High Positive Fuel Trim -sometimes-

Jonas said:
Oil consumption. New pistons put in and new cat. Old cat was shot from oil/misfires.
Click to expand...
Ok. You mentioned shaky idle. Is that where the fuel trim question comes from? Not unusual for this engine to be shaky. Seems like every 4cyl I've owned shakes a bit. I could have missed this in the comments disregard if already mentioned..
Check the dog bone mount for movement when you go into gear. Common to eat them up. Recheck vacuum related parts that could have gone back wrong during reassembly. Spray carb cleaner around IMG, TB, injector holes.

Try this if you haven't already


Edit: oops this is not a Camry. But will this work.. only one way to find out
 
Another thing, the o ring that seals the MAF is split. It seems to be in there snug, but I wonder if that would have any effect. I can't find a replacement. This is what it looks like:
1615481574514.webp
 
So, just to recap my fuel trim gradually goes up throughout the day and the car also gradually idles worse and worse. It's the strangest thing. This morning the car ran perfect for about an hour and my long-term fuel trim was + 2.3. As the day went on it went up to 5.5, 7.0, and is now at 10.1 with a noticeable vibration in drive or Park.
 
Is the dogbone the one on the top left when facing the engine by the oil cap? I'll check that for excesive movement. I've already replaced another motor mount and the trans mount which made a significant improvement.
LeakySeals said:
Ok. You mentioned shaky idle. Is that where the fuel trim question comes from? Not unusual for this engine to be shaky. Seems like every 4cyl I've owned shakes a bit. I could have missed this in the comments disregard if already mentioned..
Check the dog bone mount for movement when you go into gear. Common to eat them up. Recheck vacuum related parts that could have gone back wrong during reassembly. Spray carb cleaner around IMG, TB, injector holes.

Try this if you haven't already


Edit: oops this is not a Camry. But will this work.. only one way to find out
Click to expand...


14Accent said:
Right, I was just using the 1.8 as a case study. I personally haven't seen any issues with the 2.4 and intake gaskets. The vibration between 800-1200 could be almost anything, but you say the engine was rebuilt? I assume that means they completely removed it?

I only ask because it's common to not get the engine quite square when it's reinstalled, and that can send weird vibrations through the chassis. This was much less of an issue when most cars had the powertrain mounted to a subframe, however when the motor mount bolts directly to the frame fail it can cause very strange harmonics.

If you're positive that the problem started after the engine work, an easy test is to loosen the mount to frame bolts 5-6 turns, start the engine, rev it a couple times, then tighten the bolts while the engine is still running. This can help center the powertrain on it's mounts, and can help a lot with vibrations.
Click to expand...
Which ones are the mount to frame bolts? The motor mounts? Which one(s)?
 
When I go to "test component" on my OBD, it says "evaporative system leak test failed." No CEL. Any thoughts on this? I'm taking it to get looked at tomorrow, but I'd like to give my guy as much useful information as I can.
 
Jonas said:
When I go to "test component" on my OBD, it says "evaporative system leak test failed." No CEL. Any thoughts on this? I'm taking it to get looked at tomorrow, but I'd like to give my guy as much useful information as I can.
Click to expand...
Possibly a pending evap code. A leaky,failed evap purge solenoid near the throttle body or in the top/side of intake can let tank vapor in freely from the charcoal cannister. This may cause a rich run condition that worsens as engine and fuel tank warm as you drive.

Is the car hard starting after a hot restart or just after you top up the tank? Does the valve hold vacuum if you hand pump it with a tube and Mityvac pump?
 
I seem to have a lean condition since the computer is adding fuel. My fuel trims also go down when revving and even more when driving under load suggesting a vacuum leak, but I can't find anything. Sometimes the car takes up to a second longer to start when hot, but starts up fine. I don't know where this valve or solenoid are, but I'll look them up.
 
LeakySeals said:
Ok. You mentioned shaky idle. Is that where the fuel trim question comes from? Not unusual for this engine to be shaky. Seems like every 4cyl I've owned shakes a bit. I could have missed this in the comments disregard if already mentioned..
Check the dog bone mount for movement when you go into gear. Common to eat them up. Recheck vacuum related parts that could have gone back wrong during reassembly. Spray carb cleaner around IMG, TB, injector holes.

Try this if you haven't already


Edit: oops this is not a Camry. But will this work.. only one way to find out
Click to expand...

What does IMG mean?
 
*update* I took my car to my brother who did the rebuild and he didn't replace the downstream 02 sensor. He said that may be the problem. It reads as high as .8 volts and as little as .115 volts sometimes, but doesn't change quickly/often. It is also 13 years old with 183k miles on it. Would the downstream sensor have any effect on fuel trims? My LTFT is averaging +10.9 lately.
 
Jonas said:
*update* I took my car to my brother who did the rebuild and he didn't replace the downstream 02 sensor. He said that may be the problem. It reads as high as .8 volts and as little as .115 volts sometimes, but doesn't change quickly/often. It is also 13 years old with 183k miles on it. Would the downstream sensor have any effect on fuel trims? My LTFT is averaging +10.9 lately.
Click to expand...
For $30 it's worth a shot to change. They are wear items at about 200k kms. Could be your cat is about to go though. Haven't read whole thread so don't know if it's been replaced.
 
2009Caraman said:
For $30 it's worth a shot to change. They are wear items at about 200k kms. Could be your cat is about to go though. Haven't read whole thread so don't know if it's been replaced.
Click to expand...
The front cat is new, the second one is original.
 
This may be far-fetched, but my alternator puts out about 13.4-13.7 volts at idle. I've read from people with the same car/engine that their alternators put out over 14 volts. Alternator is also original. Could the charging system have any effect on fuel trim especially at idle?
 
*Update* I definitely have a vacuum leak. I can't tell exactly where it is because it's behind the engine by the firewall, but I sprayed starter fluid by the #1 injector and it bogged down and fuel trims went negative. My only thing is I can't tell if it's an injector o-ring seal (could fix myself) or the intake manifold (PITA). I also hear hissing around that area, but can't tell if it's coming from the injector or if the intake is leaking in that isolated spot. Any guesses as to which one is more likely on the 2az fe engine?
 
You must log in or register to reply here.

Similar threads

0
Long Term Fuel Trim at 20% 04 Mazda 3 2.3L
2
Replies
27
Views
744
00scrub
C
2009 Silverado Misfire
Replies
5
Views
377
Oliveoil2
B
2014 Honda pilot live stream O2 data questions
Replies
1
Views
144
Brybo86
R
EuroVan fuel pressure really high
Replies
4
Views
179
clinebarger
W
Possible throttle body problem, 2007 Mustang GT.
Replies
5
Views
685
wtd
Back
Top Bottom