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steffen707 · 05-04-2011, 01:13 PM

Quick background before the question-
I just swapped a civic vx motor from a running car, into another hatchback. All the wiring and ecu was double checked. The only wire I have not hooked up yet was the switched power to the black/yellow wire on the egr control box (black box on firewall). The car fired right up on its first try and runs like a top, however....

I drove the car about 10 miles and the check engine light has not come on yet. It comes on briefly when you start the car (normal), but i'm surprised it has not come on due to the egr black box not being hooked up. I unplugged the vtec connector and the check engine light came on right after startup so I know the MIL and ecu check engine circuit are working.

I looked at the honda manual and on 11-34 it trouble shoots MIL code 12. I know some will ask why i was troubleshooting if no code was present, but i'm wondering why its not triggering this code with the egr system effectively disconnected.

I hooked my vacuum gauge to the black box and connected the black/yellow wire to pos bat, and the orange/blue to ground and the gauge does go up to about 8" within 1 second like the manual says it should so I assume the egr black box (if hooked up - remember it doesn't have power to it yet) would function properly. I then connected the vaccum gauge/pump to the egr valvue and with the engine idling supplied 8" of vaccum to the valve and the engine didn't surge or die or stumble like the manual said.

Confused I squeezed the pump more, and more and at about 15" the EGR went POP, the car died. (I think the EGR was stuck from not running for over a year and the extra vacuum finally popped it loose). I restarted the car, fired right up. Started to squeeze the vacuum pump and instantly I noticed the car stumbling and having a rough idle (like the manual said it should). I supplied 8" to it and it held that vacuum (like the manual said it should) and it ran rough. Took vacuum away, idle stabilized and ran smoothly. Supplied vacuum to the EGR, ran rough again.

I havn't gone through to trouble shoot all the other things that the manual says should happen, I.E. voltage between wires, and continuity with wires, ect. But I'm fairly certain my wiring is just (except for the one switched positive to the egr black box) My next test was to put a T in between the black box and EGR valve and a vacuum gauge, and hook up the positive to the black box, and drive around and see if the black box does operate the EGR valve.

So now i'm kinda confused. If the EGR black box wasn't hooked up, and the EGR valve was stuck closed, why wouldn't the ECU throw a code? Some people would argue, "DUDE! Just hook up that switched positive to the egr black box and forget about it!" But if the system isn't operating normally and not causing a check engine light, will it operate normally when i do hook it up correctly? Isn't the EGR an essential part of the whole lean burn d15z1 swirl combustion high gas mileage motor? If its not working right I wont get super gas mileage.

Can anybody shed some light on this for me?

05-04-2011, 01:13 PM	#1 (permalink)
steffen707 Master EcoModder Join Date: Oct 2009 Location: Midwest Posts: 337 Thanks: 4 Thanked 37 Times in 21 Posts	Civic VX EGR troubles Quick background before the question- I just swapped a civic vx motor from a running car, into another hatchback. All the wiring and ecu was double checked. The only wire I have not hooked up yet was the switched power to the black/yellow wire on the egr control box (black box on firewall). The car fired right up on its first try and runs like a top, however.... I drove the car about 10 miles and the check engine light has not come on yet. It comes on briefly when you start the car (normal), but i'm surprised it has not come on due to the egr black box not being hooked up. I unplugged the vtec connector and the check engine light came on right after startup so I know the MIL and ecu check engine circuit are working. I looked at the honda manual and on 11-34 it trouble shoots MIL code 12. I know some will ask why i was troubleshooting if no code was present, but i'm wondering why its not triggering this code with the egr system effectively disconnected. I hooked my vacuum gauge to the black box and connected the black/yellow wire to pos bat, and the orange/blue to ground and the gauge does go up to about 8" within 1 second like the manual says it should so I assume the egr black box (if hooked up - remember it doesn't have power to it yet) would function properly. I then connected the vaccum gauge/pump to the egr valvue and with the engine idling supplied 8" of vaccum to the valve and the engine didn't surge or die or stumble like the manual said. Confused I squeezed the pump more, and more and at about 15" the EGR went POP, the car died. (I think the EGR was stuck from not running for over a year and the extra vacuum finally popped it loose). I restarted the car, fired right up. Started to squeeze the vacuum pump and instantly I noticed the car stumbling and having a rough idle (like the manual said it should). I supplied 8" to it and it held that vacuum (like the manual said it should) and it ran rough. Took vacuum away, idle stabilized and ran smoothly. Supplied vacuum to the EGR, ran rough again. I havn't gone through to trouble shoot all the other things that the manual says should happen, I.E. voltage between wires, and continuity with wires, ect. But I'm fairly certain my wiring is just (except for the one switched positive to the egr black box) My next test was to put a T in between the black box and EGR valve and a vacuum gauge, and hook up the positive to the black box, and drive around and see if the black box does operate the EGR valve. So now i'm kinda confused. If the EGR black box wasn't hooked up, and the EGR valve was stuck closed, why wouldn't the ECU throw a code? Some people would argue, "DUDE! Just hook up that switched positive to the egr black box and forget about it!" But if the system isn't operating normally and not causing a check engine light, will it operate normally when i do hook it up correctly? Isn't the EGR an essential part of the whole lean burn d15z1 swirl combustion high gas mileage motor? If its not working right I wont get super gas mileage. Can anybody shed some light on this for me?