that I want to just sell and get out of Supras all together.

Thank you for your time and for reading this.
Robert

 

[TurboStreetCar]

Since its the only thing you changed i would bet thats it. Is it heated? IIRC the stock one is.

What are your other mods?

 

[suprahooked]

What size injectors are you running and do you have aflow sheet for them? What is your fuel pressure?

 

[jetjock]

PM sent...

 

[SPD TRP]

Ok all, Ive talked about this a few times in Earlier threads and I dont want to bring a Old thread back to life so Im just going to shoot you all a problem and I wanna know if Im looking in the right or wrong Direction.

Since I went from a ct26 Based setup to a V-Band flange setup I have had nothing but trouble with my Wideband A/F ratios. Mornings Im Idling at 15.7and by the time I get to work which is only 10 Miles or so, My A/F ratio at Idle is 13.1 to 13.5, Under load or normal driving condition when I first start off in the morning its 14.4 to 14.7 but starts to drop in the rich area the farther I drive. this afternoon when I drove home It wouldnt get out of the 11.0 range and that is just normal cruising.

Everything is set of my VPC to 0 (12 Oclock) and everything on my SAFC is at 0 across the RPM band. Only way I can get it to go back to 14.7 when driving is to put the Low throttle settings on -33% at the 2000 and 3000 RPM range and turn the VPC Idle bottom to -14 on the lean side.

The only thing that I can remember changing when I went to this type setup is from a Factory O2 Sensor to a Aftermarket Ford Mustang 3 Wire sensor. Its the one that people on here recommended. Once I did that is when Ive started having these problem and nothing I have done has changed anything. Could it be the Aftermarket O2 sensor causing this. If so, Is there another type O2 sensor that I can purchase other than this one. Ive bought another one and another Wideband sensor and no Change when they were installed.

Please someone let me know if I might be on to something here. Frustration is starting to really set in to the point that I want to just sell and get out of Supras all together.

Thank you for your time and for reading this.
Robert

I was once told that you should replace the oem o2 sensor with another oem, something about its design or something, can't really remember.

I know that when I was running the 7m and when I unplugged the o2 my afr's would be in the high 12's to low 13's, plug it in and back to 14.7.

I would get an oem one, I know they are kinda pricey, but call jeff watson at champoin toyota, you will get the best deal there.

Wayne

 

[supraguy31]

Only Problem with that is Im running a Aftermarket Exhaust System 3 1/2" and I havent found anyone or anywhere that sells the OEM style o2 Sensor in a Screw in Bung. The one I have right now is a 3 wire Heated as per the members on the forum stated. 2 white wires and a Black wire.

As for Injectors, Im running Stock 440 and with 550 that I was running it was doing the same thing and Im running a MKIV fuel Pump set to Stock Fuel Pressure. Getting ready to put the 550s back in since it didnt change anything with the 440s and Yes I have both the 440 and 550 VPC Chips

 

[supraguy31]

I know that when I was running the 7m and when I unplugged the o2 my afr's would be in the high 12's to low 13's, plug it in and back to 14.7.Wayne

Update on a Specific Remark that you said............

Well, I went outside last night, Popped the hood, Unplugged the NB O2 Sensor and started the car and let it engine was up completely. My WB O2 sensor reading went to 12.0 to 12.1 and didnt move a inch. I said ok and I went up and Plugged the NB back in and the WB A/F ratio stayed Exactly at 12.0 to 12.1

Well, I disconnected it again and I got into the car, Reved the engine up to 3000 to 4000 rpms and I didnt get any type of CEL saying the the O2 sensor was bad or Disconnected or anything. It was just like the motor wasnt even tracking the NB or something.

Robert

 

[TurboStreetCar]

Put a volt meter from VF in the check diagnostic box to ground and look at the voltage.

Thats fuel trim, if the TCCS is changing the fuel trim youll see it there. if its 0v consistently your in open loop.

 

[Supraholics]

Put a volt meter from VF in the check diagnostic box to ground and look at the voltage.

Thats fuel trim, if the TCCS is changing the fuel trim youll see it there. if its 0v consistently your in open loop.

IIRC you should be in .4 or .5v correct?

 

[jetjock]

It should be in one of the midrange steps under steady state conditions with around 2.5 volts or so being optimal. That said in this case looking at the learned value is less useful than looking at the emulated feedback signal, which requires looking at Vf with the diag block jumpered and the engine off idle.

A couple of good suggestions were made here. One was to unplug the NB sensor to see if the ECU is capable of controlling mixture in the default range while in open loop. It appears to be doing so and that proves a lot of things are working correctly. That leaves the implication of an inop or shifted fuel loop as the problem. The next step would be to verify NB operation.

That said it's important to remember the EFI system is usually not at fault. It gets blamed for all sorts of things when the real problem is typically something more basic ie; timing, pirate air, ignition, etc. In this case however me thinks the postings are on the right track. An upstream of the sensor exhaust leak might be at fault too.

 

[supraguy31]

VF Signal with the jumper off the Diag box shows that im getting a consist .04 to .05v as its bouncing between them regardless of weather the O2 sensor is connected or Disconnected or engine is reved to 2500rpms.

Jump the T and E1 connector and then check the VF Signal and as soon as I touched a ground point it went straight to 5.02, Rev the engine to 2500rmps and it Dropped straight to .4 to .5v, Disconnect the O2 sensor and check again and im still getting the 5.02 reading and drops down to .4 to .5v when Im at 2500rmps.

A/F Ratio at Idle right now with the O2 connector or Disconnected is 12.5 to 12.7

Am I on to something with all you guys help.

 

[TurboStreetCar]

Well if the fuel trim is saying the mixture is good via 2.5 volt signal it would show the TCCS is receiving an erroneous air fuel ratio reading.

If the sensor is saying 13:1 is 14:7 the TCCS will adjust the mixture untill it is 13:1 instead of 14.7:1 and show neutral fuel trim.

Without jumping anything and measuring voltage between Vf and ground and getting a reading below 1 volt means the TCCS is pulling fuel as much as possible.

Your running rich and the computer knows it, though it cant pull enough fuel to correct the problem.

You said if you pull 33% in the low range it goes back to normal, do so and check the VF voltage again to see if it changes.

You also said your running a MK4 pump, did you eliminate the J tube restriction?

 

[supraguy31]

Yes, I eliminated the Jtube. Im actually running a Aeromotive FPR.

Ok so I decided to pull everything out of the car and bring it back to completely stock except the FPR and Pump. Pulled all the VPC stuff out of it, Connected the AFM back into the car and all that.

turned the Key and it started really bad but I gave it a Little fuel and it Idled up to about 16.4 on the Wideband. Use the throttle and hold it at 2500 rpms and it dropped to 13.4 or so but didnt come back to 14.7, I shut the car off, Immediately started it back up and what do you know, My WB a/f readings at Idle went to 13.4 and If I hold it at 2500 rpms It dropped to 11.5 or so. Everything is back to Stock Configuration and I dont have any Fuel leaks. I will check the VF Signal and let you know what its saying now.

VF Is showing a Consistant 2.21 at Idle and at 2500 rpms but the WB A/F ratio is still showing Pig rich when you Give it gas. Idle is at 700rpms and Idle A/F is Mid 13s, Finally through a Code 24 so Im checking that out now.

 

[SPD TRP]

You said you were running an aeromotive fpr, what is the baseline fuel pressure (no vacuum), and the fuel pressure with vacuum is applied. If I remember correctly, it should be 40 psi and 30 psi respectively.

Wayne

 

[supraguy31]

Ok, Here is something that I noticed this morning and totally forgot to put it on here.

When I first start the car up and let it completely warm up and then check the VF Readings im almost getting nothing at all ie .04 to .05 on my Miltimeter and the A/F ratio is reading where it should be. Now as soon as I shut the car off and start it back up and let it setting the VF setting start reading 2.25 and that is when the A/F ratio Drops real rich.

Basically its like its not reading when its cold and after everything warms up and I basically shut everything down and restart, Everything starts to read like it should. Im going to see what I can do about getting some type of Factory Bung welded into my Exhaust so I can use the Stock O2 Sensor instread of a Aftermarket one. I just bought another one, Installed it and Absolutely no change.

 

[supraguy31]

You said if you pull 33% in the low range it goes back to normal, do so and check the VF voltage again to see if it changes.

Once the VF Started to read 2.24 after I restarted the car, I pulled -22% on 1000 and -18% on 2000 rpm Band and the VF signal didnt budge at all.

Robert

 

[jetjock]

Warm the engine up. Measure Vf with the diag *jumper in* and the engine at 2500 rpm. You said it's 5 volts right? Pull the brake booster line off. What does Vf do then?

Or measure OX in the diag block (use millivolt scale on the meter) and do the same thing. Does it drive the sensor lean?

Edit: got your PM. No need to reply.

 

[TurboStreetCar]

so the vf was 2.24 and it was rich, you pulled fuel to get to ~14.7, and the the VF stayed the same as it was before changing the mixture? Seems its the 02 sensor. if the a/f changed and the TCCS didnt do anything to react, it didn't see the change in a/f.

The 02 sensor uses voltage to show oxygen content in the exhaust pipe, and the TCCS uses that to find the right mixture. the TCCS richens the mixture until the 02 voltage gets to a certain point (most likely somewhere around 14.9-15 to 1). when that point is reached then the TCCS leans the mixture until the 02 sensor voltage gets to another certain point (most likely around 14.2-14.5 to 1). it does this very quickly witch makes the 02 voltage sweep and that method nets the correct ~14.7:1 air fuel ratio.

How much it has to richen and lean is the fuel trim. The mixture control is directly based off of this input unless it is deemed wrong by the TCCS. It will throw a code when it deems that input wrong. If the mixture changes, and the fuel trim stays the same, it didn't see the change in air fuel ratio.

It might be slightly more complicated then this, but thats basically how it works.

You can use this to test the sensor, but i would go back to the stocker. Even if you have to weld the flange to the down pipe.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=119

 

[jetjock]

^ It's a bit more complicated than that but close enough.

The stock sensor is indeed special in some respects but most any zirconium sensor will work well enough to avoid what he's seeing. However if it can't be driven it lean and rich around the stoichiometric point the engine will never enter fuel control.

Sometimes the sensor vent gets plugged and it can't sample ambient O2. On many sensors this vent is through the wiring and easily gunked up. Since he's bought a new one I doubt that's his problem though. Anyway, he needs to test it either on or off the car followed by a check of the wiring. Frankly I'm amazed such a simple problem could take on such epic proportions...

 

[supraguy31]

First of all I want to say thank you to JetJock for all His help the past 2 days. We probably email on another over 20 times talking about this Situation and I think we finally got it figured out to a Point.

We found that on my engine wiring harness one of the O2 Sensor wires were broken to the point that there was one tiny Strand of wire holding it together. Cut, Splice and Solder it back together and my A/F ratio jumped back up to normal range. So this is where we are at this Point. He told me to take it out for a drive and Observe the A/F readings.

I started it up this morning and let it Idle (15.5 to 16.2) so I took it out on the road and got up to cruising range (14.4 to 15.2) and it ran like this for about 4 or 5 miles, Then all of a sudden or out of the blue the A/F ratio just Dropped to 10.5 to 11.0 for about a minute and then started to climb back up until it got back into the 15.5 to 16.2 Range. Now why would it drop so quickly and then Adjust itself back correctly?

Ive heard that these 89 Mustang 5.0 sensors are great but the Signal is alot slower or Doesnt register as fast as the Original toyota Sensor does?

Robert