Fuel trims high on Toyota 4Runner

Fred Owner/Technician Maryland Posted   Latest   Edited  
Resolved
Driveability
1997 Toyota 4Runner 2.7L (M 3RZ-FE) 4-spd (A340E)
Fuel Trim High

fuel trims -20.34 both short and long ,bank 1 sensor .995 volts . fuel pressure 45psi (fuel pressure regulator on this model is a non working fuel pressure regulator , just there to plug the fuel rail) coolant temp 195f, bank 1 sensor 2 is .92v, MAF 2.91 engine speed 691 rpm Throttle pos . 10% Injectors are new Toyota . vapor canaster hose is plugged . What am I missing. Computer is the correct No. 

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Glenn Owner/Technician
Texas
Glenn
 

Hi Fred, I would check to see if the convertor is plugged. Do a back pressure test at idle then at 2000 RPM. Both short and long term are practically maxed out. Toyota monitors O2 sensor all the time, not just at cold start from what I have seen. If exhaust cannot get out this will max out the O2's. Don't dismiss a possible broken baffle in the muffler.

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Eric Mechanic
North Carolina
Eric
 

Is MAF 2.91, volts or gps?

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Fred Owner/Technician
Maryland
Fred
 

gps

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Joel Diagnostician
California
Joel
 

What type of canner do you used ? Can you post a graph of Scann data of those pids , with 3 different driving modes: warm idle , 2500 RPM free engine spinning ( no loads ) power brake if automatic transmission. About 10 seconds per each of them will be more than enough to insulate the issue if it is related to air or fuel . Maf GPS, fueltrims , rpm , engine load.

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Paul Owner/Technician
California
Paul
   

I assumed you meant -20 STFT and -34 LTFT. It should have a vacuum diaphragm fuel pressure regulator on the 1997 w/3RZ-FE per the service information and parts catalog. Fuel pressure with the vacuum disconnected should be 38-44 PSI. With the vacuum connected at idle, it should be lower than that. Maybe around 32-34 if I remember correctly, but it has been a very long time since I've worked on…

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Fred Owner/Technician
Maryland
Fred
 

The fuel trims were both -20.34

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Cmore Mechanic
Connecticut
Cmore
 

Agree with Paul about the fuel pressure damper. Regulator is on the left side behind/near p/s fluid reservoir. Either that is leaking or stuck open purge valve / stuck closed vent valve.

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Fred Owner/Technician
Maryland
Fred
 

The fuel pressure regulator vacuum hose on this model is hooked to the intake air silencer ,there for no vacuum to regulator . the regulator on this model does nothing the only reason it is there is to plug the hole in the rail ,the vacuum line is hooked up to the silencer so if the diaphragm leaks in the regulator fuel will go in the engine intake and it is not leaking . The computer is…

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Paul Owner/Technician
California
Paul
 

Hey Fred, It doesn't do nothing. It regulates fuel pressure. If you bypassed it, you would have no pressure. If you plugged it, it the pressure would be whatever the pump can produce. The “vacuum” port doesn't do nothing either. The pressure at the port will change fuel pressure, it just works on much lower changes in pressure. The fuel pressure specification is 38-44, presumably at sea level…

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Fred Owner/Technician
Maryland
Fred
 

Paul, This 4Rurnner sat for 3years and the person that had it wanted to fix it up for his wife . He replaced the plugs, wires, injectors with toyota injectors and fuel pump . The wife didn't want the 4Runner any more and he sold it. The person who brought it to me said he changed the o2 sensor and mass air flow sensor but the rich code kept coming back . I checked it and got the readings as on…

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Cmore Mechanic
Connecticut
Cmore
 

I would go with defective/faulty new injectors. Dirty throttle body would not cause engine to run full rich.

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Fred Owner/Technician
Maryland
Fred
 

That is what everyone is saying. Something wrong with the injectors.

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Cody Diagnostician
Illinois
Cody
 

Congrats on the fix. I saw the 10% tps reading and I was wondering that might sound a little high. Do you know if that pid changed? Carbon holding throttle plate open slightly maybe?

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Fred Owner/Technician
Maryland
Fred
 

I did not print it out and don't remember but the maf did change.

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Michael Technician
Indiana
Michael
 

Fred, I apologize for my previous post. This does not have a/fuel sensors. it's too old. It has all old school o2 sensors. A)I would find it hard to believe that you had 4 O2 sensors go bad at once. B) if you have ruled out pulling in fuel from external source like the purge line. C) You have good temp reading, tps reading, no clogged throttle plate, Vehicle load Pid will at least go to 85%…

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Michael Technician
Indiana
Michael
 

Your right it is just a spring and diaphram.

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Cmore Mechanic
Connecticut
Cmore
 

Fred I can't believe you said that, fuel pressure regulator does nothing. Really?

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Fred Owner/Technician
Maryland
Fred
 

The fuel pressure regulator on this model and year does not regulate the fuel pressure . the fuel pressure is the pump pressure 45psi . I called the identifix repair hotline and ask why the vacuum hose on the fuel pressure regulator was hooked to the intake silencer as per diagram on the hood . The silencer is before the throttle body and would have no vacuum there. He found info that this model…

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Cmore Mechanic
Connecticut
Cmore
 

Are you making this shit up?

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Fred Owner/Technician
Maryland
Fred
 

No not at all . This one was a tough one.

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Cmore Mechanic
Connecticut
Cmore
 

I was talking about the information you got from identifix

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Fred Owner/Technician
Maryland
Fred
 

No I don't know where he got this info, but I can assure you the fuel pressure regulator at the fuel rail does not do any thing but plug the hole. If there is a regulator it must be in the pump.

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Cmore Mechanic
Connecticut
Cmore
 

If there is a return line after the regulator then it absolutely controls the pressure. The only systems that use a regulator on the pump are single line returnless style.

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Fred Owner/Technician
Maryland
Fred
   

there is a return line may be it is factory set to 45psi and the vac line is there just to get rid of the gas if the diaphragm would burst. This makes more sense .When I talked to tech support we were talking about the vac line to the FPR and he probably was referring to the vac line and not the FPR.

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Glenn Owner/Technician
Texas
Glenn
 

Even though it is not leaking through the atmospheric nipple. (People keep using the term vacuum nipple, but it is not for vacuum) the tension spring has likely failed. This regulator works off of atmospheric (BARO) altitude pressure changes which are minor. Were the injectors actually from Toyota? For a 97'? Really? I would be concerned of aftermarket ones the dealer purchased from a local…

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Fred Owner/Technician
Maryland
Fred
 

This 4Rurnner sat for 3years and the person that had it wanted to fix it up for his wife . He replaced the plugs, wires, injectors with toyota injectors and fuel pump . The wife didn't want the 4Runner any more and he sold it. The person who brought it to me said he changed the o2 sensor and mass air flow sensor but the rich code kept coming back . I checked it and got the readings as on my…

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Michael Technician
Indiana
Michael
 

Congrats Fred, Definitely the throttle body, The first one I found like this really threw me. I just didn't know if Your Toyota was electric throttle or cable, and I haven't seen This problem (not that it couldn't happen) on cable operated throttles. I suggested Carbon on the throttle plate/bore in my first post. If I had understood your post, that said the tps was at 10%, I would have…

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Michael Technician
Indiana
Michael
 

Fred don't forget to reply to your own first post and select resolution, so every one knows what happened and tis is closed. Mike

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Fred Owner/Technician
Maryland
Fred
 

I think the regulator does regulate the pressure to 45psi but there is no vac at the regulator and it does not change pressure.

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Cody Diagnostician
Illinois
Cody
   

a lot of things can cause the a lean condition but only a few things can cause a rich condition. is that data from global or manufacturer? can't remember what year range was bad about substituted values. purge valve, leaking injector, incorrect O2 sensor, leaking fuel diaphram over reporting MAF. i've seen incorrect camshaft timing cause rich fuel trims(though i don't remember how much, don't…

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Fred Owner/Technician
Maryland
Fred
 

The injectors were replaced with the correct Toyota parts. Vacuum leak does cause trims and o2 to go lean Timing is at 10 deg. at idle 694 rpm

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Michael Technician
Indiana
Michael
 

Fred , 1)Unplug the front A/F sensor (wide band O2 sensor), see if it runs better. If so check the harness from the computer, the black and white wires should have around 3 volts (engine running) if so the ecm is doing it's part, suspect faulty a/f sensor(wide band O2 sensor). 2) check for extreemly coked throttle plate. On the drive by wire, it will cause a rich condition, not sure about the…

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David Diagnostician
Texas
David
 

Ecu could be too.

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Fred Owner/Technician
Maryland
Fred Resolution
 

This 4Rurnner sat for 3years and the person that had it wanted to fix it up for his wife . He replaced the plugs, wires, injectors with toyota injectors and fuel pump . The wife didn't want the 4Runner any more and he sold it. The person who brought it to me said he changed the o2 sensor and mass air flow sensor but the rich code kept coming back . I checked it and got the readings as on my…

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Paul Owner/Technician
California
Paul
   

My money is on the injectors. I thought that you had purchased them from Toyota, but it sounds like the seller had purchased them. Check out this listing for “4 OE fuel injectors on EBay.” Only $56 for a set of 4 injectors. Wow, a savings of $625 on the wholesale price! What a bargain. Notice the part number in the stamped on the side in the pictures? It used to be that sets like this were…

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Fred Owner/Technician
Maryland
Fred
 

The boxes looked genuine and the injectors looked genuine . I have seen this before . I avoid ebay and Chinese crap I'll try to find out where he bought them. He just said they were genuine Toyota.

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Joel Diagnostician
California
Joel
 

When I ask you the question about giving scan data in 3 Modes , we would have rule out aboutique waht conditions was running rich . But you did not send it.

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Milton Owner/Technician
Michigan
Milton
 

We had one a few years back. Very similar, but the v6. Also a slightly higher than normal idle. There was a closed throttle switch built into the tps. Cleaning throttle body and adjusting the switch didn't help, but replacing the throttle body fixed it. Everything was worn out just enough to bounce back and forth between on idle and off.

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