7mgte going extremely lean only at WOT. I believe its a wiring / signal issue. Help

[queenskid926]

My 87 supra is running extremely lean only at wide open throttle.
This randomly started and I believe its an issue with the wire harness (ecu or sensor is not gettin, recieving the proper signal) but first here are the mods and steps that I already took to try and fix the issue.

Mods That Would have any effect
Aem wideband, Stock turbo 12lbs, Stock injectors, Stock Afm, Aeromotive fpr, MKiv TT Denso fuel pump. Safc 2. Egr Delete, Jdm Ecu. J tube bypass

Car was running fine, no issues at all, afr was in check with the wideband, 11-11.3 under wide open throttle and randomly it would spike up to 13 (wtf). i then purchased a Aeromotive fpr, egr delete and jdm ecu and installed the above item, No change at all.

Continue to test and at idle, and cruising the afr again was in spec but only would run lean at wide open throttle. it would go to rich then spike and stay in the mid to high 12-13 afr .

Things that i did to try and correct the issue:
I removed the safc2 and have the harness wired back to stock.
Raise fpr on the aeromotive to 50psi base, (Didnt change anything still really lean under wot like ecu isnt telling the injectors to stay open for the proper duration)
Change fuel pump.
Change afm
change throttle body.
Change ecu.
Check for codes, (No codes stored)
Check to see if the tps is in spec ( it is)
Measured voltage at ecu through the tsrm. Everything is in spec Depending on which section in the tsrm i look at.
according to this link http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=51.

with the throttle body wide open between vta - e2 im getting 3.4v which shows that its in spec with t above link but on this section it says the range should be between 4v and 5 v this link here http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=122

Which one should I go buy?

Also I've had wiring issue with this harness before, code 11 no Batt signal and I fix that by running a wire straight from the battery with a 15amp fuse in between straight back to the pin Batt on the ecu and that fixed that issue.

If this is a result of a short in the harness, I will do the same, run the wire from the affected sensor straight back to where it plugs into the ecu.

I was thinking maybe it has something to do in the tps, afm, ecu water temp, or o2 sensor, circuit? Doesnt it use those sensors to control the air fuel ratio? Any way i can check?

Again no codes are being throwing and also there is no vacuum leak between the afm and turbo.


Thank your for looking and please any advice would help.

Thanks Ron

 

[queenskid926]

also i swapped the wideband with a friend to verify that its not the wideband and there is zero exhaust leaks before the wideband

 

[Nick M]

My 87 supra is running extremely lean only at wide open throttle.

The TPS is an important correction factor. You need to actually check it with a scope. That might not be the problem, but if it only happens when your foot is on the floor, and not under other very heavy loads, I would look at it.

Change fuel pump.
Change afm
change throttle body.
Change ecu.
Check for codes, (No codes stored)
Check to see if the tps is in spec ( it is)

That sounds like an expensive check, considering it wasn't actually checked. You do know that 12 psi is in fuel cut range with the stock ECU.

 

[queenskid926]

The TPS is an important correction factor. You need to actually check it with a scope. That might not be the problem, but if it only happens when your foot is on the floor, and not under other very heavy loads, I would look at it.


That sounds like an expensive check, considering it wasn't actually checked. You do know that 12 psi is in fuel cut range with the stock ECU.

thanks most of the parts i change were upgrades stock fuel pump to the tt denso one, stock fuel pressure regulator to the aeromotive one etc etc
i swap throttle bodies with another and it had no effect

i tried turnin the boost back to stock (turn the manual boost controller all the way back) no difference stil lean under wot

 

[DeadlyWrenches]

How about checking the fuel pump relay and resistor? http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=114

You mentioned checking the water temp sensor and oxygen sensor, did you actually check them?

Water temp sensor http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=113

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

 

[Nick M]

i tried turnin the boost back to stock (turn the manual boost controller all the way back) no difference stil lean under wot

That won't matter if you have an intake leak. Did you check codes? You have to drive the car and get the symptom to happen before checking.

 

[3p141592654]

I don't see anything about whether you still have the MK3 fuel pump speed control circuit in place. Since you are using the Denso 1020 pump, you cannot use the MK3 fuel pump resistor setup as the resistor is too large and will choke the pump off. I would expect you would see the car go lean until the ECU switches over to full speed, not quite like your symptoms, but you might be seeing the effect of going lean before switchover, especially if your TPS is worn.

Either do the 12V mod, or use two MK3 resistors in parallel (my preferred solution).

 

[kikdurazz]

You said you raised fuel pressure up to 50psi base and it's still going lean. Are you sure you have the vacuum lines setup correctly to the afpr. If they're not then fuel pressure won't rise with boost and just stay static causing you to go lean. That would be the simpliest explaination.
I had the wrong vac line going to regulator and we couldn't figure out the lean issue until we started running into boost on the dyno and watching the FP too see it rose which it didn't.
placed the line correctly problem solved and base pressure used again and fuel pressure would match boost 1:1.

 

[bluepearl]

Did you perform a fuel pump volume test? Also, do you have a fuel pressure gauge in the cabin to monitor pressure when this happens?

 

[queenskid926]

First i would like to say thank you all for your response.

How about checking the fuel pump relay and resistor? http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=114

I did the 12volt fuel pump mod. I have a 10guage wire going straight to a relay that i have wired in, then going to the fuel pump. The fuel pump sees 12volts all the time when the ignition is on.

Also I just changed the ecu water temp and o2 sensor from another working car. I didnt check the circuit. I will look at your links right now after I finish responding.

I don't see anything about whether you still have the MK3 fuel pump speed control circuit in place. Since you are using the Denso 1020 pump, you cannot use the MK3 fuel pump resistor setup as the resistor is too large and will choke the pump off. I would expect you would see the car go lean until the ECU switches over to full speed, not quite like your symptoms, but you might be seeing the effect of going lean before switchover, especially if your TPS is worn.

Either do the 12V mod, or use two MK3 resistors in parallel (my preferred solution).

Did the 12volt mod already 3p141592654;1616569. How i have it wired setup is above, i did the 12 volt with the stock fuel pump about 6 months before this issue started happening. Then i changed to the TT Denso fuel pump and the issue remained, But hey, I was going to upgraded it anyways...

Did you perform a fuel pump volume test? Also, do you have a fuel pressure gauge in the cabin to monitor pressure when this happens?

No i have a fuel pressure guage hooked up to the afpr. I will look to see if i can find an adapter just so i can watch the guage on a pull. I will look into that.

You said you raised fuel pressure up to 50psi base and it's still going lean. Are you sure you have the vacuum lines setup correctly to the afpr. If they're not then fuel pressure won't rise with boost and just stay static causing you to go lean. That would be the simpliest explaination.
I had the wrong vac line going to regulator and we couldn't figure out the lean issue until we started running into boost on the dyno and watching the FP too see it rose which it didn't.
placed the line correctly problem solved and base pressure used again and fuel pressure would match boost 1:1.

I have it hook up with the proper vacuum diagram from the vsv fp up switch. Also i changed the vsv with another one and test it out per tsrm and even hooked up the vaccum line to one running off the back of the intake manifold so i know that it sees boost and still no change at all.

---------- Post added at 07:33 PM ---------- Previous post was at 07:30 PM ----------

That won't matter if you have an intake leak. Did you check codes? You have to drive the car and get the symptom to happen before checking.

Yes i reset the ecu, clear all codes, no code being shown, drove the car to recreate the problem, did 3 or 4 short pulls cause its reading 13afr at 8lbs, (im still on stock hg, dont want to blow it up) and no codes at all where stored

 

[Nick M]

The fuel pump sees 12volts all the time when the ignition is on.

Do you know what throwing fuel on the fire is?

Yes i reset the ecu, clear all codes, no code being shown, drove the car to recreate the problem, did 3 or 4 short pulls cause its reading 13afr at 8lbs, (im still on stock hg, dont want to blow it up) and no codes at all where stored

Don't erase the codes. I would check with a 4 or 5 gas analyzer over a wideband. Not that a wideband is bad, it just doesn't give a lot of information.

 

[queenskid926]

Do you know what throwing fuel on the fire is?



Don't erase the codes. I would check with a 4 or 5 gas analyzer over a wideband. Not that a wideband is bad, it just doesn't give a lot of information.

They were zero codes to begin with. When the issue first started happening, I check for codes instantly, and there was none. I continued to do so, over and over, after swapping parts just to see if it would tell me something. i hit fuel cut once when i swaped in another afm and thats the only code that i had to reset. I probably check for codes everyday after a drive and nothing, No codes are being thrown at all.

 

[3p141592654]

I think you need to monitor fuel pressure during a run. Clogged filter is a possibility.

 

[queenskid926]

I think you need to monitor fuel pressure during a run. Clogged filter is a possibility.

ok i will purchase a electronic fuel pressure gauge and install the sensor where the one is now on the aeromotive fpr and run the wiring and gauge back to the cabin to see wats happening.

If that is an issue, than, i will replace the whole fuel system -8 or -10an from the tank to the engine, (which i planed to do anyways, just later down the rd)

It just finish raining over here, Im off to go check the o2 and water temp sensor per tsrm from the links.

Thanks

 

[92TealSupra]

I would first go through your harness where the SAFC2 was wired in. My rule is, if there was not a problem before you did something, and you do a mod on your car and there is a problem, you know where to start. ensure that the wires you put back together are properly soddered together. A lot of people do it incorrectly causing wrong voltage, or no voltage to the area needed.

Are all connectors on your harness in good working order? Injectors are not clogged at all? Were they test at all? Also a fuel filter could get clogged, but most of time it is not that. Knowing fuel pressure the entire time will help. If there is a drop for some reason you will know where to start looking.

Check all ground to make sure your getting the proper voltage on the harness. A guy stopped over and had a Supra and his starter was getting around 8.4 volts. I hooked up a few more grounds properly and it ended up with 13.2 V, so things like this can affect a lot.

Keep us updated, I would like to see where this is going, and what it is. Good luck, and we'll all do our best to help you through this.

 

[queenskid926]

I would first go through your harness where the SAFC2 was wired in. My rule is, if there was not a problem before you did something, and you do a mod on your car and there is a problem, you know where to start. ensure that the wires you put back together are properly soddered together. A lot of people do it incorrectly causing wrong voltage, or no voltage to the area needed.

Check all ground to make sure your getting the proper voltage on the harness. A guy stopped over and had a Supra and his starter was getting around 8.4 volts. I hooked up a few more grounds properly and it ended up with 13.2 V, so things like this can affect a lot.

Keep us updated, I would like to see where this is going, and what it is. Good luck, and we'll all do our best to help you through this.

When the problem first happen, I turn the boost back down to stock and then reset all of the adjustments that where made on the safc. I had the safc on the car for months now without an issue. I then took out the safc, and wired everything back to stock, No changes.

Grounds on the harness I believe are good, When checking the terminals of the Ecu, +b and +b1 The voltages was where they should be.

I check the 02 sensor per the tsrm last nite .
Car fully warm.(Had to drive it about 20 miles home)
Engine at 2500rpm, connected t and e1, conected volt metter to e1 and vf and the voltage that i first read was .8 and it would fluctuate to 1 and back.
However it wasnt fluctuating the 8 times in 10 seconds, so i retest again and it was the same amount of voltage and wasnt fluctuating enough times.
Did the test one more time and out of no where the voltage started going crazy ranging from 1.2 -4.2 constantly fluctuating jumping all over the place all the time.
Drove the car right after, no changes, still the same problem.

Looks like I'm having a short or issue in my 02 sensor circuit?
Please clarify how the 02 sensor is ran. You have one black 12v wire for the heater wire that runs to the 02 when the ign is on. The other Black wire is a ground, and the Blue signal wire is ran to the ecu. Shouldnt there be some amount of voltage on that signal wire to tell the ecu whats going on? I am reading the 12v heater wire but im not getting any voltage at all on the blue signal wire while the car is running.

 

[queenskid926]

Just check for voltage between signals OX and E2 at the connector side of the ecu while its still plug in and car is running. No voltage at all, Shouldnt there be something coming from the 02 Sensor to the ecu to let it know whats going on?
Here is a ecu pinout for my yr
http://img.photobucket.com/albums/v327/prettiboi717/Rebuild in Progress/ECU-pinout-87.gif

Im trying to research how is the oxygen sensor wired up? the pinout of the connecter and does it run only back towards the ecu.

 

[queenskid926]

going to go to homedepot and purchase some fitings and a high pressure rubber hose to extend the guage into the cabin temporaily as i do a few pulls, will update with the results

 

[queenskid926]

It was the Fuel Pressure, Hook up a way to extend the guage from the FPR into the cabin and did a pull, fuel pressure would try and spike up then drop. That was with the Vacuum line hook up from the fuel pressure up vsv. I changed it with one i have going to my boost guage so i know that it sees boost and again it stayed the same pressure and then slowly drop 2-3psi.

Going to drop my tank 2moro and install screw clamps on the fuel pump hose inside the tank instead of the factory squeeze clips and see if its changes anything.

Thanks guys

 

[Nick M]

The oxygen sensor is not input to the ECU at wide open thorttle.