I do not have any data streams but smoke test was going to be my next task. PCV valve and grommet are two smart things to replace, especially since they are so inexpensive. I just ordered some from RockAuto and will be delivered on Saturday. What method do you use to collect data streams? I just have a simple OBDII reader that I use for troubleshooting codes.

 

The torque pro app can do that.

 

I use car scanner pro with a generic BT ELM327 (Veepeak I think?)

Main thing you're looking for is if the long term fuel trims are high, while short term fuel trims are close to zero. If that's the case, then you 100% have a vacuum leak somewhere.

If you rev it, and then the long term fuel trims DROP, but not quite to zero, that's also indicative of normal behavior in general, so that means almost everything else should be working.

 

Thank you for this.
I just ordered an AD410 that does live data stream and smog readiness for $38. I'll check the data streams, replace the PCV and grommet of it looks bad, and check the data streams again. If it's still bad, it will be time for the smoke test. I'll update with the results this weekend.

 

Is a long fuel trim of 15% considered high?
​​short term at -1%

 

Yes, high. You have a vacuum leak somewhere.

Long fuel trim should be 0% in a system with no leaks assuming short term fuel trim is also at 0%.

Long term + short term fuel trim, with no vacuum leaks, should summate to 0.

PCV system is my first suspect, followed by intake manifold. Smoke test obviously would be good if you know someone with it.

 

I already replaced the PCV and grommet. No change. Smoke test is next.

 

No vacuum leaks found.
I inquired with my local mechanic and all he can think about is a fuel pump or fuel pressure regulator that sometimes is having issues, but not all the time or big enough to be a constant problem.

 

What doesn't make sense to me is that short term fuel trims are staying at zero, or around zero. That would imply that your fuel pump is consistently bad and running lean in such a way that it causes long term fuel trims to compensate... which could be possible, but also seems very unlikely to me.
Do you have a graphed version of the long term and short term fuel trims? Maybe these are one off spikey occurrences instead of consistent occurrences.

I'd also take a graph of the oxygen sensor voltages as well to ensure those are working as expected (revving you should see the graph spike, then settle back down to the lower value).

Should also check the MAF sensor graph as well to ensure stuff is working properly.

I wouldn't throw a new fuel pump/fuel pressure regulator at the problem since you said you replaced those already.

 

Unfortunately, I am back in Singapore for several months of work so the S2000 cannot get any more troubleshooting for now. When I get back, I will get more data and graphs of fuel trims and oxygen sensors. The Oxygen sensors were brand new Denso. From what I recall from watching the graphs were that they were consistent. I did not look at the MAF sensor. I have not replaced the fuel pump and fuel pressure regulator. I just tested them per the Honda manual and they checked out to be fine.