2001 Toyota 2.2 MAP engine high LTFT @ idle

This 2.2 inline 4 cylinder runs great but has high LTFT at idle, around 15, goes down almost as soon as I bring it off idle. The IAC count is around 41, which is the same as my Toyota truck with a V6, so it doesn't seem like a vacuum leak. I pinched the brake booster line anyway just for interest cuz I think it's going bad and had about a 2 or 3% improvement, I let off it and pinched the vapor can line and it got slightly worse, so it was probably in purge and burning vapor. If the IAC count was low I'd be looking for a vacuum leak, but it's not. Anyone have any suggestions on this? Running down the road the STFT + LTFT is almost dead on zero across all rpm ranges, it get good gas mileage and the AFR and O2 numbers are great. Just seems like that LTFT is pretty high at idle.

TIA,
Gary

First, I think you're confusing IAC Counts with IAC duty cycle. You even mentioned a percentage increase when pinching the brake booster hose.
Second
A vacuum leak would lower the duty percentage and would not cause positive fuel trim numbers at idle.
Third
Look for a sticking open EGR. Is the idle rough?
Look for a head gasket issue
Look for a timing issue
Possibly a sticking open canister purge valve (LTFT would change as the canister is depleated)

ScannerDanner wrote: First, I think you're confusing IAC Counts with IAC duty cycle. You even mentioned a percentage increase when pinching the brake booster hose.

Thanks Paul and, yes, I should've been more careful with my terminology, it is a percentage that is displayed so I should've said IAC duty cycle. But the percentage I was referring to was the LTFT, not the IAC. So, pinching the brake booster line caused the LTFT to drop a few % and subsequently pinching the cannister line made it a bit worse so it seemed to be burning vapor at that moment. I will have to do it again to see what pinching either line does to the IAC %; I can't remember if was watching that, I was focused on the LTFT but for a MAP engine that's probably not the right thing to be focused on I guess. Being a MAP engine it seems like a small vacuum leak shouldn't affect the LTFT; I can kinda understand why the fuel vapor laden draw from the cannister would drop the fuel trim it a bit though.

ScannerDanner wrote: Second
A vacuum leak would lower the duty percentage and would not cause positive fuel trim numbers at idle.

So, I had that part, I had just reviewed the video in which you show that going on. I only have my other Toyota as a guide and its duty cycle is really close to this one.

ScannerDanner wrote: Third
Look for a sticking open EGR. Is the idle rough?
Look for a head gasket issue
Look for a timing issue
Possibly a sticking open canister purge valve (LTFT would change as the canister is depleated)

No rough idle, it runs great, getting good fuel mileage and all. I squeezed the diaphragm on the EGR and opened it maybe 1/32", only a tiny bit, and the idle reacted immediately so I can only say that it is moving easily but I need to pull it and check the seat and see if it looks like it's sealing ok but I did give it that quick check. I should also pull the vacuum line off and make sure the VSV isn't leaking and pulling it open some.

When you mention timing I assume you mean valve timing, I replaced the timing belt a couple of years ago so it was good then and if it was off a tooth it'd be running like crap. I can't remember off hand if that one has any variable valve timing I will look at the manual and see if it shows anything about it. I don't think it does. I put in new plugs and wires and resealed the spark plug tubes last year too as they were leaking a lot of oil.

Thanks again Paul,
Gary

No VVT, the thing I was thinking of is an anti-backlash device. I reran the tests I did before but I unfortunately saw too many numbers to keep track, I'll do it all again with a notepad and pencil handy. What I do remember is that when I started the IAC was between 29 and 30, that's a big drop from 41. I pulled the brake booster line and plugged it, the idle was normal and the STFT went to about -6% iirc. Then pulled it and left it off a while, while it was off the STFT went way up and so did the idle, the IAC only dropped to 23. The idle was about 1450, I didn't understand why the IAC didn't bring it down further.

The main takeaway from tonight was the IAC was 10% lower than before and the LTFT was 6% higher; just barely below 20, occasionally with the STFT added, total fuel trim was over 20%.

I made a table of the results and attached it as a jpg (I can't find a way to insert the picture itself):
1) I first ran for several minutes with everything normal
2) Then with the brake booster line off and the vacuum line capped
3) Then with that cap removed so I had a big vacuum leak
4) Then with the booster hooked up again and the evap purge line pinched off
5) Finally a few more minutes with everything back to normal

I was letting it run for about 90 seconds or so at each step, something seems wrong with that LTFT stuck at 14.8. I went out of Enhance Data and looked at the Generic OBD2 and saw that same number though, so it seems real, not a substituted value. The STFT went negative with a vacuum leak, not what I expected to see... unless it is interpreting this as a demand for power? But after a few seconds it seems like it should've corrected the LTFT. I should've had the Injector pulse width up too, I just looked again at Section 1, page 5 and see that is one of the ones that is shown there. and it gives and idea of what the computer is "thinking".

Also, it sure seemed odd that the idle was way above normal during the vacuum leak part of the test and yet the IAC% was still 24, it didn't seem like it was even trying to bring it down.

rn8849 wrote: The STFT went negative with a vacuum leak, not what I expected to see... unless it is interpreting this as a demand for power? But after a few seconds it seems like it should've corrected the LTFT. I should've had the Injector pulse width up too, I just looked again at Section 1, page 5 and see that is one of the ones that is shown there. and it gives and idea of what the computer is "thinking".

Also, it sure seemed odd that the idle was way above normal during the vacuum leak part of the test and yet the IAC% was still 24, it didn't seem like it was even trying to bring it down.

Two things:
1. Welcome to Speed Density engines with vacuum leaks! It does not cause a lean condition in most circumstances due to MAP sensor signal changes.
2. Idle will be high with a vacuum leak on a MAP (speed density) engine. MAP sensor "sees" the psi change in the manifold, signals the ECM that there is an additional load, ECM then commands more fuel. So you have more air and more fuel = high idle.
The IAC duty cycle at 24% is most likely a fully closed command, so the reason it didn't drop the percentage any lower, is because it is already closed all the way. Spring pressure is higher than magnetic field strength at this point.
To compare, fully open (mechanically) may only be 65%. Make sense?

So I went looking for some known good data to see what a typical IAC runs on this engine. Closest I could come was a '97, but I really don't think they changed all that much between years.

Known good vehicle, in for an oil leak fix.

www.scanshare.io/share/EIUJhCDPLkeFnTvpICYn5w#0,1,3,7,9,10,18



The changes in idle speed are from the cooling fan cycling. That 24% IAC number sure does seem low in comparison

Yeah, that sure adds some perspective

That 24% IAC number sure does seem low in comparison

I think he made a vacuum leak when he saw that number and was questioning why the % wouldn't drop any lower with the idle still being high.

Tyler wrote: So I went looking for some known good data to see what a typical IAC runs on this engine. Closest I could come was a '97, but I really don't think they changed all that much between years.

The changes in idle speed are from the cooling fan cycling. That 24% IAC number sure does seem low in comparison

Noah wrote: Yeah, that sure adds some perspective

ScannerDanner wrote:

That 24% IAC number sure does seem low in comparison

I think he made a vacuum leak when he saw that number and was questioning why the % wouldn't drop any lower with the idle still being high.

Paul, that 24% was after I blocked off the brake booster but before, during and after I created the vacuum leak. I am really questioning the data I am getting. After seeing this I went back and reviewed Matt's (Schrodinger's Box) 4 videos on the Case Study from Hell in which his IAC was messed up on his TransAm; not because it was in regard to an IAC but because I remembered that he was getting data that he couldn't trust. I am using a Solus Edge to get this data, as I stated before, I am using Enhanced and Generic. I am going to connect my old Actron just for interest and see what it says.

But, speaking about Matt's IAC issue, he was getting whacked out LTFT because of a bad IAC, I am getting whacked out LTFT too so I am at a minimum paying close attention to the IAC. My question is why did Matt's IAC wreak such havoc on the LTFT? It's not unmetered air coming in afterall and the idle was even correct. I can only assume that computer was choosing a cell from the fuel map based on what IAC count it was using and that count wasn't really where the IAC was because it turned out to be faulty. And I say that partly because he says that at least for a while he was seeing the LTFT jump way up when the A/C was turned on and drop when it was shut back off again. So, again, this may not be what my problem is, but I would like to understand why his car was acting that way in response to a bad IAC.

Thanks Tyler, Noah and Paul,
Gary

Tyler,

How did you insert the jpg? I couldn't figure out how to do anything other than just attach it.

Gary

rn8849 wrote: Tyler,

How did you insert the jpg? I couldn't figure out how to do anything other than just attach it.

Gary

No problem! It's actually just a couple more steps past uploading the attachment. Once you've attached the file you want, you hit "INSERT", and it produces some boardcode wherever the cursor is.



The boardcode produced looks something like this:

After that, just move the boardcode wherever you want the photo to show up!

About your Camry... This is a long shot, but maybe try blocking off the PCV hose? I've seen it a couple times on MAP engines where a stuck open PCV valve will suck air through valve cover gaskets/crank seals/anything it can, and result in strange IAC behavior.

I'm not saying it'll account for the fuel trims, but it might account for the low IAC % at idle.

Thanks Tyler, I was on the right track, when I saw the barcode I thought I'd done something wrong because the picture didn't show up right away.

I didn't get to work on the car much this weekend because me wifey needed to use it. I did have a few minutes on Sunday to swap in a MAP sensor out of a GM that I had lying about, the car spazzed out about it though, so the calibration must be a lot different. The voltages didn't seem that much different to me but the ECM apparently had a different opinion.

Hopefully I can tear into it this weekend.

Gary

this is a test:

:lol: :lol: :lol:

I love brand hate like this! Personal fav: "Dodge, in the dictionary: To avoid."

Tyler wrote: :lol: :lol: :lol:

I love brand hate like this! Personal fav: "Dodge, in the dictionary: To avoid."

Hahaha, that is great!

On the flipside is brand love, if you have a few minutes watch this video of my ride to work one day. Earlier this summer we have some wicked flooding in Houston. For reference here is a picture of the dimensions of those barrels we are passing by...




I measured debris left on my A/C condenser at the water line when I got home that day, it was at about 30". I would not have believed a stock Tacoma Prerunner could do that if I hadn't experienced it myself. I love my Toyotas. At 4:51 I stop for a few seconds and ask myself if I'm and idiot, once I decide the answer if yes, I proceed on, lol. All of the electrics, the alternator, the COPs, etc are all above or nearly above the valve covers. The air intake is at the highest possible point inside of the left front fender. There was about 1/2" of water in the bottom of the air cleaner box so I changed my filter and later my oil just for good measure. Checked my rear differential and automatic fluids, they were ok. I don't know why the water didn't come up around the floor shifter, but it didn't and none came in the door seals.

Do you get a flare up on start up? Does the computer bring the idle back up to the correct RPM when you hold the steering on full lock and switch all the accessories on? This is a very quick IAC test that may point you in some sort of direction

Richey.brown wrote: Do you get a flare up on start up? Does the computer bring the idle back up to the correct RPM when you hold the steering on full lock and switch all the accessories on? This is a very quick IAC test that may point you in some sort of direction

Richey, I haven't tried cramping the wheel against the lock but I do know that I get a flare at startup and when the A/C cycles on and off. I wasn't as much concerned that the IAC wasn't able to bring the idle up, what I was and am surprised by is that it doesn't take it down when I pull the brake booster vacuum line off. Paul explained that though I see 23% during that test it is likely that the spring pressure may actually be overcoming the then weak magnetic field at that low percentage and it may actually be as low as it can go.

Also, I had wondered "aloud" so to speak a while back that perhaps the fuel pressure regulator may be dropping the pressure lower than it should while the vacuum is really high at idle... well, that's out, I learned that the regulator is in the tank on that car so I can cross that off the list of possibilities.

Thanks again guys, I will try to pull that EGR this weekend and make sure it is seating properly.

-Gary