Civic VX EGR troubles

[steffen707]

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?

[TomO]

It's possible that you haven't yet reached the driving conditions that would require EGR therefore not triggering your MIL. But remember that this is an OBD1 ECU, it would take quite some time, if at all, to trip the MIL for a trouble code related to the EGR not being open enough or open too much (from the sensor on top of it).

Honda might have some very wide specs as to what triggers EGR codes. I know that in the OBD2 ECUs the spec is a lot tighter, along with the OS specs in an OBD2 ECU.

[steffen707]

Fair enough! I will try driving the car farther. I did notice that after driving about 10 miles and then going to my friends house and feeling the lower radiator hose, it wasn't hot. It snowed in wisconsin yesterday morning so its fairly cool out and maybe it didn't even get to operating temp. I then let it sit idling for about 10 more mins, the thermostat kicked open and the lower radiator hose got hot, and then finally the radiator fan came on.

I think i'm going to hook up that switched positive wire, and plump a vacuum gauge inbetween the egr control box and the egr valve and just monitor if its actually getting vacuum.

If the EGR system in my car for some reason isn't working right, due to an ecu error or something else, would this cause poor gas mileage?

[steffen707]

Also, does lean burn also take a long time to start working? Or does that basically start working right away? I noticed VTEC was working relatively fast from engine stone cold to driving for only a few minutes. Maybe the 12v/16v operation of vtec-e doesn't require the car to be warmed up as much as say vtec on a B16 engine.

[brucepick]

Hmm. You probably know this better than me but - - -
Usually the lower rad hose is post-cooling and isn't very hot. Unless the car has been sitting idling in warm weather. If it's truly hot the fan better come on, quick.

Upper hose is the one I check to see that the engine is warming up and t'stat is opening.

If you have a digital temp gauge I'd consider some grill block. I add/remove grill block so the gauge settles in around 182º F. That's where it seems to stabilize if it gets enough cooling air, but not too much. Other temps result if I choke off too much cooling air, or if I let too much blast through in winter. On a Gen-6 Civic. I suspect yours is same or similar for temperature.

[steffen707]

Originally Posted by brucepick

Hmm. You probably know this better than me but - - -
Usually the lower rad hose is post-cooling and isn't very hot. Unless the car has been sitting idling in warm weather. If it's truly hot the fan better come on, quick.

Upper hose is the one I check to see that the engine is warming up and t'stat is opening.

If you have a digital temp gauge I'd consider some grill block. I add/remove grill block so the gauge settles in around 182º F. That's where it seems to stabilize if it gets enough cooling air, but not too much. Other temps result if I choke off too much cooling air, or if I let too much blast through in winter. On a Gen-6 Civic. I suspect yours is same or similar for temperature.

its a 97 civic hatch, havn't messed with grill block before. Going to be somthing i will definately try once i get this vx engine running tip top to compare gas mileage change with other mods. nothing radical like aerocivic, but just some things to squeeze a bit more mpg out.
The radiator fan kicked on very soon after the tstat opened and the bottom radiator became quite hot. I don't have a laser temp gun, but thinking about getting one just for kicks. might help out with autox and reading tire temps to figure out suspension changes between runs.

[TomO]

Originally Posted by steffen707

Also, does lean burn also take a long time to start working? Or does that basically start working right away? I noticed VTEC was working relatively fast from engine stone cold to driving for only a few minutes. Maybe the 12v/16v operation of vtec-e doesn't require the car to be warmed up as much as say vtec on a B16 engine.

The VTEC-E crossover will work right away on the D15Z1 motor since it only brings the motor up to 16v mode. The regular VTEC Honda motors need to have coolant temps up over 140*F and other variables met before VTEC will engage.

Lean burn will start to function once certain coolant temps, throttle positions, RPM conditions, and vacuum conditions are met. Basically though, once the car gets above 140-160*F the ECU will start to lean out the mixture as long as vacuum is held at 6in/hg or more.

[steffen707]

My EGR control solenoid is still effectively unplugged.

I drove the car around town today long enough to go to advanceauto, leave it running, buy a new car battery. Go to the coin pay car wash, leave it running as well, then drive about 3miles to the highway and drive 18 miles on the highway and the check engine light never came on. This took about 45 minutes.

I'm shocked the EGR not being hooked up didn't throw a code, and i'm wondering WTF? I'm hooking up my vacuum gauge to the EGR valve line and then hooking up that switched positive wire for the EGR control valve and we'll see what happens I guess.

[steffen707]

I think i may have posted this in another thread, but I i tested the EGR control valve and with 12 volts it does provide vacuum, also with a vacuum pump to the EGR and car idling it will run rough like it should.

Putting it all together and have driven it about 100 miles for testing cruise and other stuff on the car and going to work for a week, and the egr still doesn't appear to be working, nor getting a check engine light, and I got between 45-50mpg on my 100 mile fill-up.

I guess i'm just going to not worry about it for now. Oh, i also substituted another federal VX ecu, and nothing changed. I've got a 3rd federal one I might try, but i suspct no changes with that as well.