mystery problem

[Jbyrd]

I built a 94 b18b1 for my 91 hatch. I wired it for obd0. When I start the engine and set the idle at running temp. it is fine, but as soon as I drive it the idle begins to fall to 400 rpm and rise back to 800 rpm with consistent rythem. There aren't any vacuum leaks and I did have to replace the IACV and the IATV (idle air thermo valve). I have an AEM Air/fuel gauge w/ the bosch wideband and the gauge indicates a 14.1 air/fuel ratio and rises to 16.1 when the poor idle occurs in sinc w/ the rpm. I have several years experience in building sportbike engines and have never come across this. It seems to me that the computer is receiveing a signal to alter the fuel/air ratio. The fuel/air ratio is acting the same at highway speeds as well. Just fyi I'm using- obd0 distributor, pr4 computer (have tried several w/ same effect), saturated injectors w/out resistor pack, stock compression, and have tried tuning with an SAFC with same results as above. This has had several local shops who have built 10 sec. 88-91's puzzled. Any replies of expertise will be greatly appreciated.

[1990civicdxhb]

I'm not too sure about the b-series,but I've found over the years,that not enough anti-freeze can cause the idel to go up & down,up & down,
this may not be your case,but its worth taking a look at.

[civickiller]

any air in your cooling system ?
since you replaced your iacv, im assuming it was brand new or you at least cleaned it before putting another one on.
take off fitv and screw it back in.

now this is assuming it isnt your iacv, iat, and you dont have any vaccum leaks

[superbluecivicsi]

tps and map sensor readings are?

[Jbyrd]

I have bled the coolant several times. My map pressure and throttle percentage doesn't fluctuate with the fluctuation in air/fuel. Is there a specific measurement that can be taken on either of these? I don't have the factory manual at this time but can refer to it on thursday. I want to thank each of you for your responses.

[cp___32]

I know it sounds sort of silly, but I had a similar problem and it turned out to be something to do with the battery cables. I just didn't have a really solid contact on the battery posts so I guess maybe what it was doing was sensing a slight drop in voltage so it was spooling up the alternator but it was just enough that the alternator only had to pump up the output for a sec then it stops....hence the cycle. It's worth a shot making sure everything is good, especially the MANY grounds Hondas have

[Jbyrd]

I just wired under the hood with 4 ga. Monster Cable from the battery to chassis ground, motor to chassis ground. I have had this problem for about 2000 miles prior to this. I did supect the engine ground to be the problem, but wasn't successful. Thank you for the feedback.