2003 honda odyssey idle

I have a problem with my 2003 Honda Odyssey engine idling (is that the right term?)when it is in park or driving at slow speeds like when I’m in a parking lot. Instead of staying at a steady hum, it constantly drops down and comes back up. We brought it in to a transmission repair shop and they said they may have to keep it for 4-5 days to figure out the problem and that with parts and labor it could cost anywhere from $800 or more. Is this answer as vague as I think it is? Is there a likely solution to this problem or will they really have to spend all that time looking for the problem?



Thanks,

Steve

Out of curiosity why a transmission shop? I would be inclined in this case if not other trusted mechanic use the dealer for diagnosis if not full repair. $800 number is completely pulled from the air.

What makes you think you have a transmission problem?

A disconnected or leaking vacuum hose could cause a fluctuating idle, as can many other things. I don’t think the transmission is the problem.

Has the CEL (Check Engine Light) come on? Even if it has not, it might be a good idea to see if there are any stored error codes in the computer. They would likely be a big help in figuring out what the problem may be.

We originally brought it in to a transmission shop because the green light indicating the car is in drive was blinking. We talked to someone at the dealership and they said that it indicated a transmission problem. (Unfortunately, we have moved since we bought the van and are not near a Honda dealer) This transmission shop said it was 1 or 2 faulty sensors and would cost $300 to fix. We thought it might be just a cosmetic problem so we didn’t have it fixed and now we have the fluctuating idle a month later. We took it back there because we thought the problem was linked to the sensor problem. They replaced the air control motor but that was not the problem.