4th gen 3sgte running really rich

[UtahSleeper]

Located in SLC, UT.

So, where to start........I have an 88 Alltrac with a 4th gen 3sgte. Runs, starts and drives, but is running pig rich. I can share the emission numbers if wanted.

https://www.youtube.com/watch?v=_lP7lxU-PYU

So, I made a short video of what my ecu is showing while idling. No audio, but figure the gauges tell the story. I did idle and 2500 rpm hold.

I have replaced o2 sensor, MAP, TPS, and plugs. Not sure where to look next. I have also added a fuel pressure gauge to verify pressure was fine. At idle it was around 35 psi.

The fact it shows a high load makes me wonder if that is tied to the issue.

What makes this weird for me is these things:
Torque seems to show all sensors and valid data. With the O2 showing it running rich, I would think the ECU would lean it out.
Torque shows a temperature, so it doesn't seem like a bad temp sensor.

Just looking for any guidance on what to try next. I am thinking of replacing the coolant sensor next, but am open to suggestions.

Thanks for any feed back.

[sergei]

If the oxygen sensor has been replaced, and ECU reset (so it relearns new long term fuel trim), it all points to wrong injectors or leaky injectors, as ECU is desperately trying to compensate to the max (-20% Fuel Trim).

Does it hold fuel pressure when off?

Assuming by 4th gen (and by info you can get out from torque app) it is motor out of caldina GTT/GT Four then the injectors should be sky blue.

[BlakeNZ]

that 35 psi base fuel pressure is not too high at idle. IMHO.

[UtahSleeper]

If the oxygen sensor has been replaced, and ECU reset (so it relearns new long term fuel trim), it all points to wrong injectors or leaky injectors, as ECU is desperately trying to compensate to the max (-20% Fuel Trim).

Does it hold fuel pressure when off?

Assuming by 4th gen (and by info you can get out from torque app) it is motor out of caldina GTT/GT Four then the injectors should be sky blue.

Thanks for the info on the injectors. I will verify the color of them. The models you listed is what I am under the impression it came out of.

I will check the fuel pressure when the engine is off. I think it turns the FP off, but I will verify.

[UtahSleeper]

If the oxygen sensor has been replaced, and ECU reset (so it relearns new long term fuel trim), it all points to wrong injectors or leaky injectors, as ECU is desperately trying to compensate to the max (-20% Fuel Trim).

Does it hold fuel pressure when off?

Assuming by 4th gen (and by info you can get out from torque app) it is motor out of caldina GTT/GT Four then the injectors should be sky blue.

Well, the injectors are the right color, so I am going try and get the injectors cleaned. Going the easier route first and do a cleaning on the car. If it improves things then I will probably buy a spare set and get those professionally cleaned.

[Akane]

Without wideband output, the data is not useful enough for you to troubleshoot your issues.
Suggest you get a wideband before you start adjusting things that don't need to be adjusted.

[sergei]

If the oxygen sensor has been replaced, and ECU reset (so it relearns new long term fuel trim), it all points to wrong injectors or leaky injectors, as ECU is desperately trying to compensate to the max (-20% Fuel Trim).

Does it hold fuel pressure when off?

Assuming by 4th gen (and by info you can get out from torque app) it is motor out of caldina GTT/GT Four then the injectors should be sky blue.

Well, the injectors are the right color, so I am going try and get the injectors cleaned. Going the easier route first and do a cleaning on the car. If it improves things then I will probably buy a spare set and get those professionally cleaned.

If you have one leaky injector then you can tell by looking at sparkplugs, the faulty injector will show up as black centre on spark plug (ignore the blackness on outer).


It might also be wet.

[UtahSleeper]

So, new recording. Tell me if these are helpful. No audio, but I did a couple 2nd and 3rd gear pulls to see what the ecu was doing under actual load. The one thing I noticed is the O2 seems to read what is expected when under boost.

https://www.youtube.com/watch?v=KschOJxjFRk

I am planning to replace the coolant temp sensor as recommended, but I am really wondering if it is needed since the ECU seems to show the correct temp. Should I even worry about it or could something else be going on?

Also, why can't a narrow band be used for troubleshooting? And are the O2 sensors of today really that bad? I ask cause it seems to be very useful information given through the app and the wideband in my corolla doesn't seem to give much different information output. I know older o2 sensors were not very good past stoic, but not sure what is so bad with newer ones. Also, not really anything I can adjust lol. Just trying to find what is causing it to read and run pig rich and replace it since something seems obviously broken. What could a wideband offer that is not being given by the stock o2?

I will check my plugs. When I replaced them a 100 miles or so ago they all seemed reasonable wear, just old/worn. Closer to the normal image, just a little darker.

[UtahSleeper]

And here is what the plugs looked like when I replaced them. The car was running rich and it failed the emissions test with these. Haven't retested the car cause I can still smell the exhaust.





And here are the emissions.

[RS13]

You replaced those plugs? Those plugs in the pic are as old as the hills, note the staining on the porcelain which indicates compression leakage.. they've seen better days.

I've fixed half a dozen badly-running 3S engines now by simply replacing the CTS.. they're a known weak spot in the 3S engines. The last (Caldina) was running so rich it was a pig to start and wouldn't idle, swapped in a new CTS (they're around $30 in NZ) and problem gone. Always the first thing I replace now.

[UtahSleeper]

You replaced those plugs? Those plugs in the pic are as old as the hills, note the staining on the porcelain which indicates compression leakage.. they've seen better days.

I've fixed half a dozen badly-running 3S engines now by simply replacing the CTS.. they're a known weak spot in the 3S engines. The last (Caldina) was running so rich it was a pig to start and wouldn't idle, swapped in a new CTS (they're around $30 in NZ) and problem gone. Always the first thing I replace now.

K, I will replace it. Just was more curious as to what to take from the ECU seeing a proper temperature. Or is there more going on in a temp sensor then just the signal being sent for temp?

[sergei]

You replaced those plugs? Those plugs in the pic are as old as the hills, note the staining on the porcelain which indicates compression leakage.. they've seen better days.

I've fixed half a dozen badly-running 3S engines now by simply replacing the CTS.. they're a known weak spot in the 3S engines. The last (Caldina) was running so rich it was a pig to start and wouldn't idle, swapped in a new CTS (they're around $30 in NZ) and problem gone. Always the first thing I replace now.

K, I will replace it. Just was more curious as to what to take from the ECU seeing a proper temperature. Or is there more going on in a temp sensor then just the signal being sent for temp?

how do you correlate temperatures? The ~80'C on the gauge (180'F) is a bit on low side under load (it should be around 90'C or so, unless it is freezing outside).
Looking at your second video I see FT spot on under light load as well as O2 voltage fluctuation correctly, so there it is not running rich.
I am leaning toward bad CTS....

The sensor is just a thermistor (changes resistance depending on the temperature).

[UtahSleeper]

You replaced those plugs? Those plugs in the pic are as old as the hills, note the staining on the porcelain which indicates compression leakage.. they've seen better days.

I've fixed half a dozen badly-running 3S engines now by simply replacing the CTS.. they're a known weak spot in the 3S engines. The last (Caldina) was running so rich it was a pig to start and wouldn't idle, swapped in a new CTS (they're around $30 in NZ) and problem gone. Always the first thing I replace now.

K, I will replace it. Just was more curious as to what to take from the ECU seeing a proper temperature. Or is there more going on in a temp sensor then just the signal being sent for temp?

how do you correlate temperatures? The ~80'C on the gauge (180'F) is a bit on low side under load (it should be around 90'C or so, unless it is freezing outside).
Looking at your second video I see FT spot on under light load as well as O2 voltage fluctuation correctly, so there it is not running rich.
I am leaning toward bad CTS....

The sensor is just a thermistor (changes resistance depending on the temperature).

My temperature is a little low mostly cause I have a performance radiator and a fan that doesn't turn off lol. PO removed the AC system and apparently if you remove the AC pressure sensor on these alltracs it will keep all fans on, so I'm told. Plus, we were in the 60's yesterday so that didn't help warm it up. I can tell when the thermostat opens up though when idling.

Again, thanks everyone for the assistance. I am just trying to get a better understanding of what I am fighting Already ordered the cts, now just have to wait.

[RS13]

Ah k. That might be your issue right there.. a big radiator and constant fan means the car will take a long time to heat up, or rarely get to correct operating temperature so the ECU may be adding fuel to compensate. Constant fans on a road car aren't as beneficial as people seem to think they are and long-term can actually end up damaging the engine.. Sergei will probably know how to bridge the AC switch to stop the constant fan, I'd still change the CTS to rule it out though.

[GDII]

If it's anything like an MR2 you will just need to find the AC pressure switch and bridge it. This will turn off your fans and they should only run when required.
As RS13 said, cold coolant will not let the car run properly making the ECU throw in more fuel because it thinks it's still warming up.

EDIT: If the wiring for the AC is still there it should be somewhere near where the AC lines run into the firewall.
See Image 2 on the right hand side. http://jp-carparts.com/toyota/partlist. ... 1&fig=8718
Part numbers 88645 (no.1 and no.2)
It's the JDM diagram so your car might have it on the other side of the car, either way this should help.

[sergei]

It will be most likely 4 wire plug like so:



From what I remember the two white-black (wire colour-stripe colour) are grounds, and other two are signal.
The plug is oval or elongated circle. The wires that are needed to be shorted are further from each other.



basically if you short pin on the left with pin on the right from above diagram, it should turn off radiator fan.
From memory it is white-black wire shorted to green-something wire.

I could be wrong regarding which wire to ground (the white-black wires are 100% ground).
Regardless, you could try to ground either wire that is not white-black and see which turns off your fan (providing that the fan thermo-switch is connected).

[UtahSleeper]

So, update and recap. Still looking for suggestions.

I have replaced the coolant temp sensor(at water neck), MAP and TPS. No changes in readings interpreted by the ECU and it still reads and smells rich.

I unplugged the fan for troubleshooting. Got the engine temp up to 200 to 220 F and took it around the block. ECU still shows rich(.9v from o2).

Got my fuel rail/injectors flushed, just in case they were getting stuck open. No change in performance and richness.

Fuel pressure at rail shows around 35 psi at idle.

Torque shows 35%-ish load at idle.

Motor will occasionally pop in the exhaust an declaration.

As per the previous video, feels great driving and accelerates well.

ECU had a dent when I got my motor. Caused power issues for the ECU during initial install. After removing dent all "seems" fine. I have checked the board, but there seems to be no burn marks or popped caps.
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So, I am at the point of just replacing the remaining electronics/sensors that deal with fueling. I know the ECU could be an issue, how ever unlikely, and hope to save that for last as its a steep cost for a hope.

I keep thinking electronics cause it seems to mostly be an issue at idle, but I am shooting in the dark honestly.

Does anyone use torque that has a st215 motor? Curious what your o2 and load show at idle, just to see if I am barking up the wrong tree.

Any other suggestions?

Again, thanks for the help so far.

[Grrrrrrr!]

My temperature is a little low mostly cause I have a performance radiator and a fan that doesn't turn off lol.

Shouldn't make a difference. The fan and radiator can only cool the water that gets sent to the radiator, which if the engine isn't hot enough should only be a tiny trickle thru the jiggle valve on the thermostat.

Try pulling the thermostat and inspecting/bench testing it. It may not be closing fully.

[UtahSleeper]

Another small update with the troubleshooting I did tonight. This was with torque connected and engine running.

Disconnect MAP - Car died

Disconnected intake temp sensor on manifold - No change in output from ecu or idle.

Disconnected intake temp sensor pre turbo - intake temp changed to -40/nothing in torque. No other changes.

Disconnected sensor that has 2 vacuum lines going to it, on transmission side of motor - No change in output from ecu or idle.

Disconnected IAC - Idle went up, no other changes observed with load or o2.

Any other sensors worth checking? I know its not a very precise testing method, but figure of one of these sensors is feeding bad data then unplugging it should change what the ECU see's.

[UtahSleeper]

My temperature is a little low mostly cause I have a performance radiator and a fan that doesn't turn off lol.

Shouldn't make a difference. The fan and radiator can only cool the water that gets sent to the radiator, which if the engine isn't hot enough should only be a tiny trickle thru the jiggle valve on the thermostat.

Try pulling the thermostat and inspecting/bench testing it. It may not be closing fully.

I disconnected the fan for future testing as I am just idling. This has allowed the motor to get to "proper" operating temperatures.