I dont know where to begin this small story but i have a 94 Accord Ex with the stock f22b1. When i first bought the car it would bounce the idle up and down while under 25 mph every once in a blue moon. I would blip the throttle and all was fine till it would happen again about 2-3 weeks later. I overheated and warped the head so did a full engine rebuild. New head, block was cleaned and machined to turbo spec, seals and gaskets, alternator, trans(to be put in), plenum, intake, distributor, plugs, plug wires, iacv and fuel pressure regulater have all been replaced. Since the rebuild it has begun to idle up and down around 1000 rpm to 2,400 to 2,500 rpm constantly. Ive checked power to everything in the engine bay and all seems normal. If it helps it acts like the fuel pump is turning off and on because the pressure in the rail is rising and falling. I have no leaks and everything that has a gasket or seal has been torqued or triple checked for leaks, ive checked my coolant levels and made sure its going where it needs to go...

Any help is greatly appreciated and ill get back to any answer asap.

 

My first thought was IACV but you said you replaced that.

Ensure the engine coolant is bled properly and there is no air trapped in the system. After that try adjusting the fast idle valve on the throttle body. Cleaning the throttle body and adjusting the set screw may also help.

 

I know it sounds ridiculous but does your speed sensor / speedometer work? Whenever my speed sensor died, the vehicle would do strange things like this.

 

The plenum on my intake is from an f22b1 that didnt have this problem... dont know if that changes anything but its making me think its electrical somewhere... i read it cold be that my car thinks its cold even at 190 degrees. Could that be causing it to rev up and down??

 

Every once in a while my speedometer just drops to zero and then jumps and acts weird for a minute. After it does that it goes back to normal. Could it just be on its way out??

 

Like I said, check your speed sensor and make sure it is fine.


https://easyautodiagnostics.com/hond...sensor-tests-1

 

Went to this link and realized immediately, not sure of i said this but i have a manual not an automatic... pretty sure i dont have an output speed sensor on my trans.

 

it looks like you do have one:
https://www.ebay.com/itm/1994-Honda-...-/153512625171

 

The text under the pic says F22A1... i have an F22B1... I just dont want to spend more money and have it not do anything. I do have a spare trans from my donor car thats exactly the same as mine.

 

New trans is in and ill be starting it back up either today or tomorrow but with the "new" speed sensor still on from the parts car that didnt have my problem. If anyones still interested in this let me know and ill check some other things it could be

 

Look forward to hearing the outcome.

You can also check the continuity/resistance across both speed sensors to see if both are good or if you are looking for a different issue (or if both are bad?)

 

Idle is now bouncing faster when i start it cold and after a minute it slows wayy down but continues. Vaccuum leak maybe?? The only thing that hasnt been replaced or looked over is my intake tube under the plenum. Could i have warped it when i overheated my block a while ago?? I did have this problem from the get go but it was every blue moon and would go away if i blip the throttle.