Prelude Idle problem - Honda Prelude Forum

pacificarage · 01-22-2010, 10:22 PM

hey guys, my prelude is having an issue with idleing. almost anytime its in neutral, it keeps revving up to 2k rpms and then back down to 1k rpms. it will go back and forth all day long. its not gradually either; it moves back and forth at a steady speed. the gauge just wont stay still. i dont really know what to do in this situation. if someone has experienced this problem or knows anything about it, the help would be greatly appreciated. thanks.

kimara3002 · 01-23-2010, 05:01 AM

try these

-Adjust Idle screw on Throttle Body
-Bad MAP sensor
-Throttle Positioning Sensor
-Clean Your IAC Valve (really easy)
-Possibly air in coolant lines
-Vacuum line leak

pacificarage · 01-24-2010, 08:12 AM

Quote:

Originally Posted by kimara3002

try these

-Adjust Idle screw on Throttle Body
-Bad MAP sensor
-Throttle Positioning Sensor
-Clean Your IAC Valve (really easy)
-Possibly air in coolant lines
-Vacuum line leak

thanks man, i try out those things. i have also yet to try and replace my oxygen sensor. that might be related. i did replace my IAC valve though. but ill try the rest.

minilogoguy18 · 01-24-2010, 11:32 AM

Sounds like the fast idle valve, it's on the underside of the throttle body, held on by 3 10mm bolts. Remove it and take the cover plate off the back and use a flat bladed screwdriver to screw the plunger all the way in then back it out about a full turn. Both TPS and MAP sensors will throw a CEL if they're bad so if you're not getting one then they most likely aren't the culprit. I had the same idle as you, would climb up to 2k then drop and bounce like that.

pacificarage · 01-24-2010, 08:31 PM

Know of a good write-up?

minilogoguy18 · 01-25-2010, 09:41 AM

Honda Fast Idle Valve (FIV) - Pulsing Idle Fix - JDM Universe.com

It's for a different engine but pretty much exactly the same. I'd use some thread locker when putting the cover plate back on, my first FTIV had it's plate fall off while driving.

pacificarage · 01-31-2010, 10:16 AM

so i tried getting to this valve. i cant seem to get in there. id rather not have to take anything else off. in the write up, it show him taking the whole piece out of the bay. gah. and btw, my CEL does come on. ive noticed it tends to come on at about 30 mph. im about to pull my hair out. haha now i think my master cylinder is leaking hyd. fluid. balls.

valiente540 · 01-31-2010, 02:08 PM

i'm having the same issue. i cleaned my IACV and now it seems to idle at around 1100rpm. Should i just clean it again or should i try the idle screw on throttle body?

indylude18 · 01-31-2010, 03:09 PM

Quote:

Originally Posted by pacificarage

...

Pull the CEL code.

kimara3002 · 01-31-2010, 03:11 PM

try the idle screw on the TB

indylude18 · 01-31-2010, 03:14 PM

^That isn't a real solution, only a temporary quick fix.

valiente540 · 01-31-2010, 03:24 PM

there is no CEL on so its not a sensor. right?

indylude18 · 01-31-2010, 03:28 PM

^Not necessarily. Some sensors or valves won't cause a CEL when they go bad. Please start your own thread if you are going to keep asking questions.

pacificarage · 02-04-2010, 10:22 AM

Quote:

Originally Posted by indylude18

^That isn't a real solution, only a temporary quick fix.

that's what i was thinking. i dont want to fool my car. i want it running the way its supposed to be.

minilogoguy18 · 02-04-2010, 06:52 PM

Well the IACV will throw a CEL and also cause an idle bounce but like said, pull the codes first.

pacificarage · 03-26-2010, 10:10 PM

Well, I finally got around to finding the problem. I swapped the fast idle thermal valve and it fixed it. My check engine light still comes on, so I dont know what's up with that. It's running a little rough. :/ But hey, I appreciated all the help from you guys.

SNsLude · 03-26-2010, 11:00 PM

Pull the code?

pacificarage · 03-30-2010, 10:20 AM

Well, I would but i dont have a scanner, and O'reily's won't scan one if it's an import OBD-I car. I heard about using a jumper on the cable under the console, but it says you can't do it while the car is running. On my car, the CEL comes on at about 30 mph. So, I can't do that. It's pretty weird.

Smoothrigoletto · 03-30-2010, 08:05 PM

Quote:

Originally Posted by pacificarage

Well, I would but i dont have a scanner, and O'reily's won't scan one if it's an import OBD-I car. I heard about using a jumper on the cable under the console, but it says you can't do it while the car is running. On my car, the CEL comes on at about 30 mph. So, I can't do that. It's pretty weird.

OBD1 is quite easy to read the codes and you can do this at home. just jump the blue connector underneath your dash. Ever heard of that? use a paper clip to jump one pin to the other. You'll know when you jump it right, cuz the engine light will blink a series of flashes. Good luck

pacificarage · 04-15-2010, 10:29 AM

Quote:

Originally Posted by Smoothrigoletto

OBD1 is quite easy to read the codes and you can do this at home. just jump the blue connector underneath your dash. Ever heard of that? use a paper clip to jump one pin to the other. You'll know when you jump it right, cuz the engine light will blink a series of flashes. Good luck

well, thats the jumper thing i was talking about. I didnt think it would work, because the car isn't supposed to be running when you do it, but somehow, it worked anyway. It led me to the Idle Air Control Valve (IACV) which is very ironic. I cleaned the connections and now it surges when it idles sometimes. haha I think i need a new one.