[Jess8591]

I have a 2000 Camry -V6 1mzfe engine
Owned this car just over two years, the problem with this car is for months it will drive great no problems at all and then suddenly it starts to hunt extremely bad and loses some power in throttle, revs out further really struggles and smells like it's over fueling. It does this for about 2 weeks off and on everytime I drive it then stops and drives great for months again and then it comes back and so on..been to many different mechanics and tried to change multiple things and nothing's helped it the past 2 years. The car comes up with no codes and no obvious signs of what the issue is..I really hope someone has an idea to get it fixed I haven't tried yet. I really love the car and want to look after it.

 

[CamryFL]

When it is hunting - is that at idle, or when under acceleration ?

 

[Jess8591]

Its on both idle and acceleration

 

[Jess8591]

When it is hunting - is that at idle, or when under acceleration ?

Its on both idle and acceleration

 

[Strega315]

When does it have the drivability issues? When the outside air temperature is hot, warm, cold or all temperatures? Does it do this right when you first start it up or after you’ve been driving the car at normal operating temperatures? Have you tried pulling codes when it is actually acting up? And list the parts that you have had replaced by your mechanic(s) or yourself.

 

[CamryFL]

+1 w/ Strega, some additional info would be helpful - is it dependent on outside temp., the weather (sunny, humid, raining, etc.), does it occur when the vehicle is started cold, during warming up, when at operating temp., (or all times), does your Camry have an OBDII diagnostic port to hookup an OBDII scanner to see codes / sensor values.

 

[Toyota_JP]

The intermittent problems are the WORST!
Interesting it doesn't throw any codes and maybe that will help locate the problem. Pay more attention to some folks here who are much more the experts than I am but I'm kind of with Strega315 in looking at some environmental conditions that may be associated with the problem. Humidity and temperature may aggravate electrical parts that are borderline but still working. Maybe the ECU has a failing component that acts up when the car interior is hot. cold. or more humid than usual....maybe a small water leak in the AC evap line or even the heater core might elevate the humidity...aside from daily or seasonal humidity changes. Also wonder if you have a coil that goes intermittent during certain conditions....hot and humid weather perhaps. Again, these are just wild guesses based on very little information thus far to spawn some discussion that might identify your issue.

Possibly with exception of some failing ECU component, I would expect you to get a misfire code with a failing coil....but I don't know the error threshold required to initiate a code. If you haven't checked, look to see if there are any pending codes.

 

[1990Toyota]

My guess is that whatever is happening is happening in closed loop when you reach operating temperature. Whatever it is, is sending a sometimes-inaccurate reading to the ECM yet the ECM thinks it is correct as it is in "parameters" / scope for the ECM and it just thinks the outside conditions are being compensated for so its not settign a light........ and just pouring more fuel in then what's necessary...


I came across a car like this and it was the coolant temp sensor. it was telling he ECM to dump excess fuel at random times which caused the car to run similar to what you describe, yet it would not turn a check engine light on as the ecm though it was NEGATIVE 90 degrees etc.. .

Coolant temp sensor is a relatively cheap and easy fix. If its not that Id look at the MAF and the o2 sensor although
the best thing to do would be to get one of those little hand-held deals that plugs into the OBD2 port and reads live streaming data that the ECM sees. I use a cheap little$80 BOSCH 1000??? reader I got from Oreillys years ago and its been ridiculously helpful..its not as powerful as those alltell / Snap On deals, but for the price...

This will be hard to narrow down without some kind of scan tool... the best thing you can do is just park it when it acts weir and disconnect things that the computer will compensate for without the components readings like the MAF, o2 / CTS and see if the problem smooths out... in which case you can narrow down what it is and isn't.

 

[Strega315]

+1/ 1990Toyota - the ECT sensor was my first thought as well, and with it being an intermittent problem I was further boring down to the ECT Connector/wiring harness, as the wiring becomes somewhat brittle after 20-25 years and is subject to intermittent movement as the car is driven. I suggest OP manipulate the ECT sensor connector wiring harness gently while the engine is running at normal operating temperature to see if symptoms change as quick down & dirty troubleshooting step. The ECT sensor should throw a MIL code though, so OP's mileage may vary.

 

[93celicaconv]

I have a thought. Probably wrong. I had a 2003 Camry with the 1MZ-FE engine. Had almost 300,000 miles on it when I sold it - it still looked like it could get to 500,000 miles if the next owner took good care of it. Anyway, I had symptoms similar to the OP's, perhaps a bit milder, and episodes happened randomly. I found on some internet site that an EGR valve position sensor used on that engine sometimes develops a hysteresis that results in an inaccurate output of the sensor plunger (which is against the EGR valve) back to the ECU, which causes the ECU to open the EGR too far. I looked at the part for a 2000 Camry 1MZ-FE and for my 2003 Camry 1MZ-FE, and both engines use the same part number for this sensor (89455-33020). What I did was I went to a salvage yard and got a spare EGR valve position sensor, then swapped sensors on my engine. The problem was gone for many months. It did come back very mildly, so I swapped back to my original, and the problem was gone again - for many months. So I just kept a second EGR valve position sensor and swapped them whenever I felt the earl onset of these symptoms.

Don't know if this is the OP's possible solution, but maybe.

 

[Jess8591]

Thanks for your advice I'll try add as much info as I can and try reply to you
Car has 320,000ks
When car first started to hunt it was scanned 02 sensor code, fixed both sensors and rescanned, has no codes.
No engine light, no over heating, no smoke, no coolant problem. Changed gaskets because small amount of oil coming out the front and throttle body had a little oil inside which was odd but have cleaned and replaced no new leaks. No obvious problem with oil dosent use anymore then it should be and dosent drop puddle of oil underneath. Changed spark plugs, coil packs, vacuum hoses.
When it hunts, it doesn't matter what the weather is, time of day, how long the cars been running for ect it's completely random. AC on or off does not effect the problem. Car dosent stall, starts every time and can drive for hours or whatever with no engine light..smoke etc
EGR valve could be a possibility but I'd think from the hunting and the effect it's having on the engine I'd thought mafs would throw a code or be faulty, everything seems fine.

 

[Big D 66]

I just saw a video from one of the youtube Toyota mechanic guys a day or so ago where they found a bad wire on the ect sensor. Some older years had different sensors for the gauge and the computer, so the gauge would look fine even though the computer was getting an intermittent signal. When the wire would move a little, the connection was lost and it would go into "default" mode which was cold, so it would start dumping fuel in. Not saying that's it, but Strega315's suggestion is worth checking out, regardless of what your gauge says.

 

[Jess8591]

I just saw a video from one of the youtube Toyota mechanic guys a day or so ago where they found a bad wire on the ect sensor. Some older years had different sensors for the gauge and the computer, so the gauge would look fine even though the computer was getting an intermittent signal. When the wire would move a little, the connection was lost and it would go into "default" mode which was cold, so it would start dumping fuel in. Not saying that's it, but Strega315's suggestion is worth checking out, regardless of what your gauge says.

ECT sensor has been changed aswell- no change in the hunting. Both lines look fine on the sensor aswell, could it be a computer problem

I have a thought. Probably wrong. I had a 2003 Camry with the 1MZ-FE engine. Had almost 300,000 miles on it when I sold it - it still looked like it could get to 500,000 miles if the next owner took good care of it. Anyway, I had symptoms similar to the OP's, perhaps a bit milder, and episodes happened randomly. I found on some internet site that an EGR valve position sensor used on that engine sometimes develops a hysteresis that results in an inaccurate output of the sensor plunger (which is against the EGR valve) back to the ECU, which causes the ECU to open the EGR too far. I looked at the part for a 2000 Camry 1MZ-FE and for my 2003 Camry 1MZ-FE, and both engines use the same part number for this sensor (89455-33020). What I did was I went to a salvage yard and got a spare EGR valve position sensor, then swapped sensors on my engine. The problem was gone for many months. It did come back very mildly, so I swapped back to my original, and the problem was gone again - for many months. So I just kept a second EGR valve position sensor and swapped them whenever I felt the earl onset of these symptoms.

Don't know if this is the OP's possible solution, but maybe.

This engine 1mzfe seems to have a particular problem with sludge and airflow so I'm thinking of putting a catch-can instead of the EGR. Give it more airflow hopefully help with overall engine use. I do think this may be a problem it will have for a while, I have replaced EGR before and nothing changed. All leads look fine not worn either.

 

[shadako]

.... are you in qld? Anyways, sludge is over emphasized in these engines. as long as you do regular oil changes + clean or replace pcv, should be ok. recommend 10w 40 vs 5w 30 as getting leaks with 5w 30. First guess would be throttle body wire. Adjust or replace due to excess slack. Clean IACV + check corners of throttle butterfly as carbon is meant to get into there and keep it open. Cleaning out the pcv, breather hose + checking its operating correctly is important as well. Fair bit of slightly burned oil in my one at 240k kms.

 

[CamryFL]

When it hunts, it doesn't matter what the weather is, time of day, how long the cars been running for ect it's completely random

Has the fuel pump / fuel pressure been checked, as part of any prior diagnostic?

 

[DFBonnett]

Have you tested the throttle position sensor?

 

[1990Toyota]

id still look at the CTS, its not "a coolant problem" but the CTS sits in the coolant passage and tells the computer the temp of the motor etc. .and tells the computer how much fuel to dump into the engine.


Hearing your story though... Im personally leaning towards MAF or ECM now though.

Regarding the MAF....Heeres an old mechanic's tip... when it acts up, tap on the MAF with the back of a screwdriver lightly. See if it improves or gets worse and then you can see if it's a bad MAF

You can also try starting the car and unplugging the MAF and restarting and see if the issue goes away. if it runs better with the MAF disconnected then the MAF is usually bad. keep in mind this method will set a MAF code... but you can just clear the code later... Toyota MAFs are pretty good / pretty bullet proof though... but you may be the one who has a bad one.


it is possible the ECM is bad / stroking out during these times.......it does seem rather odd that its not throwing any codes during these "situations."


For the old GMs you could just throw in a spare ECM and change out the PROMS. But those were cheap and plentiful. You could grab a used one on ebay for kinda cheap and throw it in when it starts to act up. I can't recall if these are plug and play ECMS or if they need to be programmed though... if i recal lthey are plug and play as long as you get the correct one / they were before the era of VIN matching the ECM to a car. Verify that first though.

 

[cgravenor64]

My guess is that whatever is happening is happening in closed loop when you reach operating temperature. Whatever it is, is sending a sometimes-inaccurate reading to the ECM yet the ECM thinks it is correct as it is in "parameters" / scope for the ECM and it just thinks the outside conditions are being compensated for so its not settign a light........ and just pouring more fuel in then what's necessary...


I came across a car like this and it was the coolant temp sensor. it was telling he ECM to dump excess fuel at random times which caused the car to run similar to what you describe, yet it would not turn a check engine light on as the ecm though it was NEGATIVE 90 degrees etc.. .

Coolant temp sensor is a relatively cheap and easy fix. If its not that Id look at the MAF and the o2 sensor although
the best thing to do would be to get one of those little hand-held deals that plugs into the OBD2 port and reads live streaming data that the ECM sees. I use a cheap little$80 BOSCH 1000??? reader I got from Oreillys years ago and its been ridiculously helpful..its not as powerful as those alltell / Snap On deals, but for the price...

This will be hard to narrow down without some kind of scan tool... the best thing you can do is just park it when it acts weir and disconnect things that the computer will compensate for without the components readings like the MAF, o2 / CTS and see if the problem smooths out... in which case you can narrow down what it is and isn't.

I would read the coolant temp sensor, and the intake temp sensor

I have a 2000 Camry -V6 1mzfe engine
Owned this car just over two years, the problem with this car is for months it will drive great no problems at all and then suddenly it starts to hunt extremely bad and loses some power in throttle, revs out further really struggles and smells like it's over fueling. It does this for about 2 weeks off and on everytime I drive it then stops and drives great for months again and then it comes back and so on..been to many different mechanics and tried to change multiple things and nothing's helped it the past 2 years. The car comes up with no codes and no obvious signs of what the issue is..I really hope someone has an idea to get it fixed I haven't tried yet. I really love the car and want to look after it.

I would check the air intake temp sensor, I have seen those go wild, or never changes, so it thinks incoming air is either really hot will back of fuel, or really cold, and will add fuel, or may sit around 60 degress and never change, and the coolant temp sensor, not the coolant temp sender, I had one on a Lexus SC300, it would one minute be ok, and as the temperature increased, it would expand like it does, and short out, causing it to think it is -45 outside and just dump fuel, the other one I have seen, low coolant, make sure that system is full and no air, and that the thermostat is working properly, word of advise, as a level 3 Tech, I have found Toyota, Lexus, and Honda hate aftermarket parts, and I mean hate, they have caused me so much head ache.
you will need a good diagnostic tablet, or a friendly mechanic with one to get the true readings and to watch live data.

 

[Wheatwacked]

Load test the battery or try replacing it. an intermittant internal short would cause low voltage getting the ECM confused, but still have enough power to crank and start effortlessly. Low voltage will not set a code.

My 1999 S10 drove me nuts for two years with intermittant drivability. I replaced the fuel pump twice. Finally replaced the battery and never happened again. I got a battery load tester at Harbor Freight for $20.
Could be clogged injectors. No codes will be set and can be intermittant. The long term fuel trim will be about +20. A $10 bottle of Techron Fuel Injector Cleaner will fix that.
Fuel pressure regulator or its vaccuum hose cracked. Junk in the fuel tank clogging pick up screen? Go over all the sensor wiring and vaccuum lines. All it takes is a fingernail sized cut grounding out or leaking.
Loose air intake plenum allowing intermittant air to bypass the MAF?

I'm thinking of putting a catch-can instead of the EGR. Give it more airflow hopefully help with overall engine use.

DON'T. A catch can is to catch oil being sucked by the PCV valve. Sludge is caused by crankcase ventilation issues. It might help to replace the PCV valve and hose. That could be intermittantly sticking. My 69 Sprite came with a catch can before the PCV valve. EGR lowers cylinder wall temps to stop nitric oxide from forming and making our skys yellow.

 

[Scruffy J Scruffer's]

My Camry better not do this or I'm off to the car shop for 2 or 3 cans of electronics cleaner, Maf sensor and tunnel area would be repeatedly shot and checked for critters and spider webs. After a dual blasting all engine bay connectors with cleaner, shoot with compressed air.