Hi all,
I was hoping I could tap your guys' knowledge a little bit. My friend owns a 2001 Honda Prelude SH with ~55,000 miles on it. Just recently he has been experiencing lower than usual RPMs when idling. They usually sat around 700-900, now they are close to 500. Also, i believe he said that when he runs at 35 mph, his car would be around 3K rpms, but now, its lower at 2500 RPM (i forget what gear he told me he noticed this in..)

We noticed one more thing. In the vicinity of the intake air manifold, he has this whining, scratchy sound that comes in and out. It is heard predominately when he accelerates, and as he lets off of the gas, it remains for some time (0-throttle) at which point it comes in and out. Its hard to describe the sounds. Its scartchy, while being a bit whiny and wheezy. Almost like if a injector is having trouble spraying? im not entirely sure.

He took it to a mechanic friend of his, and he could not figure it out. Could it be maybe misfiring? (it should throw a code...but he has no codes). I was thinking maybe a valve adjustment is required? Im not too sure and was hoping you all could help shed some light on this issue. Thanks!!!

 

check the engine compression?

Has he been racing it? driving it hard? Possible he fried a Piston ring.

 

No, he just uses it as a daily driver around school. He has never raced it, although he is the second owner on the car. He got the car back around 2002 with about 14-15K miles on it.

But....To go along with your theory....
One thing he told me was that he car burns oil, and every month or so he would add some oil (like 1/2 qt or less). This time around he came home, checked, and saw that it was well below the lower "L" indicator and he neglected looking after the car for a bit...

Thanks Sarlacc...ill let him know to get a compression test done

 

RPM shouldnt/cant be any lower while moving. Thats all a ratio of gearing and cant change (unless its a auto). Has said friend tried to do any shade tree mechanic work himself and adjusted things that he shouldnt have?

 

Check the PCV

 

Good thing to check for the oil consumption

 

thanks Ken1997TL for the suggestion. Ill mention it to him.

Fsttyms1 - No, he really hasnt done any sort of do it yourself work or adjustments by himself. He said ever since he got the car, he has been burning oil, but this time around he completely forgot to do his routine checks on the car. When he did do it, he saw he had burned a lot of oil. I asked him just a few moments ago how much he actually added to get the level back up, but he has yet to respond just yet. On friday, when i spoke with him, he stated that "it was a lot...more than usual".

The only DIY item he has done is spark plugs and wires, where we swapped out the old NGKs for new NGK iridiums. The wires were of OEM quality (i forgot what brand we specifically used..it was about 2 years ago we did this and it was not a cheap knock off, nor was it performance).

 

Vacuum leak?

Check all hoses/clamps/connections where fuel, coolant and air are transported

 

+1, my buddy had the same problem with the same car

 

Thanks I Go to Costco and Crazyasiantl. I just sent him an email summarizing the suggestions on this thread.

 

Just as an update.
That mysterious scratchy, wheezing, whiny sound is now gone. In the very same vicinity of the Intake air manifold lies the oil filter. He changed out the oil filter yesterday, and now that sound is gone.

 

he hadnt tightened the oil filter enough and was leaking more oil than usual as for the rpm thing, he may just have been paranoid.