MacCox

Ok I have a 1998 civic LX manual transmission that was having random stalling issues and now will not remain running. I have read through a lot of posts and this seems similar to many other posts but I have not been able to pin point the source of my problem.
So the issue was that the car would randomly stall but would start back almost immediately with my son while driving it. I began troubleshooting it using a ELM327 scan tool even though the CEL was not on to see if there was something obvious. No luck. What I have found is that the Main relay seems good as there is no loss of voltage to scan tool connector and I hear fuel pump run and relay kick off. Tried priming 4 times then starting, No change it will now run for a few seconds and then die. I can smell gasoline after several attempts of this. When it will remain running for over a few seconds it will idle but if you press the throttle the car will stall. I am currently leaning toward this issue being a IAC valve problem but I am not confident.
I have attached the data that I gathered from the logger tool if this will provide anyone with an Ahh Ha moment thus far it has not for me.
****Update****
I have replaced the fuel filter and it was extremely dirty. I have also removed and cleaned the IAC which had some carbon/dirt inside but the problem persists.
Any suggestions would be appreciated.

ezone

Looked at data........ trip 3 chart 2 seems to show an issue where the yellow line hits bottom and the blue line spikes high...... which (I'm having a hard time reading your graphs) hovering my cursor seems to indicate fuel trims are reacting correctly to O2 sensor values.....which makes me look at the raw data......

Problem is, in staring at the raw data I see fuel trims reach extremes in both directions at random times.

UNPLUG the front (primary) O2 sensor and then go out and drive it a while......long enough to figure out if the problem no longer occurs.

ezone

I shoulda asked, is the CEL on? Has it set codes related to rich or lean fuel trims, or any O2 sensor related codes?


In the reply above, add: After unplugging the front O2 sensor, disconnect the battery for 10-15 minutes --- not only to erase odes, but to clear out learned fuel trim adaptive values

MacCox

ezone, Thanks for the reply. I will try unplugging the O2 sensor this evening. There are no codes at all. I did get a code after cleaning the IAC but it was because I had left one of the sensors unplugged when putting the air intake back together. I plugged that back in, cleared the code and the CEL went back off. To be clear the front O2 sensor is the one that is on the exhaust manifold at the front top correct.

Colin42

yep that one

MacCox

So I did unplug the front O2 sensor and left the battery disconnected for around 15 minutes. Went out driving around and the car stalled once not long after I was out driving (less than 2 minutes after starting) but after that there were no other issues. With the front O2 sensor disconnected the CEL was on as expected. My gut feeling is that this is the issue but I am still unsure why I got the one stall. If it had not stalled I would have said that is the issue for sure. Iam going to drive it around some this weekend if I have time and see if it stalls anymore. If not I will be ordering a new O2 sensor.
Thanks!

ezone

Can you connect your scanner and get another data recording if it stalls again?

Could easily be more than a single issue.

MacCox

The scanner has remained plugged in but no additional stalls have occurred. I have ordered the O2 sensor and I will do another data logging after I have installed the new sensor to compare the new vs the old.
Thanks again.