Rough running all speeds 2002 V6 LE 1MZ-FE

[mxsmith]

I have 144,000 miles on my V6. Just started to notice that the car is surging/hesitating at just about all speeds. It appears to idle fine and if you raise the RPM in neutral I can't detect a problem. If you place the trans in drive, apply the brake and raise the RPM to 1000 to 1500 the engine's RPM varies slightly and regularly, it not steady like all of my other cars. When you are at highway speeds you can feel the car slightly buck, if you take it out of overdrive it is more detectable due to higher RPM. I do not notice the problem when the engine is cold.

I have a hand-held scanner and I see no codes and there is no CEL illuminated. I changed the plugs with OEM plugs at 90,000 miles when I changed the timing belt. Changed the air filter probably 10,000 miles ago. Just cleaned the MAF sensor (after the problem started), no change. Took it to the dealer. They discovered broken motor mounts which I kind of suspected I had, but I didn't feel the symptom were mount related. They said that I was feeling torque converter lock-up. I told them that the range of speeds and gears that the problem presented itself that it was unlikely lock-up.

Alldata suggests that it is a fuel problem and Toyota has some TSB's for drivability. I'm discounting the TSB's because this just started recently. Any hints as to where to try first? EGR, fuel regulator, fuel pulsation damper, injectors, spark plug coil packs, ..... It gets too expensive to just remove and replace the sensors that deal with the fuels system. I have plenty of tools plus a volt-ohm meter and a fuel pressure gauge.

07/21/2009
While I was at work I added Seafoam to the gas, tank was half full.

On my way home from work I disconnected the EGR Position Sensor connector and the symptoms disappeared and the expected CEL illuminated. When I arrived home I went on Alldata and looked for an EGR system test. I found two, one for the position sensor and one for the EGR temperature sensor.

I had to run out to Sears to pickup a vacuum pump. I performed the tests below up to the point that I needed the pump. I also removed, inspected and reinstalled the EGR Position Sensor before I left for Sears. I did not notice the symptoms on the trip about 14 miles round trip. I'll see if I still have the problem on my way to work tomorrow.

Performed the on-vehicle inspection as listed on Alldata
EGR Position Sensor resistance: 2.6 ohms, in spec
EGR Position Sensor power: 5.0v, in spec
EGR Position Sensor output with no vacuum applied: 1.0v, in spec
EGR Position Sensor output with 5.1 in Hg vacuum applied: 4.0v, in spec

07/22/2009
Problem seems to have gone away, no bucking or hesitation. Maybe the connector contacts were dirty on the position sensor. Will update if the symptoms return.

09/07/2009
Noticed that I am getting 2 miles per gallon more than before I found the problem.

[X35]

I have a 2003 Camry V6. I HAD the same hesitation / stumble. My problem could be felt mainly with very light throttle going down a slight hill or coasting with slight throttle on level ground. Also driving real slow in a parking lot it would really surge.

I read your post so I thought I would give it a shot.

I removed the EGR sensor, moved the plunger in and out a few times, tapped on the EGR inside where the plunger rests and then put it back together.

The problem is GONE.

I even had my wife drive it to make sure I wasn't dreaming.

Will see if it comes back tomorrow on the way to work.

Thanks for posting. I have been looking for a solution for a long time and this really helped me out.

By the way, I read a stuck EGR could cause the hesitation, so EGR or sensor stuck may have caused it and / or the dirty connector.

[xpeed]

Hmmm, if it's not the mounts, try to check if your engine is balanced well also if the there's any loose mounts, have those checked as well.

[mxsmith]

Glad I could help.

If my EGR was stuck, it's not anymore. I connected a voltmeter to the ERG position sensor while it was connected to the EGR valve and took the car for a ride. I could see the output vary according to engine RPM/load.

Still running smooth.

[George Krug]

I hope you fellows have found the solution that three Toyota dealers could not (or would not). I have an '02 Camry v6 with 85,000 miles. Several months ago I noticed the exact problem described by X35 and mxsmith. Just a few questions.....when I remove the EGR position sensor what will I find? I hope it's not a bunch of springs and clips jumping out. What should I use to clean the sensor's plug? Electrical contact cleaner? And is there a way to clean the EGR plunger?

[mxsmith]

If you remove the EGR sensor there will be nothing jumping out at you unless something broke. The sensor is a self-contained unit. The sensor plunger should remain in the sensor. I did not use any cleaner on the plug or the EGR valve. Just unplugged and replugged the sensor into the socket several times.

To really checkout the system you will need a volt-ohm meter and a vacuum pump. If the sensor is bad you can buy it separately, you don't need the entire EGR valve assembly.

[mxsmith]

My dealer didn't find the problem either. They replaced the engine mounts and I guess were a little over-confident that they fixed the problem that they didn't drive test the car after the "repair".

[George Krug]

This morning I unplugged and removed the sensor, worked the plunger up and down for half a minute. Put it back on and plugged and unplugged the connector several times. The wife and I went for a 120 mile ride (city and country, stop lights and hills) so far the hesitation, bucking is gone. I'm glad I found this site, I've been to several Toyota dealers who never heard of the problem but they were more than willing to take a "stab at it"
Thanks for the help.

[X35]

I would say that rules out a stuck EGR. I am thinking removing the sensor has very little affect on the ERG valve itself.

To determine if it is the plug or the sensor, the next person that tries this can just unplug and plug back in the sensor a few times and see if it works on a test drive. If not remove the sensor and try the plunger in and out a few times, then, post the result.

I have driven about 800 miles and the problem has not come back.

My plug looked pretty clean so I am thinking something is going on inside the sensor. Hopefully somebody else can confirm sensor vs plug then post the result.

[George Krug]

the sensor and plug are so easy to get to, it's worth the try. I did notice when I removed the three tiny nuts holding the sensor on, it just lifted off. After working the plunger and reinstalling the sensor there was a slight upward tension. I had to hold it down with my finger just to get the nuts started.
The male and female parts of the plug looked clean, like brand new. The wife is going on a 700 mile round trip this weekend in the Camry. I'll post when she returns.

[X35]

I am adding some keywords so others may find this easier on google.
When I was looking for help on the internet, I found many sites with the same problem but no solution.

02 03 04 05 06
2002 2003 2004 2005 2006
V6
1mZ-FE
Toyota Camry
Stumbling, Hesitation, surging, down hill, downhill, flat ground, coasting, light throttle, low throttle, running rough, sluggishness, bucking, engine, vibration.

[George Krug]

With those key words I would have found this site a few months ago. It would have saved me a few hundred bucks that I had to fork over to the so called "technicians" at three different Toyota dealers.

[mxsmith]

This problem was driving me nuts too. I was reading up on what could cause an engine to run rough at other than idle. The EGR system was one of the items; fuel pressure, spark plugs, vacuum leaks, etc were also on the list. The cheapest, fastest test was to unplug the EGR sensor connector or to pull the vacuum line. I chose the sensor.

If you want to replace the sensor it costs about $35-$40. If you need a new valve it will come with a new sensor and a big price tag. I haven't seen any offered without a sensor.

[mxsmith]

My plug looked clean also. The sensor plunger moved freely when removed from the valve assembly. I agree it would be nice to know if it was just the connector or the plunger workout. A little info in my original post is that I removed the connector and drove the car a few miles without the symptoms. So my vote is on the connector and possible oxidation.

Electrical contacts can form a very thin layer of oxidation that we can't see, so a visual inspection would only detect corrosion. There is a spray called Deoxit DN5 that worked wonders on my handheld Garmin GPS, but I did not want to tell someone to spray the stuff on their car's electrical system especially when a few plug/unplug cycles on the connector does the same thing.

[George Krug]

The sensor's plug and connector also looked clean on mine but I plugged it in and unplugged it several times anyway. Sensor's plunger had a slight resistance when I first pushed it in but it worked free afterword. Just wondered if this is a common problem where people are taking ther cars to the dealer to be fixed and leaving with a $600 bill