89 Prelude with some questions...idle, exhaust, battery light

Hi

I have an 89' Honda prelude with 97000mi on it. The thing is mint, perfect interior, perfect exterior. The timing belt went on the previous owner, so the upper half of the engine has been rebuilt, valves, seals… it starts in a second. I have a couple questions though...

When I first start the car it idles at 1500- 2000 rpms. After about 4 minutes the idle will go down to about 700rpms, a little more normal...is there a way to fix this high idle...maybe ignition timing, or maybe a vacuum leak (I don't hear anything though) I wouldn’t mind it, but when I shift from park to drive it catches hard because of the high idle.

After the car warms up it gets an exhaust rattle that seems to be coming from around the cat. The rattle seems like the exhaust is hitting the floorboards. When I take a left hand turn the rattle goes away...when I take a right hand turn the rattle comes back, even stronger. I figure that the exhaust is not centered and that's why it's hitting, but the only thing that confuses me is that it doesn't happen when the car is cold. It takes a least 15min from start for it to happen. Any guesses? I checked underneath the car and there is nothing loose, everything seems solid.

One more question...the person who owned the car before e just had installed a new power steering hose because the old one was spraying fluid all over the engine. So...the first thing I did when I got the car was wash the engine at the car wash (high pressure). When I left the car idled really bad... I figured I got the distributor wet...it dried up and now it runs fine, but 2 days later I started it and the check battery light went on. I know it’s not the battery or the alternator...both were just replaced and the battery still holds a full charge. I checked the ecu and I got trouble code 15...ignition output signal. I have no idea what this means. The car still ran fine, so I unplugged the battery to reset the ecu and see if the code still comes up and it didn't, but the battery light is still on in the dash. I have no clue what to do.

Any help to these questions would be greatly appreciated,

Thanks

Tim

If you have the carburated engine for the Prelude, there is a very simple solution that can be done. Fuel injected engines that have rough idle are tougher to diagnose and fix; because there is a variety of things that can be wrong.

However, in your case, I believe that is normal. My dad's 87 Accord also starts off in higher RPM's and falls off when the car is warm.

Check your compression, one of your spark plugs/wires may not be delivering a spark.

TCHach11, a couple of possibilities here. I have an 88 Lude and I just finished going over every wire in the system. There may be a short in the wire harness that goes from the Alt. to the battery that was moved or "ungreased" when you pressure washed the engine. Water in the wire harness could be the dielectric causing the short...
Idle issue... I just replaced the Bypass control solenoid valve for a stall issue after high speed highway runs, and this is for you... Between the throttle body plume and the fir ewall is the high speed idle control valve. Simple check to see if it is working... remove top cover, (two screws in top), start engine ...cold... Stick your finger in... vacuum?... if yes, good. when the car warms up, the valve should close completely. mine was all gooped up. I removed it... three bolts and the two small coolant lines at bottom. I removed the bowl from the bottom and cleaned it all out, a shot of WD-40 in the valve body, hooked it back up and car runs great... the idle WILL be high during warm up. if you can let it warm up for about 5 minutes before you leave, you should be able to tap on the accelerator pedal and the idle should dropat least a few hundred RPM. As for the exhaust... our cars must be related,,, my exhaust rattles as the rpms pass through 2k before I shift into the next gear. Thought it was the exh. man. heat shield, mesh over premuffler... I let it go... Hope this helps.

TCHach11, a couple of possibilities here. I have an 88 Lude and I just finished going over every wire in the system. There may be a short in the wire harness that goes from the Alt. to the battery that was moved or "ungreased" when you pressure washed the engine. Water in the wire harness could be the dielectric causing the short...
Idle issue... I just replaced the Bypass control solenoid valve for a stall issue after high speed highway runs, and this is for you... Between the throttle body plume and the fir ewall is the high speed idle control valve. Simple check to see if it is working... remove top cover, (two screws in top), start engine ...cold... Stick your finger in... vacuum?... if yes, good. when the car warms up, the valve should close completely. mine was all gooped up. I removed it... three bolts and the two small coolant lines at bottom. I removed the bowl from the bottom and cleaned it all out, a shot of WD-40 in the valve body, hooked it back up and car runs great... the idle WILL be high during warm up. if you can let it warm up for about 5 minutes before you leave, you should be able to tap on the accelerator pedal and the idle should dropat least a few hundred RPM. As for the exhaust... our cars must be related,,, my exhaust rattles as the rpms pass through 2k before I shift into the next gear. Thought it was the exh. man. heat shield, mesh over premuffler... I let it go... Hope this helps.


thanks...i 'll definitly look into that valve and the connector...as for the exhaust rattle, i think i'll just take it midas...it's driving me crazy!

thanks again!

Not to insult your intelligence, but did you check all the hangers to see if they are worn or stretched?... The rubber grommets on my Jeep were stretched and dry rotted from years of hanging under there and when I replaced them, all was fine. Last thought, get underneath and pound gently but firmly on your catalytic converter with your hand, if the ceramic plates are broken, they will rattle and drive you nuts trying to hunt it down...

I didn't even think of that...rotten hangers. i thought they last forever...i'll check it out. it actually could be the cat...it looks pretty rusty, i wouldn't be surprised if it was busted internally. Its just weird because the rattle only occurs about 10minutes after driving the car. it must mean that something is warming up and getting loose.
Thanks for the knowledge...i'll definitly look into it. I threw some pictures up of my car, you should check it out...it's stock, but i just got it about 3 weeks ago. The body is in awesome condition witch is the important thing. I live in NH so most all of the preludes of this year are rotted out around here. Thanks Again.

tchach,
to fix your problem, put a japanese racing sticker that probably really means "me is stupid" across your windshield..and paint all your dash components yellow. that should quiet up the noise--and give you a little extra HP!! just a little rice-a-roni humor. Seriously though, tchach11 is my boy--he brought his 'Lude to meineke and they fixed that shit, it was a mount wire that was sticking out and they bent it away from the undercarriage so it wouldnt vibrate no more biach. They did it free too, (any dis i have given out to meineke in the past i take back!)

--we will race at the tolls when i fix my tie rod, but watch out, i might dry shot your ass with my NOS subwoofer--