My car is a 1998 Honda Accord ex 2.3l vtec with standard trans. My idle is surging and I don't know what else to do. I have replaced to iac, tps, map sensor, throttle body. I have 3 stepped it, burped the cooling system, did a couple idle relearns, checked for vacuum leaks and then double checked for vacuum leaks.

When it first happened I got a 1590 code (iac circuit malfunction) and then the fun started. I replaced the iac ( all new parts nothing used or from a junk yard) and nothing changed. Then I kept replacing parts and nothing has changed at all. Starting to think of its the Pcm.

I really need help. I'm loosing my mind over this car. Any ideas would be great. Thank you so much for your time

 

Are you still getting the P1590 code?

 

No I am not getting any codes at all

 

Ok so my car idle is surging. When I start the car it will idle around 2k for a couple min. Then it will go into a surge. It will idle between 1 and 2k. I have noticed if I rev the car over 5k (quick rev) the surge will go away and idle perfect. It will hold a perfect idle until I start driving again.

I have replace the following.

Iac valve
Tps
Map sensor
Throttle body
Coolant temp sensor
No vacuum leaks at all

I have burped out the cooling system to many time to count. I have also pulled the number 13 fuse and tried a idle relearn. I'm running out of ideas here. Is it the pcm? Are there any other test to do? It's driving me crazy.

Thank you for your time.
Josh

 

Is there some slight slack in the throttle cable allowing the throttle plate to close completely? When the car surges at idle, try twisting where the cable turns the throttle plate backwards to see if something is getting caught up.

 

I also merged to your other thread, so we don't have two different threads trying to diagnose the same problem.

 

Thank you. New here haha and no slack in the cables. That was one of the first things I checked

 

You need some slight slack to allow the throttle plate to close completely.

On my old 95 accord, I didn't get the cruise control cable installed properly when reinstalling my throttle body. It was preventing the throttle plate from closing completely and causing idle problems. Its something simple to check as well.

 

EDIT: I also moved some other posts from another thread about a 2000 V6 issues into this one so there might be some confusing timelines, posts in this but at least the one issue is in one thread.


I'd recheck the work done on the car just to be sure......throttle cable has to correct amount of slack, TB gasket is good, ect.

I'll assume the bouncing only happens once that car is warmed up, normal op temp.

If you cover the lower port inside of the TB with your fingers, what does the idle do....no change, lowers but still bounces, lowers and the bouncing stops, ect.

 

I did double check everything about 10 times. I have been working on the car for about a week now. There is slight slack the in throttle cables and the plate is closing all the way like it should. It does only stat surging when the car gets warm.
If I cove the hole closest to the passenger side the car will idle very low and the sure will stop. It looks like that's the hole for the tps. By covering it slightly the car will idle fine and everything is ok until I uncover it.
I do have a snap on scan tool hooked up to it and the specs on the you are perfect