As you requested, I’m just throwing suggestions your way…

• Exhaust leak(s)
• Exhaust back pressure too high (clogged catalytic converter)
• Worn out transmission (due to age)
• Cheap gasoline (or too high ethanol percentage)
• Dirty fuel filter
• Dirty engine air filter
• etc.

 

As you requested, I’m just throwing suggestions your way…

appreciate the suggestions. here's my thoughts

• Exhaust leak(s) - i would think this would let air in the exhaust and cause o2 to read lean. short term fuel trims look to be in line (less than 7%) except on the initial acceleration where they spike when the afr does
• Exhaust back pressure too high (clogged catalytic converter) - i think i'm ok here...i would think this would cause reduced power throughout the range and acceleration is fine except for initial tip in. also looked at pre and post cat temperatures on the scanner and it was around 1000F pre and 600F post. seems reasonable but i could be wrong.
• Worn out transmission (due to age) - i thought about this though it feels like what i'm feeling is the motor wanting to stall. i guess if its the trans it will just get worse and will be obvious lol
• Cheap gasoline (or too high ethanol percentage) - has happened on multiple fill ups at different stations
• Dirty fuel filter - forgot to mention this is new as well, changed when i did the fuel pump
• Dirty engine air filter - forgot to mention new as well

 

I would check the mass air sensor if dirty can hesitate with no code.

 

yessir...tried cleaning it first...didn't help much so i replaced with a new denso one this week. the signal cleaned up a bit but didn't really help the hesitation. i figured this was the answer but no luck so far. ill probably keep throwing parts at it lol throttle body is next on the list.

 

so were you restricting the air through the filter? i'm not sure i understand

 

Have you tried disconnecting the battery and waiting 15 minutes and reconnecting? That fixed mine.

 

yes, have disconnected the battery a few times. it seems to reset because idle speed goes up after and takes a while to adjust.

i have a throttle body on the way so we'll see if that changes anything

 

replaced throttle body...still no change

 

Does yours do that while warming up then goes away? Mine has done that for years now. Cleaned MAF, cleaned throttle body, ran fuel system cleaner through, changed PCV valve, plugs, cat due to failure, etc. No codes. No issues otherwise. I've just accepted it's a quirk in the car. I feel like it would throw a code if something were really wrong with any of those parts. It seems to be much worse with AC on...maybe time for an evacuate and recharge? Who knows...

 

it does seem like it does it more while it is warming up...i could see having the a/c on making a difference since it adds more load and it seems to be just at that first point of tip in acceleration that the load is greatest it happens.
its more annoying than anything but it is my wifes car and it hesitates enough that if you were pulling out into traffic it can be problematic. no codes for me either.

the one thing i do see is a lean spike in the air fuel ratio that occurs when this happens. the ecm should command extra fuel when accelerating quickly...wondering if this is not happening for some reason?

another couple things i'm wondering about is the timing chain/tensioner and the variable valve timing actuator. could one of these be failing and the valve timing be off? it does have a rougher idle than it used to even with replacing plugs, coils, etc.

i may have to throw in the towel and take it to the dealership but i know that can be a hit or miss proposition.

 

3 grams at idle from a 2.4L seems a bit high. Off the top of my head I would expect it to be more like 2.4 grams! On modern cars at idle normally this is fairly close to the displacement in liters.

What is short term and long term fuel trim looking like? Any one cylinder out of line with the other 3?

My car is a manual transmission and it has done that since it was new with 4 miles on the clock. It normally does it when it is cold. I start my car up and wait about 30 seconds before putting it in gear and leaving my drive way. If it is going to do this it does it on the first hard take off after backing out of the drive way. Once it is up to temp though it does not do it.

My car is a 2003. 2 years ago I cleaned intake, throttle body and replaced all gaskets. I replaced the injectors and coils all with OEM suppliers when I fired the car up it idled at 2000RPM and even a relearn only brought down to 1100rpms for about 1 weeks when it finial dropped closer to the old 600 rpm idle. I replaced cam sensor and crank sensor. Maybe 3 or 4 years ago I replaced the fuel filter so I also put in a new Denso pump at the same time since it is all in the tank. Recently I replaced the under hood evap solenoid.

None of that ever effected that occasional lag in throttle response when cold. Never had a code for anything on this car other than Catalytic Insufficiency 2 times in almost 20 years, 1 heater circuit malfunction code and a single cylinder misfire code that went away on it's own and never came back.

I have often wondered about TPS and Throttle body but since it only happens when the engine is cold and rather randomly at that and it runs like new other than that I have left those alone other than cleaning the throttle body.

My wifes 2007 Camry same engine 2AZFE but automatic has never once done that. I have often thought that the flywheel is too light on the manual transmission 2AZFE and that the ECM programing is less than ideal as if they did not spend as much time on it. Prior to Tundra and wifes 2007 Camry every Toyota I have owned from 1982 own up have been manual transmissions. I have never liked how this engine is tuned in relationship to a manual transmission but it works and works fantastically so I just ignore it.

 

3 grams at idle from a 2.4L seems a bit high. Off the top of my head I would expect it to be more like 2.4 grams! On modern cars at idle normally this is fairly close to the displacement in liters.

What is short term and long term fuel trim looking like? Any one cylinder out of line with the other 3?

My car is a manual transmission and it has done that since it was new with 4 miles on the clock. It normally does it when it is cold. I start my car up and wait about 30 seconds before putting it in gear and leaving my drive way. If it is going to do this it does it on the first hard take off after backing out of the drive way. Once it is up to temp though it does not do it.

My car is a 2003. 2 years ago I cleaned intake, throttle body and replaced all gaskets. I replaced the injectors and coils all with OEM suppliers when I fired the car up it idled at 2000RPM and even a relearn only brought down to 1100rpms for about 1 weeks when it finial dropped closer to the old 600 rpm idle. I replaced cam sensor and crank sensor. Maybe 3 or 4 years ago I replaced the fuel filter so I also put in a new Denso pump at the same time since it is all in the tank. Recently I replaced the under hood evap solenoid.

None of that ever effected that occasional lag in throttle response when cold. Never had a code for anything on this car other than Catalytic Insufficiency 2 times in almost 20 years, 1 heater circuit malfunction code and a single cylinder misfire code that went away on it's own and never came back.

I have often wondered about TPS and Throttle body but since it only happens when the engine is cold and rather randomly at that and it runs like new other than that I have left those alone other than cleaning the throttle body.

My wifes 2007 Camry same engine 2AZFE but automatic has never once done that. I have often thought that the flywheel is too light on the manual transmission 2AZFE and that the ECM programing is less than ideal as if they did not spend as much time on it. Prior to Tundra and wifes 2007 Camry every Toyota I have owned from 1982 own up have been manual transmissions. I have never liked how this engine is tuned in relationship to a manual transmission but it works and works fantastically so I just ignore it.

Yeah nothing I have ever done has helped it. I think it is just something weird with the tune or something with the ECU. It'll get up and go if you stomp on it...even if it's lagging...Might take it a little longer but it'll get some encouragement

 

I bought my car with 4 miles on it and it has been doing it since new. Never does it when it is up to operating temp. nothing I have ever replaced on it has ever made a difference. While it does it when cold it does not always do it when cold it is still rather random. It is not as if the engine wants to stall or anything it is just that the command for more power just seems to lag for a second at random. It is a weird feeling and you definitely notice it when it happens. It is so random you would have to run live data in capture mode for weeks at a time every time you drove to have any hope of catching it.

Only ever had 3 codes in almost 20 years and they have all gone away by themselves.

I have always maintained that Toyota did a terrible job programing this ECM for manual transmission. It does not like idling in first gear at all never smooth at all. You really have to be moving for it not to jerk a lot. Trying to creep through a parking lot , traffic jam, or down a rough dirt road is mission impossible especialy if the parking lot has a 5mph speed limit. The stupidly low idle speed and light flywheel combined with vehicle's mass, tire size and gearing all work against. It is a ULEV certified combo with Federal Emissions so I am sure that and CAFE programing compromises are the issue.

It is super hard to adjust throttle in small increments precisely under 1000rpms. You will do it and the car will pull some throttle out this is no load in a manual transmission Camry. If you do it 2-3 time to that exact number it will ignore it and let you hold it there. Once above 1000rpms it is supper easy to adjust the throttle in 50-100 rpm increments with out the car fighting you at all. When you shift the ECM blips the throttle for you which means if you do that concisely you have to undo that! In the wifes automatic you get none of that! If this car had a cable operated throttle we would not see any of that at all. I would love to be able to see the fuel, ignition and cam timing maps when this is going on so I could see what is happening.

My wife owned a 2008 Saturn Aura now one of my college age sons drives that. The brakes are "smart" and they will add or subtract braking pressure based on what the car "thinks" you want under the conditions it is seeing. Anyone that has any skill at all braking in a car with out this sort of electronic nanny will notice it right away. Trying to stop in a precise spot is almost impossible. So if you tossed a quart on the line before a stop sign and could stop at or on that quarter 9 out of 10 times in a car with out brakes with voting right you would be lucky to do it 1 out of 10 times in that car. I am not talking about when you have activated ABS system due to conditions. So you are always chasing the braking you actual want because the car is reducing or adding braking pressure in spite of your foot position remaining constant.

The problem with throttle by wire, fly by wire steering and braking is that the system is only as smart and experienced as the person that wrote the code and tested it. Even on BWM's I have seen these systems piss people off and cause less than safe situations to occur. When they fail and they freq. do that is just one more thing that needs to be fixed. I have seen steering wheels spinning lock to lock with no one in the car in a not so smart car with electronic steering.

The fact that you can not feel these things in an automatic tells you how much loss and dampening is going on. My wifes 2007 is in great shape and lower milage and has been babied compared to my 2003 which I drive like I am playing Grand Theft Auto and her 5 spd automatic can not even get close to my car for MPG or acceleration but will idle through a parking lot as slow as you want to go. So there is definitely some strange things going on with the programing in the ECM manual vs Automatic. Also in her automatic car you can not feel the cams phasing much or at all but in a manual car when the ECM is adjusting the cam you can feel it clearly.

 

I'll have to double check st / lt fuel trims but i believe they were less than +/- 5%

i agree that the ecm programming is lacking. prior to this it was the opposite problem...throttle was too responsive...you couldn't ease into it...it would just jump out with little throttle input.

 

Here is a strange one -- was working to eliminate a PO446/PO441 that keeps recurring. Finally replaced the charcoal vapor canister on my 2003/2.4L (209K) which totally fixed the recurring CEL and stabilized fuel trims to 0 - 5%. The persistent low-throttle hesitation mentioned here also disappeared as a bonus. Now accelerates like new -- smooth and predictable.

Not saying the same will happen with your situation (especially if you do not have pending CELs), but something to consider before throwing in the towel.

 

Interesting. I don’t have a code but I get the hesitation when it’s warming up. It’s done it for years though. Was yours only doing it while warming up, or was it all the time?

 

appreciate the idea