Hi, I recently replaced the front head gasket on my 2005 6mt TL, put everything back together and now my engine while in nuetral constantly revs itself from 1000-2000rpm. Every time it drops to 1000rpm it revs itself to 2000rpm and it goes through this constant loop, never stopping. Even while driving it doesn't matter which gear I'm in, if I let off the gas and have the rpms drop down to 1000rpm, it will shoot itself back up to 2000rpm and then drop again. It's like it is keeping itself from stalling, I've tried to stall it and it will just keep revving itself. Any ideas on what might be causing this?

 

Sounds like you have air in the cooling system.

 

Any idea on how to fix this?

 

Bleed the cooling system. There are posts here on the procedure as well as any number of YouTube videos on how to bleed the cooling system for J-Series Honda engines.

Keep us posted.

 

Air in the cooling system causing the engine to rev at idle? Never heard that one before.....I would assume with the description there is a vacuum leak or a failed sensor somewhere doing wonky things.

 

On Honda J-Series engines, if there is air in the cooling system it definitely causes the engine to oscillate between low and high RPMs; this happened to my old J30A1 equipped Accord on several occasions. In the case of that car, so many systems were failing almost at the same time due to corrosion, it was crazy, however, whenever the engine started revving up and down, I always knew it was time for more coolant.

 

So went back to the car today checked over all the hoses and everything is plugged in tight, but now the battery is dead, went to jump start it and now instead of the car revving itself, it just has a high pitch scream coming from the engine bay?