95 si, funny cold idle........ - Honda Prelude Forum

ludeboy95 · 11-13-2001, 08:14 AM

After letting my car warm up for a bit, the i drive a very short distance (less than a mile) put the car in park, the idle
sits around 1700 then quickly jumps to around 2800, then back down to 1700. It is almost like a heartbeat. Up down up down.
It only does it a few times then back to normal. What is this, Cold idle sensor?
I've had the car for a year and it never did it before.. Help me please...

www.hondaprelude.com/ludeboy95

CrazyKid · 11-13-2001, 01:05 PM

ok i have never exerianced this problem on a prelude, but on a DSM they do this all the time... the idle surges up and down.. its annoying. i have a freind who has a DSM, she had this problem... so i researched ito ut for her after the dealer told her $600 to fix the problem. it turns out there was a BISS ( base idle set screw ) that had becone missing in action ( it fell out somewhere ) so i found the part # and went ot the dealer and ordered the screw ( 2.47 ) so.. put it in and poof... it works fine now.. no surgeing idle so i dont knwo if this will help... but look for something liek that on the prelude it was on and around the throttle body, or chech your MAS.

Bill

marcucci · 11-13-2001, 01:28 PM

On a Prelude this is almost always due to a throttle body coolant line bypass. There are coolant lines running to a thermo valve in the TB, which alter the base idle when cold. When bypassed, in cool weather, the idle can bounce up and down.

Look for the two coolant lines underneath the throttle body (going into the valve bolted up underneath it). Make sure they are there, and connected, and aren't just looped back around on each other. If they are there, make sure they aren't leaking and you might even check to be sure they aren't clogged. Now might be a good time, with a car that age, to flush the coolant and replace the thermostat, as well.

Don't dick with the idle screw unless it's missing. I've never seen one come out of a Prelude. Your problem is an idle control, messing with the screw will just change the idle speed, not affect the oscillation (which shouldn't be there).

prelude555 · 11-13-2001, 04:08 PM

idunno if this would help..recently my car had the same problem. idle jumps up n down (very annoying) therfore i brought it to one of my friend see wuts the problem, he said my carburator was dirty so i took it to a shop an clean it out for 40 bucks.an now the car runs fine.hopefully u have similiar prob. gl

cantdrive55 · 11-13-2001, 06:22 PM

Quote:

Originally posted by prelude555
idunno if this would help..recently my car had the same problem. idle jumps up n down (very annoying) therfore i brought it to one of my friend see wuts the problem, he said my carburator was dirty so i took it to a shop an clean it out for 40 bucks.an now the car runs fine.hopefully u have similiar prob. gl

um...unless you have a 2nd or 1st gen, your car is Fuel Injected.

prelude555 · 11-14-2001, 02:44 AM

its a 95

ludeboy95 · 11-14-2001, 06:26 AM

Ok, today it did it about 2 minutes after i started it. up down, up down. I was thinking O2 sensor? I'm gonna have it put on a machine this weekend. It is running really well other wise. Thanks for all your help guys...

www.hondaprelude.com/ludeboy95