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2002 Honda Accord LE with automatic transmission shakes like crazy when it idles

We took our car in for a regular oil change and to get the 60K belt work done. While in the car they discovered that the transmission was slipping and that we were missing one of the motor mounts. They did the belt work and the oil change and then put some fluid in our car hoping that would buy us some time with our transmission. To save us time and money they said we could wait a little while on the motor mount. When I drove it home the whole car shifted and shook whenever we would come to a stop and then it would shake while idling. I called our mechanic back and they said to bring it in and that fixing the rear motor mount should take care of the problem. While back at the mechanic for the motor mount they discovered that the transmission additive had not worked and we needed a new one. We bought a rebuilt one and now we are still left with a car that shakes when we are idling. We have had the car in two or three times after the transmission was put in for them to try and fix the issue. They have done everything short of removing the engine without any luck. Just to be sure they covered every possible angle, they just gave us new spark plugs, ignition wires, distributor rotor, distributor cap and PCV valve, but it didn’t seem to do anything. The car shakes the most while idling in Drive, somewhat less in Park, somewhat less than that in Neutral and not at all in Reverse. The shaking gets even stronger if the A/C or defroster is turned on. It seems to be even worse when stopped on a downward slope. It has been several months of this and the shaking is incredibly annoying. Is there anything else our mechanic could look into? Thanks in advance!

Anytime an engine performance problem exists a compression test should be run to weed out any possibility of a mechanical fault in the engine.
They changed the spark plugs (that’s generally everyone’s first step) so why on Earth would they not kill this bird while they’re at it?

There are other things it could be (vacuum leak, etc) but I’d clear up the possibility of any engine problems with a compression test.
Hopefully it’s not a tight valve due to neglected valve lash inspections/adjustments.

Hopefully they used the correct Honda fluid in the transmission. Some Honda’s are really picky, and the wrong fluid can cause all sorts of weird things to happen, including killing a transmission.

In addition to the timing belt, there is a belt for the balance shafts. If the balance shafts are not aligned properly when the belt is put back on after the timing belt is replaced, you engine is going to shake violently.

It is actually shaking throughout the rpm range but the vibrations increase in frequency and decrease in amplitude as rpm increases.

Did you get this done at a dealer? If not, did your mechanic ever attend training on Honda’s? This is a tricky engine to work on, especially aligning the rear balance shaft.

How did they determine that the transmission was slipping by doing an oil change? And a missing motor mount, was this car in a serious wreck at some time? BTW, your model should be LX, not LE.

I sure wonder why a 60k miles Honda suffered a failed transmission already and why in the world a motor mount would be “missing”.

If the vibration only surfaced after timing belt work then I would agree it could be a belt timing issue or possibly a vacuum problem. This brings into the credibility discussion a shop that would be confronted with a vibration problem which only surfaced after a belt change and their throwing a number of parts at it.

To answer some of the questions:

  • We didn’t get it done at a dealer, but our local mechanics have said that if all else fails they’ll take it to a dealer and reimburse us for the difference. They’ve been very helpful throughout this process, and we have never had any major issues with their work before this one issue.
  • Yep, it’s LX. I was trying to remember what the model between DX and EX was, and I knew there was an L in it. Sorry about that.
  • This was the 60,000 mile inspection, not just an oil change and replacement of the timing belt. I also misspoke concerning the rear motor mount: they replaced it because it was worn, not because it was missing. (That’ll teach me to post this stuff on four hours’ sleep.)
  • One of the mechanics did attend the certification training to “officially” work on Hondas. To my knowledge, they haven’t gone inside the engine to mess with anything yet, although they did have to remove it for the mount work.
  • We bought the car used at CarMax in Florida, so while we don’t know the full history of the car, we do know that it hasn’t been in any major wrecks. CarMax doesn’t accept any car that has had to have major body work or repairs.

Thanks for the feedback so far. I’m going to check with my mechanics to see if they ran a compression test, made valve lash adjustments, and checked the belt for the balance shafts (although I’m pretty sure that the mechanic showed me that belt the last time; I know enough to know it wasn’t the timing belt. It seemed to be working fine with no major shaking or irregularity.) I’ll update the post once I have more information from them and have access to the repair invoices in the glove box.