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Honda accord-random deceleration while in motion

1999 Accord V6
Randomly decelerates while on the hwy. Pushing the gas peddle does not help. Thankfully hazard lights work.
Check engine light on but goes away on occasion.
Needs new engine mounts and O2 sensor according to diagnostics

A defective O2 sensor won’t cause this. The next time it does this watch the tachometer. If the tach acts goofy replace the ignition coil.


A faulty ignition switch is a possible, if all the guages go dead too that is a clue pointing to the ignition switch.

The '99 Accords are under a Recall for the ignition switches and you can have this done free of charge if the Recall has not been previously performed.

There are a number of things that could cause this problem but seeing as how the switch is potentially free you should take advantage of it.

So the tachometer does act funny all the time…but I assumed this was due to needing to replace the engine mounts. It almost feels like the car is unable to shift gears when I push the accelerator and the RPM will shoot up to 2 or 3 when trying to accelerate, even if I am going 40mph to 50mph. I try to be gentle with the gas peddle.

Thanks so much for your input friends! I will definitely look into the ignition switch ASAP!

If the tach is acting erratically, check for codes again and see if a P0725 code is stored. This indicates an Engine Speed Input Circuit Malfunction. The engine input speed is provided by a signal from the ignition coil to computer and the tachometer. If the signal to the tach causes the tach to act erratically that signal is also being seen by the computer. This erratic signal confuses the computer to where the computer doesn’t know when to shift the transmission and into what gear.