Help Please: O2 Sensors, Error Codes, Check Engine Light

[JasonH]

So I've been noticing that my car seems to be sluggish lately. I think it's been getting a little worse, as not only does it seem to take more throttle to accelerate (almost like I'm towing something heavy) but a couple times now at steady speeds of 50-65mph in fifth I got the "check engine" light and the car started stuttering. It doesn't really slow down, but adding more gas doesn't help nor make the car accelerate. Nothing else is strange about the car, no smoke from the exhaust, no funny smells, even my idle is pretty much normal.

So, I pulled the codes and got:
17: LHO2S inversion error
24: RHO2S inversion error

I figure it's not both O2 sensors going bad at once, nor is it a single cylinder (fuel or spark) since it's a problem shared by both banks.

I checked the plastic intake for leaks and found none. Maybe six months ago I had pulled the intake manifold and replaced valve cover gaskets. I also added the Outlaw spacers at the same time. I had no problems with them since so I don't think it's related.

A changed the fuel filter (something I've been putting off for a few months) and reset the computer (I had the battery out when changing the filter.) I took it for a quick test run and it seems to be ok. Accelerating from stop to 60mph is much better than before, and I know longer feel bogged down. I guess the real test will be some longer tests (to work, etc.) with constant speeds.

So, my questions are:
Do you think the fuel filter could have been the problem?
If the symptoms reappear, what should I try next?

Thanks,
Jason

[Mradio]

Jason, I would just change the O2 sensors. I had the same two codes coming up every once in a while, changed both of them and now it's all fine.

[JasonH]

Originally posted by Vlad:
Jason, I would just change the O2 sensors. I had the same two codes coming up every once in a while, changed both of them and now it's all fine.

Huh, that's strange. I guess one could go bad and maybe you wouldn't notice it and not get a check engine light, but then when the second one goes it starts running bad. That seems more likely than both going at once.

Maybe I'll drive it for a little while and see what I think, meanwhile I'll shop around for O2 sensors.

Thanks for the info.

[mxer4eva]

Hey,

Let me give you a cost savings tip, convert to a single wire o2 sensor you can pick one up for maybe $18 or so. Here is a little write up to help you out after you get the sensor. I copied this off probetalk, I dont remember what the posters name was, but I know a lot of you are on probetalk and if you know who wrote this let me know so I can give him his proper credit.

Write up: You don't want to look at the wires on the existing O2 sensor harness for color codes.

What you want to look at is the connector on the vehicle harness. Wire you want is the O2 sensor ECU input wire. The right O2 sensor input wire is Black/Yellow (that is black with a yellow stripe), and the left O2 sensor input wire is Blue/White.

What I would do.. is pull the old (bad) O2 sensor off the car, and cut the wires so you have the old sensor connector and as much of the wiring on it as possible. Then either buy a Universal one wire O2 sensor (comes with it's own crip connector and heat shrink tubing), or you could get a O2 sensor for a 84 caprice... I believe they are cheaper but you'll need your own crimp connector or my favorite solder and heat shrink.

After you get the new O2 sensor and have the cut off harness from the old O2 sensor what you want to do is identify which wire on the old sensor's harness is the one that you want to connect to the new sensor's single output. To do this you want to match up the wiring on the connector to the wire colors from the harness on the car, that way you'll be certain to get the appropriate wire regardless of who manufactured the old O2 sensor (different manufacturers use different colors for the sensor output). After you've found the appropriate wire, connect that to the new sensor output by stripping the two wire ends and either soldering them or crimping them together. The other three wires can either be removed from the connector (a little tricky but recommended) or you can cut them short and tap them off. It is important to isolate each wire seperately, because two of them are the heater wires and are connected to the main power relay to the ECU; shorting them will blow a fuse and the car will not run. Then tape it all up, put the sensor in, and plug it into the harness.

What I did with mine is I tapped a wire into the O2 sensor and ran it up near the battery. That way I could check the O2 sensor voltage to make sure it varies. I checked it again yesterday and from a cold start it takes about 30 seconds for the O2 sensors to start responding (mind you this is the one wire sensors that I bought new, and they are not heated). By responding I mean they show approximately .3-.4 volts at idle, and when I manually revved the engine by hand actuating the TB valve, the voltage would go up to about .7. That's on a 0-1volt scale 0 being lean and 1 being rich, so the numbers I'm getting seem appropriate.

thanks

<small>[ November 04, 2003, 03:23 PM: Message edited by: mxer4eva ]</small>

[JasonH]

Just an update for anybody with a similar problem: I haven't had any error codes and the engine has run fine ever since I changed the fuel filter. I have to assume that it was the culprit, at least this time.

[esoterikest]

how good are these compared to 11027 sensors?
http://www.nopionline.com/nopistore/dsp_part_detail.cfm?vmakeid=220&vmodelid=108&vcatyear=1992&vnopinum=973%2B0267&vTitle=MAZDA%20MX-3%201992