MD207

To start off I'd like to say: 1. First time on these forums 2. I know very basic mechanical work. (my brother is the mechanic not me ) So I may have posted in the wrong forum and may be hard to work with.

I have a 97 civic LX with 171k miles, D16y7 I believe. Daily driver nothing spectacular.

I have some no name 4-2-1 header because the stock one was cracked and the o2 goes into the lower end of where 2 connect right before it connects to the other 2.

The spark plugs/wires/dist were changed about 50k ago but I checked and they seem to show my car is running rich.

The car stutters sometime right on start up and other times about 20 seconds down the road. If I don't floor it; it basically keeps doing it the whole time. When I do floor it and keep above 3000 for a bit of time; it stops all together, but the rpms slightly drop - go up - drop - go up for a little bit.

I think it may be the primary o2 but don't want to rule out anything else, and want to be somewhat certain before I start changing a bunch of things.

Any questions feel free to ask. Again sorry if I'm in the wrong forum or hard to work with

Tested
MAP
O2

Replaced
Dist. Rotor
Dist. Cap
Spark Plugs
O2

Needs checked
IACV (seems to work normally but may need cleaned)
EGR
Ignition Coil


Solution
Primary O2

NotARaCist

iTrader: (1)

Don't worry, you're in the right forum, and for a first post, you did fine

Is the CEL on? Does it work? If it is on, what codes are thrown? https://honda-tech.com/honda-civic-d...lists-1901557/

MD207

CEL isn't on forgot to add that.

I haven't been able to check codes which im hoping to do tomorrow, but a while back my wiring harness (i think) shorted out and my god is that a fun puzzle. Anyway it threw tons of codes and we weren't sure what was right or wrong and I haven't checked since then.

MD207

No codes are being thrown.

Not sure if this matters but I thought o2's put out between .1 & .9 (not sure):
At idle the primary o2 is running voltages at high end 1.--v's and low end 2.--v's.
At idle the secondary o2 is running ~0.80v

The secondary however is in the wrong spot and I haven't gotten the chance to move it.
It is before the cat instead of after.

MD207

Anybody know? Been searching but most posts I've seen about this just end with no answer. Except one that was primary o2.

NotARaCist

iTrader: (1)

If I can remember, I'll check my FSM when I get home to give you O2 testing specs. Alternatively, you could download the FSM and check it.

MD207

Found one and the testing is on page 11-140 and a ton more further on, so I'm not sure I'm in the right place.

Check for a short in the HO2S:
1. Turn the ignition switch OFF.
2. Disconnect the Primary HO2S
(Sensor 1) 4P connector.
3. Start the engine and let it idle.
4. Check the Primary HO2S
(Sensor 1)output voltage with
the scan tool


Does it stay at 0.1 V or less? If no Replace HO2S.

Mine was around 2.00V but it was not disconnected. However I still think I'm looking in the wrong spot.

Edit: My bad this is depending on codes, need to find just the regular info on normal O2 stats first.

MD207

Think it's normal. For the short time checking it; It started at around 1.8 and jumped to low 2's and was around 2.5v a bit.

"Reference voltage supply. With fully warmed up engine at idle: about 2.6-2.8v"

It wasn't too far off i suppose.

NotARaCist

iTrader: (1)

You might be. I'm off work in ~3 hours, I'll try to remember to check my FSM when I get home and post some relevant pages for you (unless RonJ beats me to it).

MD207

Okay. Thanks a lot! I work a lot Tuesdays-Thursdays but I'll try to check in each day. I might try'n check my MAP sensor sometime tomorrow but might not get the time.

MD207

Just realized that my Primary O2 sensor goes into only 1 pipe on my header. A little bit before it even gets to the 4-2 spot. Seems like a bad spot? Can't even remember when it started happening but could it possibly be due to bad O2 sensor placement?

NotARaCist

iTrader: (1)

Unlikely. It's suboptimal, but not bad enough to cause the issues you're having.

While we're poking at things, have you checked your ignition timing?

MD207

No I haven't. I'll look into doing it within the next couple of days.

NotARaCist

iTrader: (1)

I know you said you aren't getting any codes, but just run through these tests and make sure the numbers are all within range. Also, just to be sure, when you turn your key to ON(II), your CEL does come on for ~2 seconds, then turn off, right?

MD207

Actually wasn't sure about the CEL but on my lunch break I checked and it works on start up.

I also saw resetting the ecu is the first step on testing, and although I can't test right now; I did it anyway just to see if it noticeably changes anything. Won't be leaving for 5 hours though so won't know till then.

NotARaCist

iTrader: (1)

The "reset the ECU" part of testing is to see if the code returns, to determine if it's an intermittent or recurring problem. Since you're CEL isn't on and we're trying to nitpick things at this point, you can skip that step.

MD207

Didn't expect it to do anything but doesn't hurt to try. I probably can't test till thursday but should be able to do something thursday-monday.

Thanks for all the help & suggestions. I'll keep getting back to you with updates/question.

Also wondering if when a while back my wiring harness was rubbing and shorted out (fuse 15 blowing problem) that it might have messed something up?

MeatballLX

I had a similar issue, although mine gave codes.
After putting my trans back in, i mistakenly switched my 02 sensor plugs (ie plugged sensor 1 into where sensor 2 goes in the harness and vise versa). It gave the same symptoms you are describing when I drove it (felt like a bog/buck). After I switched them, everything worked as normal. Maybe try to switch them.

Edit: Mine is a 2000 LX with the d16y7 just like yours. maybe post a picture of that part of the harness if you dont feel like switching them.

MD207

The o2's are hooked up right. Waiting to get off work to get some testing done today through this weekend.

So far I have these on my list:

MAP Sensor
O2 Sensor
IACV

MD207

Testing

Map sensor:

Voltage: I tested incoming voltage for 5v from each of the side prongs and got 4.97 & 3.55

Continuity: N/A (The voltmeter I used didn't have cont. for some reason)

Sensor Test: The sensor showed 2.8v. When blowing into it; the voltage went up.

(Also it appeared that the sensor had oil on the end of it.. I assume that's not good)

Primary O2 Sensor:
(I forgot to take my printed FMS papers to test it fully but I'm going right after this update to test it)

I used a Snap On Solus Tester (I believe)

Volts on start up : Mid to High 2.--V

I revved the car and it started bogging.

Volts after bogging: .7 - .9

MD207

So unless I messed up the o2 testing I got this. Which makes sense since I had an issue with my harness shorting before.



I noticed when I revved the car up it would drop to near 0 rpm then go back up a tiny bit. Over and Over it worked the same way.

However, my brother looked at it and unplugged and replugged in a bunch of stuff (with the car running... CEL is now on with tons of codes lol) and it was pretty weird.. I drove it to my house and when I revved it to 1500 in park it sounded as if it was idling at 1500 but if i revved higher it didn't. Then I drove again and it didn't seem to bog and I tried to do the 1500 idle thing again when I got home and it stopped doing it.

Im gonna see what it does driving over the next few days and leave updates. It's acting weird now but may have been just a loose wire somewhere.

MD207

It does still bog. Still need to check the iacv

MD207

Not sure when I'll be able to get it back on the lift to check if there is still an exposed piece of wire shorting on the intake bracket, but i'm kind of confused as to why its idling so low out of nowhere.. at like 100rpms. Also if I put it in neutral and just coast down a hill it sits around 500rpm where I could have sworn it used to either sit at 1k or 1.5k.

sonicjoose

Hey OP just recently had a similar issue with a 1998 Honda civic DX

It almost felt like I had a dead spot in my gas pedal, while under low throttle the car would feel like it was misfiring, but if I pressed down on it hard enough the car would perform like normal. Does this resemble what you are dealing with?

I may have the solution

MD207

It sounds pretty much exact. It starts going fine, then out of nowhere starts bogging and the throttle does nothing it will sound like its backfiring (pop pop pop) or will just stop and make no noise at a certain level.

However if I pretty much floor it; it will stop.