Hi does any one know about file trims as I have been told these should run at optimum 0 when idling but mine run at 18-20 so I'm using 20% more gas ? could this be the MAS I asked my dealer for a price on the MAS and they said they had never sold one so I'm thinking they must never go wrong ?

 

Old thread but I finally got one of those OBD bluetooth adapters that actually worked and took a look at my car idling with torque and found my fuel trims on both banks were running rich (around -17 long term). Not so out of spec as to cause dummy lights but still the ECU is trying to lean out my car quite a bit.

I need to look again after actually driving around and the engine is at operating temperature/closed loop though... but if it's really that out of wack the same on both banks then the only things that can be wrong to cause the car to want to lean it out that much is something wrong with fuel pressure regulator or the MAF gone wild otherwise if it was something wrong with injectors etc. it would be much more likely for trims to be very different on each bank.

Can blow around $120 on a new OE denso MAF but I am tired of throwing money away guessing at parts - it is tempting though since it is so easy to replace (although one time I did try to get that sucker of the harness and failed the connector was so damn tight).

With no codes at all I am not really sure how to look at the OBD values to figure out if MAF or EGR are operating correctly, I don't even have any idea what sane values for the mass air flow rate might be. It hasn't been too many KM since I last cleaned the MAF with electrical contact cleaner either so I doubt it's "dirty" and even so I would have expected a dirty maf to cause a lean condition not a rich one (maf reporting less air than actual).

I suppose it is possible that both of my air/fuel ratio sensors are equally worn out and are misreporting the amount of oxygen in the exhaust, they are original to the car ... but have less than 70,000 miles. I will need to monitor those as well and I understand that they should switch lean to rich rapidly if they are good.


My mass air flow rate read between 2.5g/s to like 3.3g/s at idle, depending on whether it was idling at like 600 or 700 ish which sometimes I can't decide on. This seems like a pretty low reading.

Also, ambient temperature reported is -9C but intake air temperature is reporting at +9 on a warm engine, and drops to maybe +6 when I have the foot on the accelerator drawing in more fresh outside air. This seems wrong... I can see the hot engine warming the air coming in a degree or two maybe but not 15+C. I don't know if this is normal... meaning, I haven't tried to figure out what the math is to correct for air volume by temperature to see just how big of a difference just a wrong temperature reading from the IAT in the MAF would make to the reported flow rate.

Any smarty pants out there that can give me any idea whether this just looks like my MAF probably should get replaced let me know.

Oh yeah, torque reports the wide-range O2 sensors (AFR sensors) voltages as just sitting constant at like 3.3v or so until I punch the gas and they temporarily lower and then go back up to the constant value again.

Edit: Anyway. I found a new OE Toyota MAF on eBay for $85 shipped (after some negotiation) I am willing to risk shotgunning a new one in there even if there is a good chance the one in there already is fine for that kind of money considering the one in there now is a factory original it can't hurt. At least that will eliminate that part from the equation. Next I'll try to find the FPR and see if any fuel comes out of it when I remove the vacuum tube...

Gotta love this stuff, wish it was spring already and not still January temperatures outside.

 

First it sounds like you are just hellbent on bying a MAF for what appears to be no good reason. If a sensor reading was out of spec CEL would come on.

On a cold start, until the primary O2 (AFS sensor) heats up, engine must run in open loop and will run rich, It may be worth while to ensure you do this test after the thermostat opens up and engine warms up. It is pretty frigging cold to be doing this test in Toronto right now as well, note that cold air is richer in oxygen so that requires positive fuel trim as well.

Not sure where you figured it should be at 0, as per below between -20 and +20 is normal, the the mix has to be trimmed to deal with air temperature, flow and tons of conditions, by artificially trimming it down you probably would just cause misfire under load. And to be honest I am not sure why you are doing this unless you have a problem of some sort (it is unclear). If you are having rough idle, especially in cold weather, consider that the idle air bypass valve may be dirty/clogged. It is a stepper motor with a tiny hole that lets air come around the other side of the closed throttle plate. On my old car it was dirty, and on cold weather it would rough idle to outright stall on a red light. took it off and gave it a good scrub with a wire brush and carb cleaner, ran like butter after that. beware of the gaskets when you re-assemble.

DI cars do not have EGR valves, they have enough problems with carbon deposits as is. EGR function is achieved via VVT lift allowing for exhaust gas to just come back up into the manifold and be pushed back in (in a really simplistic way)

I am not sure which engine specifically you are looking at so here is 3GR-FSE just for fun to make you feel better.

2.1 to 3.1 g/s is within spec for idle
7.8 to 11.8 is within spec for 2500
AFS at 2.8V to 3.8V when idle
http://intranet.toyotaperu.com.pe/td...00pdn0gex.html

If you really want to fix things until something breaks, here is the test procedure for MAF
http://intranet.toyotaperu.com.pe/td...00q2d05xx.html

 

Thank for taking the time to reply. Yeah, I am talking about 3GR-FSE. First things first, if the cold air was the cause of the fuel trim wouldn't the trim be positive instead of negative? Shouldn't the fuel really not be trimmed all that much if the MAF is doing it's job - that is, telling the ECU how much and how dense the air coming in is - so it knows how much exact fuel is needed to burn? Thus, we have the issue that either the MAF is telling lies or the AF sensors are telling lies which leads to the trim changing by a large amount? Given that both banks are more or less equally trimmed, the MAF is the only part in the equation that serves both masters?

Yes, I am hellbent on fixing things until they break it seems. The reason I got interested in this is because I have suspected something was causing the car to run rich because of a fuel smell particularly on cold starts... (also one bank's rear o2 sensor randomly pops high voltage DTCs on me once in a while but that seems car wash related somehow and is a different obsession altogether). I understand the car will run rich on cold starts (open loop) and the cold doesn't help but sometimes it seems kind of excessive.

I suspected leaking injector maybe, so I looked at the fuel trims and saw that they were leaning out the mixture quite a lot. Thing is both banks long term fuel trim essentially end up to be equal at idle and one is out from the other by maybe -4 if monitoring running around - the chance of having equal numbers of injectors leaking equal amounts on both sides are kind of slim.

I've always read that acceptable long term fuel trims are supposed to be in the +-10 range not +-30 (the data list you linked to says normal range is actually within 30) and I took the fact that mine reach down to -20 as a sign something is on it's way out. Yeah it's kind of cold, it was around -9C when I looked at it today... but it has been much colder past -20C this winter and I'm not sure how much the temperature plays in fuel trim. Of course, they build an awful lot of room into the system before some DTCs will come up but operating within range of no dtc doesn't really mean that the car is running great.

Thanks for the link to that data list, very helpful. It is one thing staring at a long list of real time data and another trying to determine if what you're looking for is any good. Fuel pressure at idle for me is 4000kpa which is in spec of 3-5. That data list does say that the intake air temperature should be "Equivalent to ambient air temperature" and it definitely is not. Right from a cold start today through actually cruising it remained a good 8-9C warmer than the ambient temperature reading. Well, new MAF will tell me if that is just a normal quirk or a defect I guess.

i swear I have tried to find things on that site and sometimes it seems like pulling teeth to get to anything useful.

 

Hi BinaryJay,
I got the trims confused between the two posts, I didn't realize you were not OP, the OP was complaining about a positive trim. If you are getting a constant negative trim, then you are correct, O2 sensors are giving feedback that your exhaust is too rich so the injectors are reducing fuel, it could be various factors or problems. Might be MAF as you indicate, or could be other things like leaky/stuck injectors (although that could easily cause misfires under conditions). In other posts you complained about CEL coming up for the secondary (exhaust) O2 sensor, I understand there is a potential sensor voltage/ECU issue in the past with these cars, if the voltage from the exhaust sensor is wrong (consistently off) but still within spec, then your ECU may be constantly getting a "rich exhaust" reading from the O2 sensor, then it would be applying a negative trim to reduce the amount of fuel.

Again, if there are no real symptoms in terms of CEL or stuttering, rough idle/rough drive, misfire, etc.... you may just be chasing a non existent issue.

 

Yes, that issue with the secondary sensors there was actually a TSIB for before and they did that under warranty for me in the past so I do have the new ECU and new rear O2 sensor types that was supposed to solve that issue. All was fine on that front for a couple of years until I was driving through a major storm and that was the first time I got that high voltage code from the secondary sensor. It really does seem like that code popping off has something to do with the car getting really wet like going through an automatic carwash... I have yet to figure that one out, if it really is a water thing then wiring/harness somewhere is shorting out and getting wet when it shouldn't but WHERE is a mystery and it kind of seems like the type of thing that would cost a fortune in diagnostics to nail.

The fuel trims are still within spec, and the air fuel ratio reported is pretty close to being on the money so the engine is still running fine thanks to the wonders of modern computer controlled fuel injection but I still feel as if something is wrong somewhere for it to be having to lean out the injectors so much - I couldn't say whether whatever is causing it will stay static or if it's a slippery slope that will eventually lead to too rich DTCs.

At any rate, new MAF will arrive within a week or two so it's easy to at least throw that in and rule it out. If it makes no difference and my old one is still good, that part is used on so many Toyotas that it will be no problem for me to resell it as a used part maybe even locally for close to what I paid for the new one. If it doesn't do anything, the only other thing I can think of that would cause it to run rich on both banks would be a fuel supply issue (too much pressure) and these damned cars have EVERYTHING in the tank as one big module (filter, pump and pressure regulator are all together in the tank) so changing that end of the equation out will not be so easy and cheap if it ever comes to that (I'll wait for check engine lights for that job.....) My reported fuel pressure at idle is 4K right in between the range of supposedly normal values though.

 

I logged a 15 minute or so trip today using Torque including things like Mass Air Flow Rate and Engine RPM. I'm trying to compile it into some easier to digest form right now but there are some very suspect readings in samples I looked at.

The spec is:

2.1 to 3.1 g/s: Idling
7.8 to 11.4 g/s: 2,500 rpm

Here is a group of readings together that stuck out to me, the first number being RPM and second MAF Rate in g/s.

1673.25 32.59000015
2232 51.47999954
2377.25 55.47999954
2344.5 39.31999969

I don't know how accurate this is.... but in that 2500 rpm range, that flow rate is waaaaay more than it should be. Down closer to idle, it is closer to the spec but still on the high side. Across the whole data set though there are some inconsistencies where higher RPMs are producing lower flow rates in some cases etc.

In some ways this is encouraging that my shotgun diagnosis of MAF might have some merit especially since it is showing flow rate much higher than it should be - which would equate to the PCM wanting to inject more fuel, resulting in the AF sensors wanting to set the trim into negatives to compensate. I'm hoping to figure out how to graph the relationship somehow when I get time.

 

OK, I have a new and better theory now.

Cold start injector... I forgot this car had one. Basically it sprays fuel directly into the air surge tank on the intake manifold on cold start ups to help get her going. I believe that this injector leaking can cause the negative fuel trims on both banks that I'm seeing since that extra unaccounted for fuel would affect all of the banks more or less equally.

1) It shoots fuel directly into the airstream that goes to all cylinders.
2) It is not monitored by the ECU
3) Causes rich condition, AF sensors correct by leaning fuel trims

I'm hoping the root cause is that this injector, which basically just a valve that opens, is leaking fuel constantly into the intake manifold. This would support two sympoms:

1) When starting the car cold, the exhaust smells quite extra fuelly for a while. This would be all of the fuel that leaked out after the car was last shut off and is just sitting in the surge tank and/or leaked down into a cylinder or two.

2) Slightly hard starting - too much fuel sitting in one or more cylinders from the leak down. Car can't get a good air fuel ratio right away because of this.

3) When I shut the car off, and then turn ignigition on with engine (and fuel pump) off the fuel rail pressure as monitored with the scanner drops around 2 psi every 10-15 seconds. I am pretty sure it should stay pretty constant over a longer period of time.

4) If the fuel pressure leak down was caused by the injectors in the cylinders, it would have to be leaking more or less equally from one or more injectors on each bank which is not a very likely case.

Junked car cold start injector has been shipped to me for $60 and a set of new gaskets for everything is waiting for me at the local dealer. So I will wait for a nice day to get over my fear of cracking open fuel lines and replace it and hope that I can stop playing detective after that, at least for this particular thing... lol.

Anybody with a brain for this stuff, please feel free to either tell me I should not quit my day job or give me a pat on the back for my diagnostic skills.

What is the bright side to running with a leaky cold start injector on the 3GR-FSE? Well, it's almost like having port injection again -- suddenly the intake valves are seeing fuel with all of it's wonderful cleaners again. My intake valves may be sparkling again... if this turns out to be true, perhaps I'll keep the failed part around to reinstall for a month every few years to clean the carbon off hehe.

The downside is, crappier fuel economy plus whatever gets lost through leakdown between runs. I'm not sure how much actual fuel leaks out when the car is turned off until the pressure is relieved but I am guessing fuel doesn't actually compress a hell of a lot.

 

If anybody cares I've done the following:

1) Changed oil.

2) Replaced cold start injector... easier than I expected, there was like no fuel pressure in that line when I removed it, it wasn't messy and it only took me like 10 minutes. Used part from a lower mileage wreck on eBay.

3) Replaced MAF sensor, as usual very easy, like a 3 minute job. Looked like an official part, but you never know with these things on eBay - the actual sensor wires inside looked as much the same as I could tell by eyeballing it... but either way, car does not drive worse with it and unless I am just imagining things certain small amounts of hesitation when I step on it seem to have gone mostly away.

4) Ran a tank of Gumout Regane (PEA) through, currently running a second tank treated with the same stuff through now. I'm not exactly sold that this stuff really does any kind of perceivable good but whatever it doesn't hurt anything.

My fuel trims, at least at first glance, appear to be back down closer to 0 through a drive cycle with a slight bias to negative and a few spikes but nothing that got as low as prior when I first noticed the trims. Since I just went ahead and did all of the above in short order I'm not sure which one if anything individually was the smoking gun but hopefully that's that.

 

Good job, I would be curious if it improves your average efficiency.

 

I guess time will tell on that front. Haven't really noticed much so far.

 

I have the same situation with rich condition Gs450h.

can you please tell me how you solved it ?