D16Y8 to D15B Engine Swap Issue

dhudge

New Member
I have a 99 civic ex (D16Y8 VTEC) I swapped out for a JDM D15B VTEC (Tiger Japanese - Home). Had a local auto shop do the swap.

The problem is it has a high idle, cycling between 1600-1800 rpm @ ~ 1 Hz increments and with a load, below the idle rpm, the car buckles and acts as if its gonna stall.

Other similar threads suggest I have the incorrect ecu for the D15B and should use a P72 ecu and chip it for the d15b, or that an obd1-to-obd2 harness conversion is needed. The shop owner thinks it's a stuck IACV that needs to be replaced.

Here's some other details:
- man to man tranny was also swapped (see address above to see the D15B purchased)...someone mentioned the D15B could have originally been chipped for an auto tranny, but it came to me with the manual.
- shop owner says the harness was replaced during the swap because some lines were cut from the old one when the D16Y8 was pulled out...he also mentioned the harness matched up well, with all the sensors and ecu.

I know there's tons of info on these forums regarding D15B's, i.e., single vs double vs triple stage VTEC's, obd1 vs obd2, P72 ecu vs P08, etc., etc.

I am completely lost :confused:...can someone please help a poor ignorant man figure out what D15B (S/N 2804664) engine he's got and to get it working correctly in this 99 civic ex?
 

Matts96HB

.
Moderator
VIP
since the local shop did the swap, id say you need to take it back to him.

but that isnt likely since youre here asking these questions so ill try and help you out. an obd2>obd1 conversion harness would be necessary for this swap. the wise way to do it would be to run the d15b ECU.

visual inspection of the IACV is fairly easy, just pull it off of the back of the intake mani and take a look at the screen. if its dirty, clean it, that is a typical problem with those. there should be a code somewhere on the ECU, it should be a p08 if it is in fact the correct ECU i believe.
 

dhudge

New Member
Like I said, the shop owner thinks it's a stuck IACV. He says he'll clean it out, but when/if cleaning the IACV has no effect he'll be pushing to replace it, which means mucho $$$.

I'm thinking/wondering if it'll cost less to change out the ecu and wire harness...unless it turns out that I have a 3 stage vtec. I hear the ecu for a 3 stage (P2J-003) is pretty much unobtainable.

Can you tell me how to determine what stage vtec D15B I have?
 

Matts96HB

.
Moderator
VIP
Like I said, the shop owner thinks it's a stuck IACV. He says he'll clean it out, but when/if cleaning the IACV has no effect he'll be pushing to replace it, which means mucho $$$.

I'm thinking/wondering if it'll cost less to change out the ecu and wire harness...unless it turns out that I have a 3 stage vtec. I hear the ecu for a 3 stage (P2J-003) is pretty much unobtainable.

Can you tell me how to determine what stage vtec D15B I have?
simple way to figure out if it is the IACV thats your problem is to start the car and let it idle. unplug the IACV, and see if it changes anything in the cars behavior. if not, the IACV has an issue. if it does, then you know the IACV is not the problem.
 

dhudge

New Member
Sorry...should have been more specific.
As I understand, there's 3 different variants of vtec...
1) power-vtec (single stage)
2) vtec-e (2-stage)
3) 3-stage vtec (a merging of the earlier VTEC-E and power-VTEC variants)

...the (2-solenoid) picture you show, which variant would that one be?
Would you be able to provide a picture of the solenoids for the other two variants?

My civic ex is not here right now for me to verify which solenoid setup it has, but I'll post a pic when it becomes available.
 

dhudge

New Member
Well, I guess I'm too new, with insufficient admin rights, to upload images, but here's a pic of an engine I found on google images that looks very similar to my solenoid setup:
 

dhudge

New Member
simple way to figure out if it is the IACV thats your problem is to start the car and let it idle. unplug the IACV, and see if it changes anything in the cars behavior. if not, the IACV has an issue. if it does, then you know the IACV is not the problem.
Okay Matt, here's an update:
With IACV plugged in, engine does as described before: cycles between 1600-1800 @ ~1 Hz

With IACV unplugged, engine rpm dropped to a steady 1200'ish.

So by yours (& hondafreak's) account, this means the IACV is working, but not properly, i.e., a P08 ecu with with an obd1>obd2 conversion harness should solve the issue, is that correct?

The only thing that bothers me is if the shop used a standard obd2 harness, how all the sensors matched up as they indicated. There's a big difference between the obd1 & 2 harnesses, hence the conversion harness, right?
 

hondafreak513

Well-Known Member
just some different plugs on the engine.. I don't want to say getting the conversion harness will exactly fix it I would try cleaning the IACV or swap it out with another one. Also make sure all the air is out of the coolant lines if there is a air pocket around the IACV it will cause the motor to hunt..
 
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