my friends 90 4 speed won't idle straight..it revs up to about 1.5k...and then drops to about 500..revs up..drops...it won't ever stop...what sensor do you think might be bad? i read once upon a time what it prolly was, but i forgot (btw, it is NOT the dizzy that's the problem)

Vacume lines, and vacum pot on the idle control :)

My guess is a lose or worn vacum line, or failed vacum idle control pot solonoid thingy. (there are about 10 differnt names for these things, I tried to find one for my car, and the 3 techs at Honda all called them differnt things, then the Honda Parts CD listed them as something else!)


Of course the USDM Civics are a little differnt to the JDM ones, so I could be wrong.

I had a similar problem and changed all the lines - it fixed it although I occasionally get a wobble from 600 to 900 - nowhere near as bad as it was before though.

As per Moppie - this was on a JDM car.

do you mean all the vacuum lines?

it could just be one shot line causing it, but it is generally easier to just replace them all, you can get the silicon tubing in many colors for like 15 bucks generally

^
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not neccessary saying it is the vaccum lines causing it, however it is a good possibility

Originally posted by gotatight92si
do you mean all the vacuum lines?

Yup :)

mess with the idle, thats just what i did w/ my car when it did that. Just get a flathead screwdriver and turn the idle screw to where it will stop doing the fluctuation.

i say to check the Throttle Position Sensor, and your fuel pump.

yeah...we're going to change the fuel pump today..he's got a good spare, so might as well. i guess if that doesn't help, we'll do all the vacuum lines too. and maybe that thing moppie was talking about with like 15 different names :) if the TPS is bad, how much will a new one run?

about 700 from the dealer, no one else can get it, b/c it's part of the throttle body, i'm up the creek on that one, i'll prolly just go to a yard and get one for my dx one of these days