Wee Willie

My car has been running crappy for a long time but lately has had periods of running quite well.

I've read that its particular symptoms might be caused by a bad O2 sensor but have been having some difficulty finding exactly where the O2 sensor is located and what it looks like. I couldn't find any good pictures in the shop or parts manuals and the only picture I found on the net is of a modified engine that makes it hard to figure out how it relates to mine.

I've attached a Jpg of a sensor with 2 wires that are corroded completely off. Whatever it is isn't doing what it's supposed to. Is it the O2 sensor and if not, do you know what it is?

I hope the picture isn't too big to attach to a message.

Here's the link to the picture:

http://s1017.photobucket.com/albums/...urrent=O2a.jpg

Thanks for any help.



Don

lonetlan

The O2 sensor is on the exhaust manifold, almost under the car.

Wee Willie

Could you see the picture that I posted?? I edited my original message and included a link to the picture.

Thanks,

Don

puhpaper

iTrader: (6)

that is in fact not the o2 sensor. Here is a FSM illustration i pulled from atkins rotary. This illustration is for the Turbo II, but the exhaust manifolds are similar, just ignore the turbo charger.

The O2 sensor is circled in red. Everyone's got to start somewhere.

duo2999

iTrader: (1)

the pics. its part of that thing that the airpump goes to.

i take it that this is a n/a s4?

you should probably find a replacement one.

its part of the air check valve i think. i checked the fsm to see what it calls that. im sure it has something to do with air given the name. hopefully someone else can fill in what it actually does.

Wee Willie

The reason that I asked is because the picture on this web page looks like it's pretty close/near to what I showed in my picture.

http://robrobinette.com/o2_sensor.htm

I wonder what my broken sensor is?? Whatever it is it's pretty obvious that it's toast. But from my symptoms, I think my O2 sensor probably is also not working correctly.

Thanks,

Don

RotaryRocket88

iTrader: (7)

That is the split air solenoid on the ACV. It is strictly for emissions purposes in 5th gear.

puhpaper

iTrader: (6)

yeah, your part that you pictured is on the intake manifold, the O2 sensor is literally on the exhaust, but the very top of it, near the exhaust manifold.

puhpaper

iTrader: (6)

I did us all a favor, and just searched for it on ebay. Fortunately someone had one for sale. Here it is pictured.

RotaryEvolution

iTrader: (30)

cause common sense is so hard to come by these days.

unfortunately that is for an S5 and will probably confuse the OP further. the plug is either yellow or green in color on an S4 and is square in shape. the OP's car is an S4 non turbo as you can tell by the pic.

puhpaper

iTrader: (6)

fail on my end

bostonspgs

iTrader: (1)

o2 sensors say she is running rich or lean by the temps in the manifold , if its fried the ecu has a set program to avoid reading it and puts it on a premeasured cycle, this shouldnt affect its running condition all that much , fuel economy however goes down the drain cause the egr can be skipped

Wee Willie

I've read a couple web sites that say bad O2 sensors can cause bucking and all kinds of strange problems that can be difficult to figure out.

My car is a 1988 SE, n/a. One of its symptoms is bucking. It mostly happens when transitioning from closed throttle to mild/moderate acceleration in traffic. Also, almost always when shifting from 1st to 2nd gear their is a "buck". I don't want to use the word "miss" because it clearly isn't a problem with plugs, plug wires, etc.

A couple months ago I noticed that if I rev it up to about 3K when I start it, and hold it their for about a minute, the car often runs significantly better. It runs smoother, is less likely to "buck" on the 1st/2nd shift and probably makes about 10% more power. That doesn't always work but it seems to work about 50% to 70% of the time. That's often enough that there is very likely a cause/effect.

The car has about 185,000 miles on it so I thought it had just been suffering from low compression and the effects of old age. But a couple months ago it started having these periods of running great. Now I'm baffled and would like to figure out the problem so I can fix it and have it run great all the time.

Thanks, I need all the help I can get.

Don

RotaryRocket88

iTrader: (7)

The 02 sensor is not used under any kind of acceleration. The ECU only pays attention to it while you're cruising at a constant speed. Your problem sounds more like it's injector or grounding related. Do you have any trouble hot starting the car? Or the dreaded 3800 RPM hesitation?

Wee Willie

Yes, the 3,800 RPM hesitation is actually worse when it's in one of its "running better" periods.

I have had intermittent "flood start"problems for a dozen years. I guess it started happening at about 120,000 miles. Some times it was on cold start but also happened after running the car then allowing it to cool for a couple hours. For about 2-3 weeks I've had several times when it wouldn't start when it was dead cold but also after it was hot and then sat for 30 minutes or so.

Do you think it's leaky injectors and a grounding problem? Any good way to test injector leakage without removing them?

I had given up on it thinking that it was just worn out but since it's been having these periods of running great I'm hoping that I can get some more miles out of it without having to do a complete engine rebuild. When it starts running well it's amazing.

Thanks, I do need the help.

Don

RotaryRocket88

iTrader: (7)

Any sort of flooding will come down to dirty injectors or low compression. You can do a compression test to rule that out, and allow yourself breath a little easier. The FSM also has an injector leak testing procedure that you can follow. The secondaries will be somewhat easy to test, but the primaries will require the manifold to come off. The primaries are going to be the prime suspect though, since they are used more often, and are the only ones firing on startup. A full servicing by a place like Witchhunter.com will take care of anything you can't visibly see, and they'll also replace pintle caps, o-rings and grommets. $19 an injector isn't bad, and they're even in the same state as you (WA).

As for the 3800 RPM hesitation, there's no consensus on it, but some have had success by splicing into all of the ECU grounds and connecting to a second, good ground location near the ECU itself. You can also clean up all of the existing grounds for added insurance: http://www.aaroncake.net/rx-7/grounding.htm.