Hey guys, I picked up on a Em1 w B18C swap like a month ago & I noticed the rpm would surge on warm temperatures when I’m in stop sign or light. At first Ithought it can be a vacuum leak due to the intake it had the air filter didn’t had a clamp on so the air filter w tilt out & leave a crack open. I bought a AEM cold air intake for it & thought that would solve the problem but it did not. I noticed there is a sensor on the manifold without a plug in it, did some research & the symptoms for a faulty or missing AIT sensor were pretty much accurate w some symptoms I’ve been having. When i accelerate it sometimes jerks feeling likes it’s not having enough power & the idle surging up n down from 1000 to 1500 RPM when motor is warm in temperature… so itried looking for the plug but can’t find it anywhere on my harness, there’s a plug that’s just hanging but the plug look totally different then what the output of the sensor ihave in the manifold is. Would this be due to the harness being from the Em1? & if it can I changed the plug from the harness or what is the solution to this? Pls help!

 

Do you have a check engine light on ? If so, what codes are present ?

Next, post a picture of the sensor that is unplugged. It is quite common that '96-00 Civic owners use the IAT sensor that is originally mounted in the intake inlet tube... and the plug that connects to it from the original engine harness has a black clip and the wire colors are red/yellow and green/black. It is likely that the B18C will ALSO have a IAT sensor mounted into it... and you don't need TWO of them, so it is not uncommon to see one left unplugged in this application. Now, here is the rub: If you have a OBD-1 ECU using either some type of chip or engine management, it is BETTER to use the IAT sensor that is mounted in the intake manifold instead of the one in the intake tube. This will require one to lengthen the wiring and change the plug to a grey round plug. Check to see what type of ECU that you have and report back. The idle surge could be from an improper coolant fill/bleed.

 

first off Iwant to say Thank you for replying! & no CEL brother, ima going to attach the pics I took rn of what u ask me & sorry for my ignorance don’t have much knowledge about ecu but mines has written P72 JUN is this a OBD1?

 

B18C type R has IAT in the intake manifold runner. Newer OBD2 cars has IAT mounted in the intake pipe. Yours is connected correctly, as I can see in the second picture (sensor with green and red wires coming to it).

Leave the second redunant IAT on the intake runner as it is or fabricate a blanking plate to keep cleaner look.

 

my ecu has written p72 jun, this is a obd2?
so pretty much with what you’re telling me the IAT is not the culprit making my rpm surge up & down at idle when engine is warm? Sometimes when I’m cruising the car jerks on me like it’s loosing power or something.

 

P72 can be either OBD1 or OBD2, but since yours is B18C, I'd guess it is OBD1.

Well, if sensor is plugged it, it does not mean it is working correctly. There is a graphic in Honda manual with temperature/resistance of the IAT, so you can check with multimeter if it matches.

There might be other reasons, like vacuum leak.
Maybe others can give better suggestions, cause I have just recently got back to Honda after 10 years, so my knowledge is a bit rusty

 

Does your P72 ECU plug directly into your original EM1 engine harness or do you have an adapter/conversion harness to plug the ECU in ? If it is the latter, please take a pic of the part number on the side of the ECU and a shot of the ECU plugs and post them here. Also, a pic of the inside of the ECU (remove the lid) will show what the "JUN" sticker means.

 

for sure thanks for the input, & welcome back my friend (:

 

ok I’ll take some pics of the connections & the ecu but when ichecked the “p72 jun” is written in marker. Btw last night iwent for a ride & noticed when I’m cruising at 3000 rpm the car tends to slightly jerk, & when I tried taking off from a light it almost shut off on me. Ifeel like the situation is getting worse

 

The thing is, a P72 ECU is for a "GSR" engine... and you have stated that you own a "Type R" (and certainly the photo above with your intake manifold visible suggests this to be true). So expecting your engine to run perfectly when you obviously have the WRONG ECU is a stretch. Now this doesn't mean that other issues aren't creeping in at the same time here...

Running a 200 HP engine with a 170 HP computer means that in all likelihood, your engine is running lean everywhere. This would explain the slight jerking at 3000 RPM.

 

it makes a lot of sense what you’re telling me, atm I’m not home rn but when I get back I’ll take the pics & post them up here of what u ask me so we can confirm! Thanks a lot bro, I truly appreciate the time your taking to help me out w this issue I’m having.

 

Ihope these pics can help you give me a answer, & also if ido have to change the ecu, am I going to have get a new connection or something so it can plug in right away?

 

How about a pic of the edge of the ECU where the part number and serial number are. The part number will be 37820-P72-XXX where the "X's" denote the Country of origin and the program version. If you want an actual ITR ECU, you will have to purchase another ECU conversion harness as the one that you have pictured above is for OBD-1 plug style ECU's, and the P73 never came with that plug type. If you get an OBD-1 ECU with a tuning solution, you can use the ECU adapter harness that you have now.