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Discussion Starter #1
I am having serious problems with my D15b to the point where I just wanna give up on this car. Here is the run down. I have a 94 vx hatchback that i swapped a "JDM D15b" into. And at first the car didn't want to start but I finally got it to, then its didn't want to pass 4000rpm and i figured out that it was the wrong cable going to the IACV so now that all good. But now since I fixed that I have other PROBLEMS!!!! BTW the ECU running the car is a virgin P28.

1. When i start my car up from a cold start it revs all the way up to 4000rpms and then works its way down to a consistent idle of 1500rpms. I do have a CEL light and the codes are:
Code 7 Throttle position sensor
Code 10 Intake air temperature sensor
Code 41 Heated oxygen sensor heater
And I dont know if any of these codes would effect my car idling all [email protected]&$%d up or keep it from idling correctly and not at 1500rpm. Any help would be appreciated

2.My car has no power until about 2000-2500rpms. Like it starts of struggling and once it hits 2000rpms its like a burst of power. I have new spark plugs, new wires, and a new dizzy so idk what could be causing these problems. any help would be appreciated.

3.I have been reading that the redline for a JDM D15b is 7500rpms. Well my mines doest go past 5500rpms. It get there and thats it. Could it be the tranny or something?

4.How do you know if its a D15b? It says it on the block but how do i know its not a D15b7? Yes it has a V-tec solenoid and jank but this motor runs like shit!!! Also I dont think V-tec even works.....

5.Found oil on the top of my tranny by the speed sensor any idea of where this might be coming from and also my speedometer doesnt work... Thanks

PLEASE ANY HELP WOULD BE APPRECIATED and below are videos of what my car is doing.

4000rpm start up

1500rpm idle

5500rpm redline
 

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92 Civic Hatch
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1,757 Posts
Have you ever, EVER, worked on a car before?

Did the 94's even have an IAT sensor?
 

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VTEC withdrawals
i "ride" yo momma
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1,339 Posts
have you swapped ecus to make sure the one you have is good? i forget which one goes with that motor...which is sad since i have that one.

on the b7 thing
it wont have the 7. thats the only real way to tell. block should just say d15b
 

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VTEC withdrawals
i "ride" yo momma
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1,339 Posts
and honestly...fix the codes and then come back lol. id swap TB's to check the tps
 

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Did you swap the wires for the o2 sensor?? The vx model uses a 5 wire o2 where the d15b uses a 4 o2 sensor.

Do you have the right plugs plugged in for the tips and iat?
 

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Formally D_Tuned
97 civic HX
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2,884 Posts
Check for vacuum leaks at the intake manifold gasket and other obvious places.

A p28 is not ideal for that engine ( Unless its chipped with a p08 map ) It will run but my very first honda swap was a 3 stage and with a OEM p28 it ran quite poorly.

You mentioned a new distributor, when installing this did you set the timing with a timing light afterwards?

Edit: also fix the obvious, iat, tps, and you can fix the o2 or disable it with a chipped ecu.
 

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VTEC withdrawals
i "ride" yo momma
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1,339 Posts
Did you swap the wires for the o2 sensor?? The vx model uses a 5 wire o2 where the d15b uses a 4 o2 sensor.

Do you have the right plugs plugged in for the tips and iat?
my d15b came with a 1 wire...

Check for vacuum leaks at the intake manifold gasket and other obvious places.

A p28 is not ideal for that engine ( Unless its chipped with a p08 map ) It will run but my very first honda swap was a 3 stage and with a OEM p28 it ran quite poorly.

You mentioned a new distributor, when installing this did you set the timing with a timing light afterwards?

Edit: also fix the obvious, iat, tps, and you can fix the o2 or disable it with a chipped ecu.
i feel like a moron for not mentioning the dizzy part.
 

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my d15b came with a 1 wire...li
Good to know but,He still needs to convert to a 4 wire o2 for the p28 ecu. If not all ready done.
 

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EG8
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1,055 Posts
What intake manifold are you using? Did you swap it in, or was it originally with the car?

I would do these things in this order:
-timing with light
-test TPS(should be 0.5v close and 5v WOT I believe)
-fix IAT sensor(white plug, should have green/red wires going to it)
-check vacuum leaks
-check throttle cable tension(needs play)
-check throttle stop screw(should not need to adjust this)
-clean/adjust FIV (I think you need to screw it in to drop the idle to around 1500)
-while test connection is jumped, unplug IACV and check base RPM(adjust to 570-670rpm)
-plug in IACV, pull fuse to rest ECU with car off.

This should help with the idling issue at least.
 

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97 civic lx
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967 Posts
Did the 94's even have an IAT sensor?
None of the ones I've worked on.


Get a 4 wire o2 sensor from your local parts store or junk yard to start off with. I'm assuming the car previously had a z6 in it. So get a 92-95 civic ex o2 sensor.

As for the sluggish feeling, check mechanical timing. Along with electrical timing.

And for the stupid low redline, unplug your negative ground cable for a few minute, then reconnect it. Ecu is probably just in limp mode from all the codes your throwing
 

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Discussion Starter #11
Have you ever, EVER, worked on a car before?

Did the 94's even have an IAT sensor?
I have worked on cars a little but what I dont understand I google.... And also I dont believe it did come with a IAT sensor. Now from what I see on my harness. I have a little needle thing that is suppose to go into my intake and thats suppose to read the air temp (what my friend said) but i dont have a spot on my intake for this.... Could that be the IAT and is there a way to bypass this? Will post a pic of the needle thing later.
 

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Discussion Starter #12
have you swapped ecus to make sure the one you have is good? i forget which one goes with that motor...which is sad since i have that one.

on the b7 thing
it wont have the 7. thats the only real way to tell. block should just say d15b
I have another ECU a chipped P28 and they both do the same thing but the chipped P28 have a D16z6 map on it which I was told should have a P08 map on it.

And thanks it says D15b.
 

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92 civic cx hatch
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1,012 Posts
D15b code 10! Intake Air Temp Sensor! Need Help!

scroll down i am guessing that with that sensor unplugged and not hooked up into the intake manifold is were your vacuum leak is coming from because it seems to be a big leak and with the ecu knot knowing how cold the air coming into the motor is can be causing the sluggish feel
 

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93 Civic del Sol Si
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1,278 Posts
This is kind of a dumb question, but do you have coolant in your system? If so did you bleed it? When I swapped heads on my b7 it did idle that high until it warmed up enough to push coolant into the IACV. If there is a big air bubble in the IACV it will idle that high until it is full of coolant... Just trying to cover basics.
 

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Discussion Starter #16
Did you swap the wires for the o2 sensor?? The vx model uses a 5 wire o2 where the d15b uses a 4 o2 sensor.

Do you have the right plugs plugged in for the tips and iat?
I am going to get a new o2 wire and also I have to check when i get home if the right wires are plugged into the TIPS and IAT
 

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Discussion Starter #17
Check for vacuum leaks at the intake manifold gasket and other obvious places.

A p28 is not ideal for that engine ( Unless its chipped with a p08 map ) It will run but my very first honda swap was a 3 stage and with a OEM p28 it ran quite poorly.

You mentioned a new distributor, when installing this did you set the timing with a timing light afterwards?

Edit: also fix the obvious, iat, tps, and you can fix the o2 or disable it with a chipped ecu.
It has no leaks but I will check again.

And I have a chipped p28 that I am going to have a friend put a p08 map on for me to see how that runs.

I dont think that 94 came with IAT but I will post a pic of something my friend is saying is the IAT sensor. And I will fix other areas. Thanks
 

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Discussion Starter #18
What intake manifold are you using? Did you swap it in, or was it originally with the car?

I would do these things in this order:
-timing with light
-test TPS(should be 0.5v close and 5v WOT I believe)
-fix IAT sensor(white plug, should have green/red wires going to it)
-check vacuum leaks
-check throttle cable tension(needs play)
-check throttle stop screw(should not need to adjust this)
-clean/adjust FIV (I think you need to screw it in to drop the idle to around 1500)
-while test connection is jumped, unplug IACV and check base RPM(adjust to 570-670rpm)
-plug in IACV, pull fuse to rest ECU with car off.

This should help with the idling issue at least.
-I am not sure how to do timing with light but I will take it to a shop that can check that out.
-As far as the IAT I dont think my car has one. I have a white needle sensor that my friend says is the IAT but this sensors needs to get plugged into the intake and my intake doesnt have a spot for it. Plus I am not sure that even the IAT I will post pics when I get home.
-What and where is the FIV?
And sorry you lost me on the last 2 things you complete lost me on... But I will try to figure out what your talking about.
Thanks for your help.
 

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Discussion Starter #19
UPDATE!!!! I should have mentioned this... I was reading this and it says "obd1 had it built into the intake manifold, obd2 cars had it built into the intake arm.....so if your running a obd2 intake on a obd1 motor without the sensor in the intake, your not running a iat sensor thus throwing the code".... This is talking about the IAT... I have a y8 manifold on my D15b which would mean the senor would have to go into the intake arm which is the white little senor I was talking about (I will still post pics up of it to make sure)

And the say to fix the problem is "you just need the sensor and just jb weld it into your intake for a cheap fix or buy the aluminum flange and have it welded on for a cleaner look. my opinion would be to buy a z6 intake manifold, its a cleaner look having the iat on the back of the mani hidden, there dirt cheap and you will see a deffinate improvment in performance"

Do I have to so this or can I bypass this somehow. Also does a y8 manifold even have a IAT on the back of it like a z6 manifold does?
 

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the y8 iat is in the air intake pipe near the throttle body. the z6 is on the back of the intake manifold...

z6 iat..

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