If the displayed fuel trim value is a negative number, it means that the ECM is decreasing the injector pulse width to subtract fuel from the air/fuel mixture to lean out the air/fuel mixture because the input data it is receiving tells the ECM that the mixture is too rich. Maintenance items like a clogged air filter can cause negative fuel trims. Visual inspection is the first step in diagnosing fuel trim issues. Disconnected vacuum hoses or a damaged air filter housing can change the fuel trims. I would check first for a clogged air filter, then go from there. Something is preventing the correct amount of air from reaching the intake manifold, mot likely.

 

Perhaps incomplete fuel burn due to a bad injector pattern?
One big difference in the idle 2500 rpm vs 60 mph 2500 rpm is the throttle position necessary to achieve each. At 60 mph, you will be feeding more throttle to overcome wind and other drive frictions.

 

@Strega315

because the input data it is receiving tells the ECM that the mixture is too rich

A primary input is the O2 sensor; if it is fouled or dirty, then the average voltage tends to stay higher than the expected (.45V?). Monitor or capture a time history trace to examine the waveform: frequency, amplitude, average, etc, that might get you closer to the culprit

Was the engine up to full temperature during all the measurements? When cold the ECU is in open loop mode at idle. Need to determine if it is running closed or open loop.

What are the readings of the temperature sensors for coolant, engine air, etc? If the ECU thinks it is cold then it may be trying to run it a bit rich.

 

Toyota jp - Your right throttle position would be relative to rpm and engine load. Engine load is relative to vacuum ,map/maf sensor reading ( psia and map sensor voltage to computer) ,exhaust backpressure ,throttle position ,rolling resistance, and rpm. I think the only difference in 60 mph 2500 rpm and idle 2500 rpm is engine load and gear. Am I wrong about all this

Kenny bob -Always closed loop , always operating temperature 205f,

If reading this thread , skip posts 6-7 , since I made this edit( unless they made an edit)

 

Are you sure the throttle position would be the same?
Let say when you are going up an incline, what do you need to do to keep the engine at the same rpm/mph? You give it more gas!
The incline is the load you place on the engine!
Using rpm as a reference might not be valid in this case!
Just saying!

 

What New Echo Owner said...
If you are in gear and doing, let's say 60 mph, hold your foot steady on the gas so the pedal doesn't move and then slip the transmission into neutral. The RPM's will rise because you removed the load. Also makes sense if you recognize you consume more fuel going 60 mph at 2,500 rpm...so you know it also takes more air for the proper mixture. Bottom line is that the RPM doesn't tell you much about throttle position since different engine loads require different throttle positions to overcome. Gas could be to the floor going up a steep grade at 2,500 rpm or the gas pedal can barely be down to get 2,500 rpms in neutral.

 

The MAP sensor signal is one of the main signals for telling the computer what the air flow in the intake manifold is. The computer uses the air flow measurement (and other signals, like engine rpm, throttle position, coolant temperature and ambient air temperature, as Larry Carley puts it) with the front oxygen sensor signal to determine what the air-fuel ratio is. The computer then adjusts the fuel injector duration.

The MAP sensor voltages you provided in the other thread makes me suspicious that something is out of whack. I would be focused on the MAP sensor for awhile. Until what's going on with the MAP sensor is understood, I am not sure the readings you posted here for Fuel Trim (LTFT? STFT? Added together?) have much value, when it comes to discussing fuel trims under different conditions.

 

Sorry guys I made an edit to post 5 I think it is correct now.

Elle I made an edit to post 1 ( it's fuel trim already added together, short term was close to zero)

 

Sorry guys I made an edit to post 5 I think it is correct now.

Instead of editing your original posts, you should put up a new post with the corrections, so the whole thread would make more sense!
If you had made the changes before anyone had responded, that is a different story!

BTW, it would be helpful if you post the ST and LT FT numbers separately!

 

the throttle position is open more at 60 mph 2500 rpm than idle 2500 rpm, and there is increased pressure at air filter.. (due to engine load(rolling resistance) ) This means higher map sensor reading( intake manifold pressure) , higher engine load, higher voltage signal from map sensor to computer, higher exhaust manifold pressure, higher ported vacuum, and lower intake manifold vacuum at 60 mph 2500 rpm

Am I right does this mean higher map sensor reading (intake manifold pressure), higher engine load, higher voltage signal from map sensor to computer, higher exhaust manifold pressure?, higher ported vacuum, and lower intake manifold vacuum at 60 mph 2500 rpm than idle 2500 rpm? Yes

What about the vacuum at the fuel pressure regulator at 60 mph 2500 rpm , would it be lower than idle 2500 rpm ? No?, ported vacuum has opposite effect as intake manifold vacuum?

This thread 12 Symptoms Of A Bad Fuel Pressure Regulator: Diagnostic Tests! - Autocornerd
Verifies this post # and post #5

Manifold vacuum and ported vacuum:
1. Manifold vacuum :
Comes from between the manifold and throttle body ( should be a steady reading somewhere between 17-22 in hg ,depending on elevation and high low pressure systems, on all engines)
Highest on deceleration, then idle
At idle, the more vacuum ,the better
Will rise during snap throttle test if rings are sealing good
Cranking vacuum should be 3-5 inhg on most engines
If cranking vacuum is over 3 inhg, engine will start and run
If cranking vacuum is near 0, egr valve is stuck open (or maybe it could mean something else? ) and engine will not start
2. Ported vacuum:
Vacuum is ported if port is located between air filter and throttle body
Can be equal to manifold vacuum , but can never exceed it
3. Relation between manifold vacuum and ported vacuum:
Throttle opening affects ported vacuum opposite to way it affects manifold vacuum. At closed throttle engine running, manifold vacuum is high but ported vacuum is close to 0, so when increasing rpm (opening throttle plate more) the vacuum reading at manifold should decrease but increase at port.
I think when you have both manifold vacuum and ported vacuum ,in the equation, as both being a source of a lines( hose, tube, pipe, whatever) vacuum supply you will have close to 0 inhg vacuum when engine idling due to the ported vacuum, and you will have less than 0 inhg vacuum when engine rpm is increased due to the manifold vacuum ( so when you have both manifold vacuum and ported vacuum as a lines vacuum supply, the vacuum reading will always be close to 0 regardless of engine rpm) ?

Air relation to throttle position:
1. If open throttle: low intake manifold vacuum, high ported vacuum (higher than close to 0), high intake manifold pressure (high map sensor reading), high engine load, high voltage from map sensor to computer, high exhaust manifold pressure?
2. If closed throttle: high intake manifold vacuum, low ported vacuum (close to 0), low intake manifold pressure (low map sensor reading ), low engine load, low voltage from map sensor to computer, low exhaust manifold pressure?


Echo- the st for all 3 idle rpm was the same it oscillates fast between 2 lean and 3 rich (live data) so I choose zero for the addition of st lt. The short term for 60 mph 2500 rpm is 3 rich (freeze frame data)

 

the throttle position is open more at 60 mph 2500 rpm than idle 2500 rpm, due to engine load ( rolling resistance),

True.

And there is increased pressure at air filter.

True. But also the throttle butterfly valve being open more increases the pressure that the MAP sensor is seeing.

This means higher map sensor reading and lower vacuum at 60 mph 2500 rpm

True. To elaborate: The higher the absolute pressure at the MAP sensor, the higher the voltage signal from the MAP sensor to the engine computer, and the lower the vacuum is. The air the engine's pistons are pumping from the intake manifold/plenum (promoting vacuum in the intake manifold/plenum) is not enough to compensate for the wider open throttle valve. The absolute pressure at the MAP sensor rises.

Am I right does this mean higher map sensor reading and lower vacuum at 60 mph 2500 rpm?

Yes, you are correct. To reinforce this see Manifold Absolute Pressure MAP Sensors . Larry Carley has been around for decades and is one of the finest automotive technology writers around, AFAIC.

As has been noted, the black exhaust and other signs are that your Camry's air-fuel mixture is top-heavy with fuel. The oxygen sensor is sending a signal to the computer that reflects the rich air-fuel mixture. The computer tries to reduce the richness. The negative, total fuel trim indicates the computer is doing what it is supposed to but so far, is not succeeding. The computer commands a shorter duration for the fuel injectors. Less fuel is added. With less fuel the driver will see signs of power loss. For some reason, the proper balance between desired power and the air-fuel ratio cannot be achieved.

What about the vacuum at the fuel pressure regulator at 60 mph 2500 rpm , would it be lower than idle 2500 rpm ?

[Edit, based on the vacuum diagram for the OP's Camry] I agree the vacuum should be lower (meaning the absolute pressure is higher) at 60 mph, 2500 RPM, compared to idling at 2500 RPM.

This Camry has a distributor, right? Have you checked the timing?

Edit: Attachment now shows the vacuum hose routing diagram for tmauldin's Camry.

 

I assume you are getting no codes for other sensors...are you suspecting a vacuum leak, ECU issue, fuel delivery system issue or still trying to narrow this thing down? You are really out of my knowhow now!
Best I can suggest is to make sure you don't have something simple before you look for a more complex issue. People have found rat's nests in their intakes for example. The shortened fuel delivery pulse at idle might just be an outlier data point but the one at highway speeds looks like it's trying to reduce fuel to compensate for not being able to get enough air.....or to compensate for too much fuel. Seems like reduced fuel would be a more likely scenario but, as I said, I'm in over my head now. I THINK the fuel trim is an ECU response to data from your O2 sensor indicating incomplete burn of fuel....I think that would only happen if you either inject too much fuel, there isn't enough air available to fully burn the fuel, or you have one or more cylinders that are not firing and burning the fuel. In that case, you should get a misfire code.

Ok, that's it for me....I'm going to stand over here by the fender and watch now!

 

No codes. I'm suspecting fuel and or air. No misfires. I'm trying to relate stuck open fuel pressure regulator to running 20 percent rich at 60 mph 2500 rpm but I think if the regulator were stuck open the engine would be running lean at 60 mph 2500 rpm unless I have more than one problem.

 

What specific problem are you having that lead you to look at the fuel trims in the first place? Black smoke out of the tail pipe? Bad fuel economy? Running rough? If there are no codes why do you think anything is wrong. Have you checked the inlet pipe between the MAF sensor and the throttle body? Unmetered air entering the engine past the MAF sensor will make the ECU inject more fuel to compensate for the air leak because of what the A/F sensor is reading.

 

This car has a map not maf. Mpg is down, black smoke , smell gas, long term fuel trim at 60 mph 2500 rpm 22 rich, fuel pressure did not increase when disconnecting fuel pressure regulator vacuum hose,

 

It does not have the vsv for fuel pressure regulator and the vacuum the fuel pressure regulator sees is not the same the intake manifold sees, at least that's how it is on this car ( I don't know if that's normal or not) ( it reads 0 )

It has a good distributor, the timing is 5 advanced degrees