toofast4u

98 honda civic hatch, stock, when car parked in neutral rpms are revving up and down continously, goes ok when i start driving the car, also in a morning its ok. any idea? i have recently installed new radiator and someone said it might have a air in radiator ... need ur suggestions ...

chris_v2

It might be air in the system, however a more likely cause would be the IAC motor.

slowandfurious

could be a faulty tps or iac valve. try cleaning the tb with some tb cleaner

F8i

iTrader: (10)

2nd both of those:
IAC, or TPS.

Google how to clean your IAC sensor, if that doesn't work... you might need to by a throttle body.

iamcanadian_31

its definately sounds like your throttl position sensor... mine was doin the saem friggin thing for time... and i tried dicking around with the ICV and everytime i unplugged the iacv it would idle fine... plug it back in and rev it up ,it went right back to the fluctuating idle again...i checked the TPS to see if there is adjustment and sure enough...

i used to have a d16y8 and the TPS was riveted on(not adjustable)... i have a b16a now and the TPS has 2 torx screws .. dont take them right out, just loosen them (if theyre not the rivets) and adjust the TPS a few degrees either way while at idle and it should smarten right up... it worked for me... i didnt even have to take anything apart or clean anything

lemme know how it went

zeeman

iTrader: (1)

JDM engines have the TPS's held on with torx screws but any USDM/CDM engine i've worked on or seen has the TPS revitted on.

A jumpy idle can be caused by a small vacuum leak, air in the cooling system, faulty or dirty IACV or even a misadjusted Fast Idle Thermo Valve (if equipped, but a 98 civic doesn't have one)

Dangles

You might have to re-calibrate your tps, there is a way to do it by see what the output voltage is, but I'm not 100% certain of the top of my head on how to do it. But if you were to search google I know you will come across something because i've read many topics on it previously in the past.

Martin_vtec

iTrader: (1)

check your coolent.

clean the iacv and if your car has a fast idle thermo check that out..

gotta be one of these three..

probably the iacv....

Tyson09

iTrader: (1)

i think this might have just helped me out as well, been trying to (self-tune) my car and it runs fine above 1100rpm, having it sit there at idle it bounces, when i would drive it and push the clutch in, it would stall, or sometimes it would idle fine for 2 mins then all of a sudden start bouncing again, could this be my issue as well?

zeeman

iTrader: (1)

the TPS should be reading 0.5V when closed and 4.5V when wide open. The voltage should also increase smoothly when opening the throttle.

Tyson09

iTrader: (1)

and since im running 1000cc which are near impossible not to run rich my tb is probably all covered in carbon and such

Tyson09

iTrader: (1)

ok so my tps is running at 0.54 volts, were you talking bang on 0.5 or is mine still considered the range?

zeeman

iTrader: (1)

nah, thats fine.

I've found with 1000cc injectors typically you need to run a little richer at idle to have a smooth, consistant idle.

Now if you're using the new Injector Dynamic injectors this is not the case.

nsxvtec

For the TPS if you need to, those are not rivets on the TPS just special screws that Honda likes to use to try to confuse peeps and keep you at bay.The screw head breaks off once tightened up to spec from the factory.
Just use a Dremel or hacksaw to slot what looks like the head of a rivet and presto, you can then unscrew and replace them with the screws of your choice or reuse them.

Tyson09

iTrader: (1)

damn i wish you were closer i'd have you tune this thing, i cleaned the TB and watched the ems, it sits around 0.52 now and runs smooth when i press the gas. Topped up the rad and ran it to take any bubbles out. The vacuum is running around 18 on my boost gauge but on the ems the engine load is around -8psi. I am starting to wonder if its just my fuel map making it bounce.