Mighty

When I had my B18b swapped in it idled good but when I switched to Uberdata and a chipped P28 for my turbo setup the idle started surging. When it first started it would idle at 3000 rpm for a few seconds then drop down to 2000 rpm then a little bit after that it would start surging with the idle going from 1200 to 1800 rpm. This was very annoying and probably not good for the motor. The car idled fine once it warmed up.

I did some research and people said it could be caused by various things:
- vacuum leak
- coolant needed to be vented
- dirty IACV

Finally someone mentioned that OBD1 engines have a FITV and my OBD2 didnt have one and thats why the OBD1 computer wouldnt idle it right.

After some thought I decided to use some washers to throttle the air to the IACV. A #12 washer fits against the screen of the IACV perfectly. But the large hole in the #12 washer allowed the car to idle at 2000 rpm and it still surged. So I then took a #8 washer and glued it to the #12 washer with RTV. The smaller hole in the #8 washer prevents the car from idling over 1500 rpm and it stopped the surging. The car now idles perfectly when cold and warm. You could also try a #10 washer if the #8 is too small.

Just posting this because it seemed to be a somewhat common problem.

type Gendy

Good find John

JBBNJ609

jw what are these # with the washers, where do i get these washers ??

Mighty

You know how machine screws come in sizes like 10/24 or 8/32. Well a #8, #10 or #12 washer is the washer that is sized for a #8, #10 or #12 machine screw. Its probably some sort of metric sizing which is why it fits so perfectly in the Honda IACV. Anyway I got them at Lowe's but you should be able to get the at any hardware store. They are just a small washer.

donkiman

i just swapped a 98 gsr motor into my 97 civic. I'm running chipped p28 ecu. I read your post about this but i have 2 problems. #1 is that it does idle at 3000 rpm and then goes to 2000 and then from 1200 to 1800. #2 is that coolant will not go from my radiator into my motor. I was told to change thermostat and water pump. does this sound accurate? and also what is this FITV that obd1cars have? I want to fix the radiator problem and then i will use your washer technique to fix the iacv. also to your knowledge is the thermostat and or water pump from my old d dseries motor interchangable with the gsr motor. thanks alot.

Mighty

The washer fix will probably fix your idle. Idle problems are also caused by coolant problems so you need to fix that first.

The water not getting to your radiator sounds like a thermostat. It could be your water pump but is most likely the thermostat. Buy a new thermostat (theyre cheap) and try it. If it doesnt work then its your water pump.

FITV is fast idle thermo valve. On OBD1 cars it is open when the car is cold so that they idle fast when cold and then it shuts as the car warms up allowing the IACV to take over controlling the idle. I dont think adding a FITV will fix our problem. If we had no fast idle then the FITV would fix it, but we have too much fast idle. Our problem is the coding for Uberdata is not right for OBD2 cars. The right way to fix would be to write new code. Im not a computer programmer Im a mechanic so I fixed it the mechanical way.

By the way if you drive the car before it warms up with the washer fix it will still bog like it did before the washer fix. The washer fix only fixes the idle.

willyboyK20

my problem is a little on the line like yours instead i put a stock p28 on my d16y8 and it
would idle around 300-400 rpm like it wanted to die and from time to time it would idle up and down for 500-800. The next day after i put it on it wouldn't even start until i reset it ( no codes either) I'm thinking maybe the conversion harness may have something to do with it.

Mighty

Did it fast idle at all? If not then maybe a FITV would fix your problem.

Also you can adjust your idle if it is too low.

I doubt theres a problem with the conversion harness.

JBBNJ609

well i have an obd1 gsr (p72) im gonna be breakin in the motor soon and i dont want that damn surging idle for a brand new rebuild . . . what do you think i should try ?? thanks

JAY

Mighty

Yep give it a shot. If you get the #12 washer it fits perfectly and cant fit through the hole and cause any problems.

JBBNJ609

which hole do you put it on the one wioth the filter or the other ??

can i put it on both sides ?

and can i put a washer on that hole for the fitv( the one thats the same size as the iacv one)