LyFeWoRx

hello,

I have a h23 in my 4th gen prelude, i replaced the TPS sensor and set the tps to .45 like it says in the manual. The idle is bouncing from 1500rpm to 2500rpm and it wont stop.

The reason i replaced the sensor was because my old one was cracked, it wouldn't idle worth a damn it would just hold at 3k.

Since i put the new one on i can't seem to get a steady idle but the CEL(code 7) is gone.

Does anyone have any ideas on what could be wrong? Could the sensor be bad?

Thanks,

Michael

LudeyKrus

Vacuum hose, probably. Check for open nipples and cracked lines.

LyFeWoRx

Its wierd that it didn't do this before. I checked the lines and you would think i would hear the leaks, is there a way to preasurize the system without the car on?

LyFeWoRx

anyone?

yellow_jacket

No, you can't pull a vacuum on the system with the motor off.

Just looked for cracked vacuum lines around the throttle body. I would also clean the throttle body out. If the idle air control motor is dirty, it can cause these problems.

LyFeWoRx

is there a FAQ on this? cleaning out the throttle body and Idle air control motor?

PreIudeSI

try this: Take your intake off and start the car. Let it idle (or let the idle bounce). Now there are a few holes in your throttle body for air to pass into sensors like the iacv, or the fast idle thermal convtol valve (which hole goes to what sensor is irrelevent to us in this situation). Hold your finger over one hole at a time. If the idle goes to normal, follow that to the appropriate sensor, replace that sensor. Fixed.

silent dave

do what PreIudeSI said. my guess is that the fast idle thermo valve is the problem. if it is you should take it off then shake it. if it rattles. then the actual vavle inside came loose and you should be able to disasemble it and tighten it up by screwing it back into the vavle housing. probably terrible directions but hopefully you'll figure it out

ColinKAccord

ive dealt alot with the tps. most likely its the calibration. try bumping the voltage up a little till the motor stops surging. tps cant just be set to a certain voltage, theyre calibrated to each motor, thats why honda uses rivets, not screws to hold them on, so you wont mess with them,

its not easy to get it right, it takes alot of trial and error

LudeyKrus

a TPS w/ bad voltage won't cause a surging, though. Mine was off voltage when i replaced mine, and i turned it completely each way and it didnt' surge, it just affected the idle.

Superman137

sorry for jacking the thread but I was wondering how do u set the calibration .

LudeyKrus

You loosen it, check the voltage, and turn it till it gets to the right voltage at idle. You then tighten it back down.

You can use a multimeter and touch some bare wires, but I just used my VAFC's "sensor check" screen to read them.