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While queuing to get into the McDonalds drivethrough recently I've noticed that my car vibrates quite a bit while idling in D. If I pop it out into neutral or park it goes away.

I found some old threads on the US version of this website where lots of people had this issue and never found a solution, even after changing the engine and transmission mounts.

Anyone else run into this?  The car is well serviced (probably over-serviced, I change the oil every 3000 miles or so) and had new plugs recently and transmission fluid about 20,000 miles ago.

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What is the idle speed when in D?

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27 minutes ago, m4rkw said:

While queuing to get into the McDonalds drivethrough recently I've noticed that my car vibrates quite a bit while idling in D. If I pop it out into neutral or park it goes away.

I found some old threads on the US version of this website where lots of people had this issue and never found a solution, even after changing the engine and transmission mounts.

Anyone else run into this?  The car is well serviced (probably over-serviced, I change the oil every 3000 miles or so) and had new plugs recently and transmission fluid about 20,000 miles ago.

Its probably your car shaking with the shame of it being forced to go to McDonald's 

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11 minutes ago, ColinBarber said:

What is the idle speed when in D?

About 600rpm. In neutral it's about 750.

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I guess I should try the cheap stuff first, spray clean the throttle body and maf sensor?

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3 minutes ago, m4rkw said:

I guess I should try the cheap stuff first, spray clean the throttle body and maf sensor?

Yes worth a go, and also check if it makes a difference if the AC is on or off.

It is possibly just because the idle is a little too low - it may be better when AC is on as the engine revs are normally increased to help with the increased load.

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6 minutes ago, ColinBarber said:

Yes worth a go, and also check if it makes a difference if the AC is on or off.

It is possibly just because the idle is a little too low - it may be better when AC is on as the engine revs are normally increased to help with the increased load.

I always have the AC on, unfortunately the vibration was pretty significant even with it on.

TBH I'm tempted to just ignore it and shift to N when idling for long periods.

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How much will it adjust fuel trim without setting a CEL? I'm wondering if it's worth checking the trim, could be leaning out due to a vacuum leak. It's never stalled though and the idle speed seems stable even though there's vibration.

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A reasonable amount. You are best to hook up diagnostic equipment to the OBBII port to see where the long term fuel trims are. As you say there could be a vacuum leak or an O2 sensor not working as well as it should.

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I've probably asked this before but the non-legit techstream cables make me nervous when a lexus ECU costs about £2 grand. Are any of these Bluetooth / iOS OBD2 adapter things capable of reading stuff like fuel trim on a toyota?

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16 minutes ago, m4rkw said:

I've probably asked this before but the non-legit techstream cables make me nervous when a lexus ECU costs about £2 grand. Are any of these bluetooth / iOS OBD2 adapter things capable of reading stuff like fuel trim on a toyota?

Yes they virtual all are able to do that - if they work at all then it should be able to read fuel trims. More expensive ones can read faster for better diagnosis of faults but you don't need this.

It is more around the software capabilities of the application you are using, some don't read the realtime data, only fault codes. E.g. the Carista app can only read error codes and set customisations, but their adapter + different software such as OBD Fusion can read realtime data such as fuel trims (https://www.obdsoftware.net/software/obdfusion)

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Thanks, my mechanic friend reckons its most likely the mounts so I'll probably take it in next week.

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The plot has thickened. I first noticed a faint rattle while queuing to get into McDonalds. This morning I reversed out of the driveway to go to the park without any noises. Then I replaced the air filter and since then in reverse gear there's a loud knocking sound from the engine bay. On investigation it's this big plastic "air resonator" which is adjacent to the air intake. What's really confusing is it's so close to the chassis that I can't see how it ever didn't knock. In reverse the airbox is shaking all over the place so I'm guessing mounts are still the root cause, but this thing seems way too close to the chassis. Hard plastic right next to metal, any vibration in the airbox and that's going to rattle like hell.

 

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Solved!

That’ll do until it goes into the garage. Hopefully it won’t catch fire before then.

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Very gentle load-braking. Pretty sure the mounts have failed.

 

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Hmm I dunno, maybe this is normal? Some people say it shouldn't move at all, some say a small bit of movement is ok. No idea really.

 

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Heh, more research and I've now realised one of the mounts is right there at the top and easy to see. Definitely shot to bits.

 

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Turns out I was wrong, the top mount is a bit worn but not in imminent need of replacement. The knocking was caused by the air resonator being mounted in the wrong position, now fixed by my local garage, and generally I was advised not to idle for long periods with the transmission in gear.

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