Call of the week. Still unsolved. Air Fuel Imbalance Codes

Todd Technical Support Specialist Roseville, Minnesota Posted   Latest   Edited  
Question
Driveability
2015 Scion FR-S 2.0L (FA20) 6-spd (TL70)
Rough Run In Closed Loop
P119f - A/F Direct Imbalance
P119e - A/F Port Imbalance
P119a A/F Imbalance

Starts. Normal idle flair. Idles fine until it goes into closed loop. At that point, the fuel trims go to -30 (subtracting fuel) and the engine idles rough. The codes are P119A A/F Imbalance, P119E - A/F Port Imbalance, P119F - A/F Direct imbalance. 

This engine has both port fuel injectors and direct fuel injectors. It also has the ability to calculate the timing of the exhaust pulses going by the A/F sensor to calculate if the injectors are “balanced”. 

The problem started after a used engine (long block) was installed. The intake (including injectors) and sensors were swapped over. Smoke tested the intake for leaks, no leaks. Swapped MAF = same. Disconnect the front A/F (Air Fuel Ratio) sensor, the engine runs good​.​ It doesn't run better with a vacuum leak (unmeasured intake air leak forcing it lean), It doesn't run better with propane whiffed into the air filter box (forced rich). 

It runs rough on either port injectors or direct injectors when in closed loop and commanded to do so with the scan tool. Why does forced open loop make it run better? Why does the PCM think there is a rich cylinder (assumed because of the -30 Long Term Fuel Trim)? I thought the port fuel injector connectors were swapped thus when it saw a rich cylinder and subtracted injector pulse from that cylinder, it was making another cylinder lean. Verified injector wire colors. I have the tech scoping the port injectors to see what cylinder’s injector pulse is being reduced. 

What else should I ask the tech for? 

+3
Marlin Technician
Estacada, Oregon
Marlin
 

Before CL, what do the exhaust sensors read? Are they disagreeing about AFR?

Aren't their PID's for cylinder balance?

I am guessing that the A/F sensor was damaged before or during the engine replacement, but -30% seems too much to be based on this sensor. Why was the engine replaced? 

BTW, shouldn't there be a bounty on this, considering your position? ;-)

+4 Ð Bounty Awarded
Steven Technician
Huntington Beach, California
Steven
 

Todd, To understand the P 119 E/F we have to grasp the idea that the A/F Ratio sensor is one of the methods of capturing the main concern, an imbalance of cylinder contribution. the Crank sensor is also in play here. Without more information on the work done the condition of the engine and tune up we are working in the blind here.

+2 Ð Bounty Awarded
Steve Instructor
Irvine, California
Steve
 

Don't forget engines mechanical. The vehicle was an older version of AF imbalance. Is the O2 voltage clean without with out hash?

0 Ð Bounty Awarded
Steven Technician
Huntington Beach, California
Steven
 

Good point Steve! Even Spark plug configuration, brand and Gap can play in the P0119 E/F game.

For the life of me I cant see how a misfire will drive Fuel Trim negative.

Possibly there are more than one game in play, possibly Post Cat O2 info can help.

I believe that with more info we could find 1 root cause.

+1 Ð Bounty Awarded
Gary Owner/Technician
Owings, Maryland
Gary
   

Todd,

I agree with Steven Ethridge that the Crank Sensor is seriously in play here. The way I interpret the DTC set criteria, I believe the crank signal may be in play more here than the AFR. 

From what I understand, the FIRST test run by the PCM will be the crank sensor at or near idle, the SECOND test would be the Crank Sensor test AND the AFR sensor test.

I would think that Toyota is using the data from the first crank sensor only test and then from the loaded (rpm) Crank-AFR test to run through their alogorithm, in order to determine this problem. 

I would ask if you have performed a Cam/Crank Synch command on this car, (used engine, different crank sensor and clock position) as this would be CRITICAL to this rationality-based DTC.

On that note, (these being strictly rationality faults, not "hard mechanical/electrical sensor or circuit faults) I couldn't help but notice that in your case, even with -30 fuel trim immediately after closed loop, the PCM is NOT setting a rich code or any other fuel trim rationality dtc...?? (And the car runs fine with AF disconnected)

One would think that a true fault in the vehicle driving a negative 30 fuel trim would fairly dependably set that bank 1 rich code as well, but it is not. I don't recall ever seeing a car go to the -30 fuel trim "wall" without setting a few related dtcs.

Also, I would want to know WHICH code sets first (the a, the e or the f), as it looks to me like if we knew that, this would help with chicken and egg cause. If the idle one sets first, then looks like crank signal in play only but if AF one sets first, then would need to concentrate on both signals for more clues.

This brings me back to 

(A) Crank Sensor Synch or signal error

Or

(B) An air fuel ratio sensor circuit issue

Or

(C) The used engine is heavily (or less) deposited than the original engine and the PCM is telling you the truth about the imbalance. This heavy depositing could likely be either the valves/intake level of depositing being different engine for engine (you swapped the intake and injection from old motor, right?) Or the depositing could be in your injectors, and the "new" block/imbalance could be diminished injector performance in the other (replacement) engine. 

And I guess if these codes weren't there on the old engine, I'd go back over the work one more time then post some more in depth scanner data from the AF sensors, scope waveforms of AF and crank sensor and MAF would also be helpful so some folks can help noodle this with you further.

The air fuel data and or waveforms may tell the story.

Hope this helps in some way.

+1 Ð Bounty Awarded
Steven Technician
Huntington Beach, California
Steven
 

Here is some food for thought, #1 I agree with Gary on the wall, #2 Todd, can we look at post cat O2 sensor readings. The sensors are seeing information that doesn't fit, now the question is is it induced or accurate? The first iterations of this code looked solely at O2 sensors to see evidence of a torque imbalance. 

0 Ð Bounty Awarded
Steve Instructor
Irvine, California
Steve
 

Torque imbalance per ignition event.

Which bank or cylinder is causing the issue?

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Steven Technician
Huntington Beach, California
Steven
 

Wow, that narrows it down a lot Steve!

2015 Scion FR-S 2.0L (FA20) 6-spd (TL70)

P119f - A/F Direct Imbalance

P119e - A/F Port Imbalance

P119a A/F Imbalance

0 Ð Bounty Awarded
Darren Mechanic
West Allis, Wisconsin
Darren
 

Just wondering what the 5 gas is telling you...

+1 Ð Bounty Awarded
Gary Owner/Technician
Owings, Maryland
Gary
 

Exactly. Kinda need to know that one way or another since they all seem to be rationality codes.

0 Ð Bounty Awarded
Benjamin Diagnostician
Murfreesboro, Tennessee
Benjamin
 

I agree with taking a strong look at what the crank sensor is doing. The reluctor is wedged between the flywheel and crank. Could it have been possibly damaged? Have the tech scope the crank signal. 

+1 Ð Bounty Awarded
Rudy Technician
Montebello, California
Rudy
 

Ive never dealt with these specific codes. But after reviewing the information in Alldata, it looks to me like this is very much like monitoring for a misfire. Does the tech feel a misfire? Can he check a misfire counter in the scan tool?

Everything in the troubleshooting tree for theses codes is exactly what one would be checking for if it where a misfire....

0 Ð Bounty Awarded
Steve Instructor
Irvine, California
Steve
 

The misfire has not occurred yet.

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Steven Technician
Huntington Beach, California
Steven
 

We have 300 codes that haven't been set, leads me to believe Steve Caruso is right. this is something before misfire.

0 Ð Bounty Awarded
Steve Instructor
Irvine, California
Steve
 

Would concentrate on the negative fuel trim. Is this a dual injection system? If so look at the injector. 

+1 Ð Bounty Awarded
Marlin Technician
Estacada, Oregon
Marlin
 

I recommend reading the original post before replying; he answered your question in it.

0 Ð Bounty Awarded
Steve Instructor
Irvine, California
Steve
   

Good point Marlin.

Since the vehicle has two injectors per cylinder, fuel trim of -30% one of the injectors may be leaking providing that this not a bank issue. 

A couple of things come to mind: how are the "known" good cylinders doing. Since the codes could based off of two ignition events, could the others cylinders be throwing off the calculation?

How is the injector balance? Was a pressure drop test preformed? This is normally cylinder specific, have you swapped the other injectors to see if the problem follows the code? 

0 Ð Bounty Awarded
Marlin Technician
Estacada, Oregon
Marlin
 

I suggested monitoring the cylinder balance PID's, which seems like one of the most basic checks. Your mention of a possible leaking injector is a … point; however, I expect the system to be "smart" enough to react differently to that, since it would be leaking so little that it doesn't cause a misfire directly.

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Steve Instructor
Irvine, California
Steve
 

Well we gave Todd a lot of good ideas and food for thought. I am sure we will be looking forward to seeing what Todd finds outs and his explanation of everything. 

+2 Ð Bounty Awarded
Marlin Technician
Estacada, Oregon
Marlin
 

Yes, I hope that we get some … information out of this. Unfortunately, whomever he is working with is the critical factor at this point.

+2 Ð Bounty Awarded
Robert Diagnostician
Fair Oaks, California
Robert
 

With negative fuel trims either the engine is receiving too much fuel based on the sensor readings, a fuel leak into the intake, or a breathing problem that the engine is not breathing as well as the computer thinks. 

Need to look at valve timing, was the timing chain properly installed? Timing of the injectors? Timing of the Fuel pressure pulse with the injector? If the Chain is stretched and the injector plunger pulses at the wrong time the pulse width modulated pressure regulator cannot control Fuel pressure properly.

Sensor reading? Are the O2 sensors reading correctly? MAP, MAF, Temp?

With the Front O2 sensor unplugged and running good, are the emissions readings good out the back and have you used a lambda calculator on them to see if really running rich?

Good Luck

0 Ð Bounty Awarded
Todd Technical Support Specialist
Roseville, Minnesota
Todd
 

From the top.

Martin. This is a single bank flat 4. I assume the A/F ratio sensor is off line (not awake yet) before closed loop. I think the ECM is subtracting fuel from just one cylinder when it goes into closed loop which is why it “runs bad” in closed loop but “runs good” in open loop (A/F sensor disconnected). 

Steven. I interpreted the codes as a fuel imbalance not a crank speed (torque) imbalance. Post Cat O2 reading (graph) is a good question.

Gary. I did not think of a damaged crank reluctor at the flywheel. Do you think the -30 fuel trim is the PCM saying, “I took all the fuel away from a missfireng cylinder” (Assuming each cylinder is worth 25%) and it stops doing that when the A/F sensor is disconnected? I’ll try to get more scanner data from the technician. 

Steve. I do not know which cylinder is missing. I assume the fuel subtraction is happening to just one injector. I want the tech to DSO all the port injectors and applying Sesame Street methods, "One of these things is not like the other..."to find the cylinder the flip flop the port injector to see if it follows the injector. 

Darren. I’ll ask if a 5 gas is an option (most of the time it is not). 

Why does it misfire (in closed loop, -30 FT) on either injection system? The port injection system came over with the intake. I do not know if the direct injectors were swapped. I assume not because of the difficulty.

A breathing problem for a single cylinder sounds interesting. Less air (flow) but the same amount of fuel = rich. The PCM see the rich cylinder and subtracts the fuel back out but that causes a misfire? 

I’ll update you all when I know more. 

Thank you. 

0 Ð Bounty Awarded
Marlin Technician
Estacada, Oregon
Marlin
 

I am Marlin. I am a straight-shooter (gun brand), martins are birds. LOL.

Operation of the front sensor must be occurring before CL. Whether the PCM is subtracting from only one cylinder or not, will be observable by exhaust sensor signals and control PID's. I am certain that there are related PID's, though I have never work on this vehicle model.

+1 Ð Bounty Awarded
Todd Technical Support Specialist
Roseville, Minnesota
Todd
 

I will look. 

0 Ð Bounty Awarded
Billy Mechanic
Deming, New Mexico
Billy
 

I would stop and take the lean up against the tool box overview and ask "What changed" same ECM and injectors are the same and the calculation of the exhaust impulses have to have a base line which is provided by the only thing it can read is the crank position sensor. I would definitely scope the Crank/ Cam sensors against a known good to see if the timing has gone whacky . I would also check and make darn sure the replacement eng is what its supposed to be 

+1 Ð Bounty Awarded
Jim Curriculum Developer
Frederick, Maryland
Jim
 

I'm looking forward to hearing the resolution of this vehicle. Hope we get there. 

First a question. Is the P119a accurate or is it supposed to be a P219A? TIS does not show the 119a code in the menu for this application. This imbalance system detection for the D4-S has a couple of iterations. There are units with PIDS showing the imbalance level by cylinder and under what type of injection. They also split between idle detection where the CKP sensor is the primary as opposed to cruise conditions where the AFR is primary. Those systems will identify the cylinder by if you look at the PIDs for the idle condition. Under cruise it does not identify the specific cylinder as readily (if it is able) but identifies the injection system or both if applicable.

This vehicle can also detect by either the AFR or the CKP but does not offer the extra PIDs to help pinpoint. It normally idles, warmed up, on the direct injection system. If it detects and imbalance it will set the P119F and the P219aAat the same time. Then it will force the shift to the port injectors and check again. If it still sees an imbalance it will set the P119E and the P219A. This is why you can have all three codes "depending on type of failure". So we either are likely looking at an injection problem in both systems or something else. 

There should be four PIDs on this vehicle that could help identify if there is a specific cylinder involved in the issue to focus testing. Look at the Spark Advance of cyl "X" PIDs. The ECU can compensate ignition timing by cylinder to try to smooth compensation. I would monitor those PIDs as it starts to run rough and see if it is trying to advance or retard a specific cylinder when the fault occurs. Could be a way to gain a target of interest. 

+4 Ð Bounty Awarded
Steve Instructor
Irvine, California
Steve
 

Jim,

Great research on the subject. You have a good understanding of the code. 

From the information that I have on this, you are correct on the detection, AFR for rich conditions and CKP for the lean side. 

For conversation purposes, because this is such a big negative fuel trim, would it not be fair to say we have an over-fueling concern? Not knowing the condition of the replacement engine, IMHO we can not rule out a deteriorated engine. Yet engine is deteriorated aside, the over-fueling can either be an injector or leaking purge valve, only a few places where we can get HC's from.

IMHO, the smooth compensation is usually used for the lean side detection, predictive misfire PID. Would we not look at the Lambda PID value for an ECM's understanding of what is actually occurring with fuel. 

This is real tough concern, Coming to California Smog program in two weeks are PDTC. Since this code triggered the MIL, this is PDTC. The only way to clear the code is to drive it under that same condition as the failure. Throwing parts at this concern is not the answer, we must learn how to fix this problem. 

Jim, I sure hope Todd keeps us abreast on the diagnosis and final verification of this problem.

0 Ð Bounty Awarded
Jim Curriculum Developer
Frederick, Maryland
Jim
 

From SI on this specific vehicle the detection appears to be happening at idle using the engine speed fluctuation method. If it was only making the decision from the AFR it SHOULD.......only set the P219A code. The P119E/F codes are idle tests. It does not think the AFR is stuck because the P2195 and P2196 codes would put us outside of enabling conditions for the monitor. I see no listed fail-safe behavior for the set DTCs so I am not sure where the LTFT behavior is coming from at this point.

I have looked on their site and cannot find a record for this call at this time, so I assume it is still unresolved. ARRRGH. 

0 Ð Bounty Awarded