Crank_The_Boost

Hey guys, very new to hondas here, so here's the deal. Any help is appreciated...

1999 Civic SI with the b16 motor. 5 speed 'hydro-trans'...

Starved for oil, rod brearing spun, rod exited through block.

Car was given to me with (what I later found out) an OBD1 ecu.

Swapped a b18C OBD2 engine into it. Only things we had to modify were the motor mount brackets and timing belt cover I think... The engine we swapped in has the butterfly v-tec if that helps... Since the 1999-2000 civic si didn't have any wiring for the butterfly (we used the civic si harness) valves, a Skunk 2 intake manifold was ordered. Got that on the car, and can't get it to idle. The IAC is not doing anything. My good friend and master tech trouble shooted for well over 4 hours, and came to the conclusion that the computer isn't seeing engine RPM, so it can't give the IAC signal. we created a small vacuum leak on the intake mani to get the car to idle, but would really like to get the IAC to work.

Something to do with not having a crank position sensor on the old motor, or not having one on this motor...

Is there any way to get the obd1 P72 ECU to work with the obd2 wiring harness and obd2 motor?

93egSLEEPER

You will need a jumper harness to go from harness OBD2 to the OBD1 ECU.
OBD1 ecu's do not look for a crank position sensor.
I would also get the ecu tuned to disable the "butterfly effect" of the stock GSR.

Crank_The_Boost

The butterfly manifold is gone so that not in the equation.

Where does the b18 send out the tach signal for the ECU? What parameters does the IAC look at to control idle? RPM, TPS, and engine temp, no?

luvmihatch

iTrader: (3)

The stock gsr manifold is gone but your ecu is still looking for the butterflies, if it was me i would get a p28. which is a single cam vtec ecu and get the car tuned.. the tuner will be able to go in and disable the secondary butterflies which are associated with the stock gsk plennum

i liek running obd2 cars on obd1 ecu bc its easier lol... thats my opinion.

the only thing u will have to worry about it emmisions.


or

u can get a obd2 ecu and get that tuned and all the right things turned off so your car can run.

Crank_The_Boost

Okay, but the butterflies arent there first off, and second off it doesn't have a harness for the butterflies... It's got the OEM harness out of the 1999 civic si.

My problem isn't with the intake manifold, it's with the IAC... Why isn't my IAC functioning at all? p72 ecu, obdII civic SI (1999) wiring harness, with OBDII JDM B18C longblock...

mikeycivic

you cant just plug and obd2 wire harness into a obd1 ecu and expect it to work. You need a jumper harness like you have already been told.

Crank_The_Boost

Sorry, But I think the car has an adaptor harness already...

Suppose I do have a jumper harness, what else could cause the IAC to not get a signal? On the old motor, the crank sensor supplied the IAC with engine speed... now there's no sensor, so how is the IAC getting an engine speed?

luvmihatch

iTrader: (3)

Well you have a jdm motor in a usdm car.. so. one.. do u have all your emissions **** hooked up.. also check your vacuum lines. u said u gotta skunk 2 mani right.. make sure all the gaskets on all the sensors arnt pinched or there isnt any carbon build up.

and your running a p72 which is an obd1 ecu.so there is no suppose you have to be running a harness lol. i would pick up a obd2 jdm gsr ecu which is a p73 which knows thats u have no crank sensor. and see if u still get the same issue.

bc there is a big difference between what sensors the obd2 long block has that the obd1 doesnt and then on top of that you are using a jdm long block. lol.

luvmihatch

iTrader: (3)

or u can be really g. and go buy a new type r oil pump from honda for 100 bucks and use your old sensor. and walla u have a crank sensor.

HondaPartsHero

http://www.ff-squad.com/technet/ckftrick.htm

94EG8

You might wanna check your info. P72s come in both OBD1 and OBD2 varieties. The P73 is an ITR ECU. Both JDM OBD2 ECU and all OBD1 ECUs wont look for a CKF sensor. As far as the tach issue goes, OBD2B vehicles ('99 - '00 Civics, except HX, and '00 - '01 Integras) get their tach signal from the ECU. OBD1 and OBD2A vehicles get their tach signal from the distributor. When running an OBD1 or OBD2A ECU in an OBD2B car it is neccessary to run a wire from the igniter in the distributor to the tach test wire at the driver's side rear of the engine bay. Wont affect the IACV though, the tach signal never even goes to the ECU on an OBD1 vehicle. Btw, did you bleed the coolant? Air in the coolant will cause a high and sometimes fluctuating idle.

Crank_The_Boost

There is no coolant issue.

The car WILL NOT idle at all if the vacuum lines are properly hooked up. In order to get it to idle, we had to unhook the cruise control nipple on the manifold, so the engine could get SOME air in at closed throttle.

It idles smooth at like 800 (miraculously) but when you give it throttle, it revs up to a certain point (maybe like 1800RPMs or so) and begins hitting either fuel or timing cut. It sounds like a 2 step. The more throttle I give it, the harder it bucks, until I give it enough throttle till it breaks free and revs up.

when driving it, same deal. bucks HARD till it gets to like half throttle, then it jumps past 3000RPMs and drives like normal.

I'm positive it's IAC related...

Crank_The_Boost

Okay guys, thanks for the help so far, but I've got one last bump for this thread:

Is it possible, to "fry" or damage a computer due to having the IAC, MAP, TPS, or coolant temp connectors interchanged?

For example, if I had the IAC connector on the wiring harness going to the TPS, and the TPS connector on the harness going to the MAP, and the MAP to the IAC, could I short circuit or harm the computer? Wouldn't it just send the wrong voltage to the part/pcm, making the temp sensor, TPS, IAC or MAP read incorrectly?

Thanks again guys! Honda-Tech is FTW!

00PhillySi

No possible way to harm the ecu by plugging the wrong connector onto the wrong sensor.

However, to go back to your earlier post, that "2-step fuel cut" feeling you're getting is the pcm putting you into limp mode because it knows better than you do, and is stopping any potential damage to the engine. This limp mode can be achieved by multiple things but iac problems are not one of them. Especially since the iac has no effect anywhere past idle, and you said it 2-steps then jumps to 3000rpm

Crank_The_Boost

Right, but think about this-

The TPS % vs IAC voltage vs MAP signal correlation is off if the throttle body is doing the IAC valve's job. I think the 2 step issue came somewhere from within the idea that the computer was seeing (X) voltage of TPS and (Y) signal from the MAP, and the correlation was off (since the IAC was not letting air by) so the comp lip'd it until it passed the TPS vs MAP correlation issue. Understand what I'm saying? Drivability past 3K was perfect, with the exception of a dead spot in the TPS at like 4.03V or something.

Crank_The_Boost

But Philly I also don't think that a mis-matched connector could fry an engine computer. I would hope not at least, since the car had 5 different connectors that reached the TPS, and they all fit perfectly...

speedooo

Oh my lord this thread is full of misinformation.

So let me get this straight, you have a jdm gsr motor w/ a skunk2 manifold in a 1999 civic si and you're using an obd1 ecu.

Yes, a usdm motor has a crank position sensor located in the oil pump housing, but don't worry about that because you have an obd1 ecu.

Does your tach work? Does the car run and drive? Then your ecu is most likely receiving an rpm signal, which btw is a blue at the cluster, and is probably also a blue wire at the distributor and ecu but don't quote me on that.

Your idle issue is most like a vacuum leak or faulty/dirty IACV. Try placing a piece of gasket material between the IACV and intake manifold and crank the idle adjustment screw all the way open. Do you have a cel for the IACV? It's common that you won't get a cel for the IACV because it's producing regular resistance so the ecu thinks everything is okay. If it's a mechanical issue like a vacuum leak (bad gasket) the cel won't turn on.

Crank_The_Boost

You fail here, read, the car runs well enough to make it from Florida to North Carolina and back two times with NO issues, and has had no issues aside from idle/just off idle. The Tach works just fine BTW

You fail here. I have checked with a multimeter, and there is no voltage being sent TO the IAC. The car has a vacuum leak right now to let it idle. I am aware of this, and without it, the car will not run, at all

Apearantly you were misinformed about the Skunk 2 manifold... It has no idle control screw. Thats strike 3

Never saw a check engine light. This is because, I was just recently, informed that the bulb had been removed by the 'previous owner'...


Talking about misinformation... Anywho... Anyone have any more input on the ECU frying issue?

Former User

It is possible to fry the ECU by swapping sensor connectors.

The IACV gets voltage on a Yel/Blk wire from the main relay. It should have battery voltage with the key in ON(II). If not, check for a break in that wire.

Install a new CEL bulb asap so that you can pull the CEL codes.

Crank_The_Boost

Ah, this looks like a possibility... A relay that sends battery voltage definitely has the ability to fry a PCM, if the PCM is looking for a 0-5V reference (TPS for example) and it gets 12V... Would anyone like to back this guy up? I don't recall off the top of my head what color the wires were, but if thats the case then that explains a lot...

94EG8

Yep, you can fry an ECU by swapping connectors.

Crank_The_Boost

Wow, well thats agrivating lol

Why would honda put 5 connectors, all within teach of any sensor/part that are all interchangeable if they can don't all use 5 volts?!?!

I call failure on honda engineering!

speedooo

I actually was not referring to you when I said misinformation, that was aimed at things like the p72 and p73 comments...

The idle screw is on the throttle body you twit. Thanks for the sweet red typing.

94EG8

Because it's cheaper to use 1 style of plug instead of 5. You learn to memorize the wire colors early on if you do any amount of engine swaps. IAT sensors and ECUs add up pretty quick. (ECU can usually be fixed btw as long as you know someone competent with a soldering iron)

JDMEK4life

Seems like you are a little out of you're league. Listen to the advice given! I also have a 2000 EK civic Si, with a (recently)fully built B18B1 bottom and B18c head. It used to be a stock B18c. At that time, I chose to run the P73 due to the crank sensor issue. Although, I am pushing lubricant with a typeR pump now and have a Hondata S300 piggyback. It's just a better setup! You should look up Katman's, of FFSquad, diagrams. He is awesome and was the first one to figure out how to properly run a JDM B18 in an OBDII USDM Honda! His diagrams will tell you how to fix any and all wiring issues that come with doing this swap! Do some research. Most likely you have not properly wired up the ECU and as a result you're ECU is not receiving all the signals it needs and cannot do its job properly. I had the same issue at first, but that was years ago and after much reseaech and many headachs I found out about Katmann's info. It was a blessing and very easy to follow if you have any bit of experience! You can also contact Katmann via email, I did. Give him a few days to respond, he is very busy! Hope this helps you out! And bumps for the Si! Good luck! PM me if you like! I might be able to help more.-JSpeed