Mechanic help? preferably honda specialist?

(2010-05-28 00:46:21)

1. Josh Says: Ok, my 1987 honda prelude Si had a terrible idle problem, it was revving up and down which started lightly but eventually did it all the time. I had my friend replace my clutch and take a look at it so he hooked it up to a computer, which read it was the egr valve. He said nothin seemed wrong with it but he then tried unplugging the throttle position sensor which made it idle rough, but stopped the bouncing. Now im on a endless search for a throttle position sensor, but i was also told it was riveted into the throttle body and i would have to replace the whole thing... So i guess my question is am i really gonna have to replace the whole throttle body and is it safe to drive it with the TPS unplugged? I appreciate any feedback, im gettin fed up with this mess. thanks

2. honda guy Says: your problem isn't with the throttle position sensor; that is doing what it is supposed to do in reporting the position of the throttle plates which are moving because the idle bypass port for the idle air is plugged with carbon or the idle air control valve isn't working.

if you look inside the opening of the throttle body from the air filter side (air bellows removed) you should see a hole (port) on the inside wall about half way up. that is the passage for the idle air that bypasses the throttle plates and keeps the engine running at a steady speed. when that passage gets restricted by carbon (think of soot in a chimney) the air can't bypass the throttle plates and the engine starts "gasping" for air (think or sprinting for 100 yards at full speed then stopping). so when the engine is gasping it is pulling the throttle plates open and closed and the throttle position sensor sends a signal to the electronic control unit to adjust for that movement.

so to fix it, start with getting an aerosol can of carburetor cleaner (or throttle body cleaner) and spray it into the idle air bypass port. If you can find a pipe cleaner, you may want to use that as well once the carb cleaner has had a chance to work. if that doesn't fix the problem you will have to remvoe the idle air valve to clean it.

also, look for any signs of a vacuum leak such as a broken vacuum line on the intake manifold as that can cause the problem as well.

hope that helps

3. bill b Says: I have had this problem many times and as simple as it sounds try adjusting the ignition timing first i'll bet your going to find it's off a bit and this might just fix your problem also there is an air adjustment near the butterfly that might also give you the results your looking for. Plug the tps back in and try these two things.

4. alexander m Says: the TPS isnt rivited to the TB, its screwed on and you can unscew it. try adjusting that. you can also adjust the screw on your TB that adjusts idle RPMs, it might be a bit loose.
if your EGR valve is clogged or damaged, u should replace it.
my best advice though is give your engine a complete tune up if you havent in a while, check yoru belts, etc.