I just recently purchased a 1994 Honda Accord lx. It started a surging idle. Idles high until it warms up. After it warms it surges while in any gear. When driving it surges at a stop sign and stalls while driving and then jumps hard and goes then does that over and over. I've replaced plugs, wires, distributor, idle air control valve, throttle position sensor and fast idle valve. I've also bleed the coolant system. Still no luck. I was told that the timing could be off. Someone please give me some advice!

 

Check this out about setting the "base" idle.
https://www.hondaaccordforum.com/for...e-speed-38734/

You've already done a lot of that, but make sure you do a good check for vacuum leaks. And check that the throttle plate closes fully and that the throttle cable is never used to adjust the idle. Then do the process of resetting and forcing the ECU to re-learn the idle.

Did you get a used fast-idle valve? Sometimes they get loose inside. There's some threads about taking off the cover & tightening the plunger inside. (I don't have firsthand experience with that)

 

It was a new fast idle valve and new iacv. I have looked for vacuum leaks but I will double check everything. If I can't find any then I will try resetting the ECU. Thanks for the help. I will let you know if this gets it. 💪

 

Regardless if you find anything, it'll probably help to reset & relearn anyway. That's normally done whenever anything changes in the idle control system.

The other thing is don't be taken back by the very low RPM of the "base" idle; that adjustment made with the IACV unplugged, is designed to put the IACV in the sweet spot of it's control range. The idle control system doesn't get along well with people adjusting higher for "personal preference".

 

Ok so I reset the ECU. Checked for vacuum leaks. Everything seems as it should. I unplugged the iacv, set the base idle to 550, reset the ECU, still surging. Any other suggestions?

 

Check that you didn't switch the map sensor plug with the throttle position sensor plug. They are identical. The map sensor wire colors are yel/wht, grn/wht, and wht/yel. The TPS wire colors are grn/blu, red/blk, and yel/blu.

Pull the snorkel from the throttle body, and let the engine start surging. There are 2 ports inside the throttle body. Use your finger to block the lower port. Does the surging stop?

Did you reset the ECU by pulling the 7.5 amp backup/radio fuse in the engine bay fuse box?

Check that you have some slight slack in the throttle cable,so the throttle plate is completely closed. If you tightened it too much, then the throttle plate may be slightly open.

Another potential issues is the throttle position sensor. You purchased and installed a new one. Did you get the sensor keyed with the throttle body post? You can try back-probing the red/blk wire to the sensor and checking that you have around 0.45 to 0.50 volts to ground. There is an adjustment on the TPS you should do when you install a new one.