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#1 (permalink) Old 01-13-2013, 11:05 PM
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Rough Idle under load?

Hey,

Drove the RAV4 as I dropped my 4Runner off at the dealership for the transmission service. I noticed the rav has a rough idle when in drive (such as stopped at a light). When I put it in park, it is smooth. It never did this before, so I'm not sure what it could be. Spark plugs perhaps? Spark plugs were replaced at the dealer at 102,500 miles. It has 146,127 now. Due for an oil change in a thousand miles. Any advice would be appreciated, thanks in advance.

2005 Toyota RAV4 4WD

2006 Toyota 4Runner SR5 V8 4X4-current tuck

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#2 (permalink) Old 01-14-2013, 03:13 AM
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I would suspect that your throttle body is a bit gummed up with carbon. As you put the car on load at idle the car has to increase the amount of fuel/air very slightly if something is sticking slightly this can cause a rough idle.
At your mileage its definitely worth investigating how to clean your throttle body.

I gave mine a clean at 50000 miles after rough idle problems. My engine was a European 2l so location and cleaning details are different to yours. Before cleaning the car would be jerky if I tried to creep along in idle, after cleaning its was dead smooth.
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#3 (permalink) Old 08-21-2013, 10:59 AM
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This is more of a generic reply to the issue of rough idle with the caveat that it may not apply in all situations. Here is my experience. Recently I had some major warranty work performed on my 2008 Rav4 Transaxle. The work required (evidently) that the batter be disconnected. After picking up the car, I noticed immediately a very rough idle especially when coming to a stop. The same had occurred when I had a trailer hitch added by U Haul and again, rough idle. Come to find out whenever the battery is disconnected, it sends the computer into orbit and it will take approximately 50 miles of regular driving for the computer to basically reboot and get back to default settings for idle etc. This point was reinforced when I took my wife's Forester in for the annual inspection sticker. A light had been left on and the battery died. I recharged the battery but the inspection could not proceed until the car again had been driven for 50 + miles. Ahhh, technology. Sometimes good, sometimes not so good. I hope this is helpful.
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#4 (permalink) Old 08-21-2013, 11:04 AM
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Originally Posted by procket52 View Post
This is more of a generic reply to the issue of rough idle with the caveat that it may not apply in all situations. Here is my experience. Recently I had some major warranty work performed on my 2008 Rav4 Transaxle. The work required (evidently) that the batter be disconnected. After picking up the car, I noticed immediately a very rough idle especially when coming to a stop. The same had occurred when I had a trailer hitch added by U Haul and again, rough idle. Come to find out whenever the battery is disconnected, it sends the computer into orbit and it will take approximately 50 miles of regular driving for the computer to basically reboot and get back to default settings for idle etc. This point was reinforced when I took my wife's Forester in for the annual inspection sticker. A light had been left on and the battery died. I recharged the battery but the inspection could not proceed until the car again had been driven for 50 + miles. Ahhh, technology. Sometimes good, sometimes not so good. I hope this is helpful.
Thanks for the input, this is not the case in my situation though. My 4Runner transmission does this, and has to relearn shift points once the ECU is reset. This differs from person to person generally because of different driving styles. I rarely get a chance to drive the RAV4 anymore because it's my sister's car now, but I noticed it's more of a noise than a vibration. I'm gonna put it in gear and have someone step on the brakes and I'll look in the engine bay to see if anything is loose.

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#5 (permalink) Old 08-22-2013, 12:40 AM
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Is the tach needle jumping around when at the stoplight in gear?
If so there could be a slight vacuum leak. So check all hose end for cracks or splits.
Also, check the molded duct between the throttle body itself and the intake manifold. They can crack with age and this will allow unmetered air in. Causing it to run lean. Too much air and the computer will cut back on the gas. It will stumble and then computer will respond with giving more gas, causing this uneven idle.
I would remove and clean the throttle body thoroughly as well as the MAF. Use the correct cleaner for each. Check the air filter too.
If you have a code reader such as Actron you can plug it in and take some data snapshots while driving to see what is happening.
Look at the short term and long term fuel trim values...If they are 0-8 that's good. Higher values mean an issue and it can be determined with some testing if a fuel starvation issue or vacuum leak.
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#6 (permalink) Old 08-22-2013, 12:44 AM
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Originally Posted by rcrahn View Post
Is the tach needle jumping around when at the stoplight in gear?
If so there could be a slight vacuum leak. So check all hose end for cracks or splits.
Also, check the molded duct between the throttle body itself and the intake manifold. They can crack with age and this will allow unmetered air in. Causing it to run lean. Too much air and the computer will cut back on the gas. It will stumble and then computer will respond with giving more gas, causing this uneven idle.
I would remove and clean the throttle body thoroughly as well as the MAF. Use the correct cleaner for each. Check the air filter too.
If you have a code reader such as Actron you can plug it in and take some data snapshots while driving to see what is happening.
Look at the short term and long term fuel trim values...If they are 0-8 that's good. Higher values mean an issue and it can be determined with some testing if a fuel starvation issue or vacuum leak.
Just replaced the air filter today actually. As mentioned, the "roughness" is mostly audible and sounds like something is loose. I don't actually feel vibration in relation to the noise. The tach needle stays consistent and the ride is smooth otherwise. I have never removed the throttle body on this car, is it easy to access? A quick look in the engine bay before made it looked like it was a bit out of the way. Thanks

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