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.

No CEL or codes being thrown.

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 anyway 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.

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

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



Solution
Primary O2

 

My first guess is the IACV. If you remove it and clean it with a tooth brush and brake clean the problem is usually solved. Another thing i do when my Hondas have idle issues, is to spray carb cleaner all around the intake manifold and throttle body. If the idle changes, you know you have a Vacuum leak.

 

Okay thanks. I was gonna try'n check the MAP Sensor and primary o2 after I get off work on thursday and I'll try to check that anywhere from thursday to monday. Been to a couple forums with suggestions here and there and it's really helping to get the troubleshooting started. I'll see what I can do over this weekend and check back. Thank you.

 

No Problem! Good luck. Always remember the acronym "KISS" (Keep it simple stupid) While working on cars, It will save you a lot of time and money.

 

I haven't gotten to the IACV yet, but have checked these so far.

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

 

What is your TPS reading?

 

Can't remember and I'm not sure when I'll be able to check. (Hopefully Friday) Can only test Friday - Mondays. :/ My brother was unplugging everything and plugging it back in and most of it seemed to show a reaction. (IACV - idled harder. Stuff like that) Can't recall the tps though. I will have to check. Will also clean the IACV on Friday if I can.

 

Couldn't get into the garage this weekend. Bleh. Might just end up buying a few things without testing. I'm sure it doesn't hurt to replace some things even if that isn't it.

 

Haha just not enough hours in the day!

 

I was told by a guy with a 98 that this happened to him and it was his ignition coil. I had a problem with mine about a year ago and replaced it, but I still want to test it.

Fuel filter, dist cap, rotor coming in tomorrow. Coil seems easy to test so i think I'll just test it before I go replacing it since it's fairly new. Can't remember where I put my meter.. Hoping to get into the garage soon. Feel like I'm taking too long to do this.