VX EGR and VTEC solenoid
 

Case: JDM D15Z1 installed in 89 DX

Issue: Hard to adjust idle, engine stalls when vtec engages

FYI: I had a P07, turned out to be bad. Was told by several people that it would run better (the vtec portion that is) with a P28. It has a P28 installed and currently displays no cel. It is running a 5 wire 02 sensor.

1) Any comments on the P28 for the vx engine vs the P07 which alot of people state is a must?

2) This engine did not have the oil pressure switch on the vtec solenoid. Could it be located elsewhere separately? Currently the switch is sort of "bypassed" with a little wiring tweak, the ecu does not throw any codes. Could I just use another d series solenoid with the switch installed and wire up correctly?

3) Currently the egr control system is not hooked up. I have a control box but did not install yet. Is this only an emmission issue or does it affect the performance? If it doesn't need it than is there anything in particular you should do with the egr valve on the engine as it relates to vacuum, etc.?

Any suggestions or comments are greatly appreciated. Hopefully I've given enough of the basics here. Are any of the above my issues with the vtec stalling the engine and idling/timing issues?

Sorry but there are no "JDM" D15Z1. Could you please check the engine block and give us the code from there? should be D15B or could be D15Z7.

Are you jumping the two pin plug under the dash and following the idle adjust procedure?

Are you using an OBD0 to OBD1 Jumper harness?
Is this P28 ECU chipped and running a custom tune on it? If not, it should be throwing a CEL for the 5 wire O2. If it truly is a D15Z1, you will get the best mileage using the P07
The JDM VTEC motors did not use oil pressure switches
I'm confused...first you say there is no oil pressure switch, then you say it's bypassed!?!? Or do you mean the VTEC solenoid is "bypassed"? If the VTEC solenoid is bypassed and not activating and you're running with a P28....the high cam is not kicking on and then the ECU is trying to dump extra fuel into the combustion chamber. This will cause the motor to bog/lose power.
The P28 will not be able to control the EGR Box, but if you get a P07 to run the motor, then yes, you should hook up the control box as it will allow the motor to run properly and give you the best mileage possible.

Get back to us and we can help you work out all the bugs. :thumbup:

*Sorry, it's a D15B. I guess that is supposed to be a JDM direct replacement for the D15Z1, I just call it the same when I've been getting parts that I forget the gory details.

*I am not the one doing the work currently, however it is my understanding that if you want to adjust the timing with the engine running you need to use the pin jump procedure you mentioned, or you could make the adjustment with the engine off and then restart and check...is that correct? I believe the adjustments have been done in the latter.

*To clarify the issue, it seems as though the vtec shuts the engine down during the second cycle of the rpm range.

*I did use an OBD0 to OBD1 jumper harness.

*The P28 is standard. It's my understanding that the 5th wire is a second heater circuit and that the ecu is only looking for one, correct? Right now, it does not throw any cel either at start up or after it is warm.

*My bad on the pressure switch/jump issue. It does not have an oil pressure switch on the vtec solenoid, however the ecu is looking for one. There is no cel now because we have temporarily grounded it thus making the ecu think there is none. Does it need one to function properly? They are cheap enough that I think I will put one on anyway to have it installed properly even though the engine did not come with one...I want my ecu happy!

*I have an egr control box to connect to the egr valve on the engine but I am aware that the P28 will not operate it so it is not installed. Does the egr valve need any special attention here or just leave it as is as long as the P28 is the ecu?

So, I do not know the full extent of the pressure switch function, like if it opens after a higher oil pressure or not so I?m not sure if it is the cause of the engine cut out on the second cycle through the rpm range and no vtec. Outside of the above issues, shouldn't it function normally, albeit perhaps with less efficient fuel economy, without the egr control box, hooking up the solenoid with a pressure switch and keeping the P28? Any ideas? Thanks to all for your help and as usual quick responses.

I concur with TomO - mostly
1) The JDM D15B Vtec-e is the same (for all practical purposes) as the D15Z1 and absolutely needs the P07 ecu to work properly for all the reasons TomO mentioned. Your valve cover does say vtec-e, right?
2) The JDM version didn't have an oil switch, but the P07 wants one. Your best bet would be to find one and install it in place of the plug on the vtec solenoid. I found one on ebay when I needed one. Any vtec oil switch will work, even b motors or preludes, but the solenoid housings are different for the different motors.
3) The egr will help your mileage, hook it up, especially since you have it (only with a P07 though).
Fix all of this before you worry about your idle problem, chances are it will go away when you get the right ecu and hook everything else up. Good luck.

Edit: you beat me to my post! The only thing the oil pressure switch does is prevent vtec engaging when oil pressure is insufficient. Its a safety thing, you don't need it, but there isn't any reason to not use it either. As for the 5 wire O2 sensor, it is completely different than a 1,,3 or 4 wire sensor, not just a second heater. Again, you need a p07 to make it work properly.

^^^:thumbup:
I agree with nowhhs.