I've owned my 95 prelude vtec 5 speed for 1 year. In the past 3 - 4 months, I've noticed my RPM has decreased when at my usual cruising speed. At 80mph, my RPM is at approx. 3000 (whereas it used to be a normal 3500, easy). Even pushing the speed limit to 90+ mph only increases my top RPM to barely 3300? I can't reach 4000 - 5000 RPM without feeling like I'm really "pushing" my engine to its limits...! My car "feels" normal -- no pinging, knocking, tranny feels smooth and by all other interpretation, my engine feels "strong". I just don't understand why the sudden loss of power?
even out of 1st gear, i can't rev my car past 3000 RPM. I usually go to 2800-2900 RPM before having to shift to 2nd gear... and every gear is the same -- my RPM does not spike past 3000 unless I press the pedal to the floor (which I am reluctanct to do, since I do not wish to stress the car; plus it used to drive normally before).

I've taken it to a Honda dealership where they ran diagnostics and they told me the computer chip did not return any errors with the car. They did find a crack in my header.

In the past month - I've replaced my cracked exhaust manifold. It did not increase my RPM. I also replaced my catalytic converter (it wasn't clogged like I expected, but I put in a new one anyway hoping it would help). Nope, it didn't help. I've even replaced the clutch (which just happened to go out). That didn't improve the RPM problem either...

Another weird thing is: about 2 months ago (before i fixed anything), I was driving to work and the problem miraculously CORRECTED itself! For my entire 15 minute drive to work that morning, my RPM was back to normal -- i could accelerate quick, punch my gas and see my RPM needle easily spike past 3000 - 4000, EASY. Then when I hopped back into my car later during my lunchbreak, it went back to being all f*cked up again! It's never improved since... what' sup wit dat?? I'm so confused... My resting (idle) RPM also seems a bit high (at 1500). It used to be 500 or so before all this began...

What could be the problem? Is it the O2 sensor? Is it my aftermarket cold air intake? my timing belt? I don't know where to look next -- running out of patience and money!

it says I CAN'T POST MORE THAN 5 MSG PER 24hr period??? how do i change my member settings? do i have to pay or something? i'm getting helpful IM's and replies... unfortunately, I'm unable to respond??!

also - what are the known symptoms of an old timing belt? could i possibly be a case study? (i've yet replaced mine in the year i've had it. it's got 150k miles on it)



Modified by pkprelude at 4:04 PM 5/8/2003

 

I'd change your distributor cap and rotor, your plug wires, and your spark plugs first unless you have done them very recently. Then I would look into the O2 sensor, but that should be something that would show up on your computer if it was malfunctioning. Also, check your timing.

 

have the dealer or yourself connect a tach to the blue tach test wire coming off the distributor and verify that yours is working correctly. Mine in my swapped hatch seems off to 70mph with a b16a2 stock gearing should be 4k and in mine it is not (it was in my si but not in the hatch i swaped it into after i totalled the si)
either speedo or tach is off in the hatch i am guessing....

 

This has to be an innacurate tach or an innacurate speedo. With a manual transmission there's no way for the engine to be turning slower than it used to, at the same road speed. Bad plugs, wires, cap, rotor, all that stuff will cause your engine to lose power. But it CAN'T give your transmission a different gear ratio.

For a really easy test, get a friend's car, (4-cyl) and hold both cars at the same indicated rpm. They should both sound at the same pitch, as if you're listening to a musical note.

Better yet, find a piano. (Don't laugh so hard.) Your 4-cyl engine makes 2 exhaust pulses every revolution, so at 3300 rpm that's 110 Hz. This is 2 octaves below A(440).