prelude won't rev past 6500 rpm after spark plug change
 

Anyone encountered this before? The car is a '99 honda prelude.
I just changed my spark plugs (and topped up the engine oil a bit at the same time). Now the revs are being limited to 6500. No check engine light. I tried putting the old plugs back in, and still have the problem. Also tried torquing the plugs in a bit more (was using 13 ft-lbs as per manual), but didn't help. Any ideas? Just coincidence that this happened now?

wierd sounds like its in limp mode.

couple of things here. scan the car for codes regardless (they might not set a MIL but there can still be pending codes in the computer)

make sure the car is at operating temperature.

if that doesn't work. check the vtec solenoid and clean the screen (it could be clogged).

and if thats fine. disconnect the battery and leave it for 30 seconds and then connect it again (to clear the ECU of its memory).

but if its stopped at 6500. the ECU is trying to tell you something is wrong. most likely a sensor of some sort isn't reading properly preventing you from taking the car into more dangerous engine speeds.

reset ecu, see if that does anything.

Thanks, guys. I did try disconnecting the battery so far. Didn't make a difference, or maybe I needed to drive around for a while before it changed. I'll have to try again and see.

Here's more info:
It used to rev past 6500 in neutral no prob. This is also happening in 1st and second gear too (haven't tried in the other gears for safety reasons).
The car is completely stock under the hood.

A friend at a honda dealership says the system might not be used to the bigger spark with the new plugs, and it might be limiting because the EGR valve has carbon buildup (it's never been cleaned or changed on my car, and this is the first time I'm changing the sparks). Supposedly there was a service bulletin about this which he's trying to find.
That sound right to anyone? Thanks for the suggestions.

Wow. you're posting this everywhere... Honda-tech, here, VPC... damn... it cant be that bad. Its probably just one of your plugs. swap your old plugs back and see if it still does it. Are the plugs gapped properly?

Is there a difference in acceleration after the change? and is the rev limiter going off?

double check the plugs, might be improper installation.