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Discussion Starter #1
95 Civic D16Z6

I have an intermittent problem ever since I replaced my O2 sensor. Every now and then I just lose all power. I can floor it but the engine just stays bogged down until I get to about 4th gear(sometimes) and it just magically kicks back up(you can feel it push you back a bit) and the issue disappears. If I'm rolling along I can turn the car off and turn it back on and the issue seems to go away as well. The CEL came on once but that's it.

I'm not sure what it could be. Like I said the O2 sensor is brand new(Denso). The spark plugs are new-ish Denso plugs, cap and rotor recent as well as the distributor, and new NGK wires. Fuel pump is a new Walbro, fuel pressure is about 44psi. Injectors are stock.

So could it be the O2 sensor?
 

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95 Civic D16Z6

I have an intermittent problem ever since I replaced my O2 sensor. Every now and then I just lose all power. I can floor it but the engine just stays bogged down until I get to about 4th gear(sometimes) and it just magically kicks back up(you can feel it push you back a bit) and the issue disappears. If I'm rolling along I can turn the car off and turn it back on and the issue seems to go away as well. The CEL came on once but that's it.

I'm not sure what it could be. Like I said the O2 sensor is brand new(Denso). The spark plugs are new-ish Denso plugs, cap and rotor recent as well as the distributor, and new NGK wires. Fuel pump is a new Walbro, fuel pressure is about 44psi. Injectors are stock.

So could it be the O2 sensor?
ether bad o2 or coincidence. o2 was replaced because?
 

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At WOT the oxygen sensor does not come into play as the ECU goes into open loop.

If you do not have a wideband installed, back probe your o2 sensor signal wire and get a voltage read out at WOT. Should be around .900-.950v. chances are even though your pressure is set at 44PSi (need to know if vacuum on or off), you are overrichening your AF with the walbro pump (if it's a 255HP). When the vacuum is removed from your fuel pressure regulator it should increase by appx 10 PSI. Chances are with the Walbro it's gonna be higher than than when going WOT since that removes intake vacuum to your regulator.
 

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... The CEL came on once but that's it. ...

IMO, I would start with something that you know. You had a CEL. If you haven't pulled the 'hazard' fuse or unplugged the battery, then jumper your harness connector and see which code it's flashing. Go from there.

As far as fuel pressure is concerned, another way to tell if you're running ridiculously rich is to pull your plugs, and just inspect them the old fashioned way. Thick black-ish carbon buildup = super rich. Even though I doubt that's the problem, as I would think the hesitation would be more consistent if your plugs were fouled out by a rich a/f mixture.

Let us know what you find.
 

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Discussion Starter #5
At WOT the oxygen sensor does not come into play as the ECU goes into open loop.

If you do not have a wideband installed, back probe your o2 sensor signal wire and get a voltage read out at WOT. Should be around .900-.950v. chances are even though your pressure is set at 44PSi (need to know if vacuum on or off), you are overrichening your AF with the walbro pump (if it's a 255HP). When the vacuum is removed from your fuel pressure regulator it should increase by appx 10 PSI. Chances are with the Walbro it's gonna be higher than than when going WOT since that removes intake vacuum to your regulator.
It's 44psi at idle with everything hooked up. So with vacuum.
 

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Discussion Starter #6
ether bad o2 or coincidence. o2 was replaced because?
O2 replaced because the other one was nearly destroyed from road rash due to bad placement when installing exhaust. Besides, it was almost 7 years old anyway.

Anyhow, another symptom I've noticed since this started is if I suddenly let go of the accelerator when slowing down the engine dies completely.
 

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hows your cap and rotor? check that ground on the thermostat housing as well and clean it. I remember once mine looked ok but I put a wire brush bit to it and cleaned it and the motor started right up after being parked for a week of night figuring it out....
 

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Discussion Starter #11
actually the fuel psi for a z6 is 40 with vac line connected.
That's what I thought.

The Denso O2 was hitting on the damn power steering rack and the wires were exposed from the rubbing so I replaced it with an extra NTK I had(which is actually shorter) and implemented a fix for the clearance. I crank it up and it runs fine for about 10 seconds then the idle screws up and I get a CEL. Now it's running even worse.

So the CEL it was giving is a "4". Crank position sensor. So I scoured the net to find some resources on that. I did the distributor test. Tested the B and F pins on the harness, resistance was about 460. No continuity to the ground. So I plugged that back up. Next, it says to test for resistance at the B15 and B16 pins on the ECU harness. I did that, no resistance. So that's a bad thing and I don't know how to fix it.

PICS:
Denso O2: https://dl.dropboxusercontent.com/u/100029881/2013-07-30 18.29.44.jpg

O2 Fix(yes I just did that): https://dl.dropboxusercontent.com/u/100029881/2013-07-30 18.30.03.jpg

Spark plugs: https://dl.dropboxusercontent.com/u/100029881/IMAG0256.jpg
 

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That's what I thought.


So the CEL it was giving is a "4". Crank position sensor. So I scoured the net to find some resources on that. I did the distributor test. Tested the B and F pins on the harness, resistance was about 460. No continuity to the ground. So I plugged that back up. Next, it says to test for resistance at the B15 and B16 pins on the ECU harness. I did that, no resistance. So that's a bad thing and I don't know how to fix it.
You can download a factory service manual on the webz for free. It'll explain how to trouble shoot the code.
 

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Discussion Starter #14
Like I said I followed the service manual steps up until where you unplug the ecu harness and test that but I don't get a resistance reading between the b15 and b16 pins.
 

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hows your cap and rotor? check that ground on the thermostat housing as well and clean it. I remember once mine looked ok but I put a wire brush bit to it and cleaned it and the motor started right up after being parked for a week of night figuring it out....
Props to both you guys. I got a chance to pull the distributor off and lo and behold, chaos inside. I don't know how my car was running at all.

DISTRIBUTOR 1
DISTRIBUTOR 2
DISTRIBUTOR CAP

You can see several screws on the inside assembly came loose and were just sitting there. The rotor button was loose. The bearings on the shaft are gone I suppose because there is oil in there. Deep cuts on the cap probably from the shaft being loose. I don't understand why this keeps happening to me. I have to replace distributors at least once a year!!

Well anyways I replaced that and it starts right up now, the starter barely has a chance to do anything, it's that quick. However, even after removing the ECU fuse to reset the code I'm still getting a CEL 4 when I put the jumper in.
 

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well, probably a wire or ecu problem since this is the 2nd dizzy, but with a re-man its possible.

what does the fsm say is wrong according to your tests?
 
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