Two odd lean conditions

[q2418130103p]

Oh yeah, you guys are totally right, I'm not sure what I was thinking.

Anyway, I replaced the diaphragm in the AFPR as a precaution. That didn't change anything. I didn't check the ISC, nor the fuel pump relay, yet. I did a pressure test as well. I tested both with and without the TB blocked off, both tests seemed fine.

I got a couple more logs, one of which shows the behavior where getting into boost gets me out of the lean condition. At first glance it looks like it might be getting under control right at the point where the car goes open-loop (based on load, rpms and tps). Without having really looked at the log yet this sounds like the short-term fuel trim may have gotten really off. Anyway, I'm going to check a couple other things today and try to analyze those logs before I post them later.

[q2418130103p]

Welp, I made a few changes and I wasn't able to reproduce any of the 3 issues in 100 miles of driving. I'm not saying its fixed, cause that seems to be the thing that breaks it.
Here's what I did this weekend:
- Lowered 'Fuel Pump Relay Trigger Load' so that the fuel pump is always 'high' (mind you... my fuel pump is hot-wired so this signal is really just feeding the relay in the trunk so who knows if that did anything)
- Lowered the throttle position sensor by ~1%. The TPS was adjusted originally according the the manual (using the appropriate feeler gauge), but I noticed that after driving for awhile the TPS would creep up to almost 14% at idle. I decided to drop it to 12%. I don't really think this mattered at all.
- Tightened the BOV. I didn't think it was loose before, but I guess there was some room for adjustment still.

I probably wont get to drive it again until the weekend. Hopefully its either still fine, or I get another log or two.

[Greg E]

Open atmosphere BOV?

[q2418130103p]

Yea. I'm actually working on changing it to recirc, hasn't happened yet though.

EDIT - BTW, this is hardly scientific but I loosened the BOV 1/8 turn (so still 2/8 turns tighter than before) and notice that I was getting a couple of the issues again. Not nearly as bad as before, and not repeatable like it was before. The two issue were the 'lean idle after engine braking' and 'random lean cruise until getting into boost'. I haven't noticed the 'occasional lean spike during light acceleration'.

[q2418130103p]

I've had this car since 2005, and when I got it there was already a chinese knock-off open atmosphere BOV in it. Ten years ago I bought a nicer BOV, and an adapter to recirc it. I put the BOV in but was too lazy to install the recirc fitting. So it sat on a shelf for ten years. That is the single biggest mistake I have ever made with this car, and that's really saying something... I switched to recirc this weekend and now I have a completely different car. It's so much easier to drive, the RPMs stay between shifts much better than I could have expected, its so much easier to shift.

I drove it over 100 miles like this. I slightly experienced issue '2' once (lean spikes during very light acceleration), but neither of the other two issues. And honestly, the one I did experience is not a big deal in the slightest although I do think it is still abnormal.

To summarize:
- Switched BOV to recirc, very pleased with the increased drivability (maybe thats the wrong word).
- The issues (at least 1 and 3) seem to be totally gone
- Issue 2 persists, but very rare, and very slight. I will still pursue this and try and get another log.

[Alex3000gt]

Case closed, then? Glad this had a good ending.

[q2418130103p]

Yeah, I think so.

Well this at least marks the "end of major combat operations", but I'll probably keep thinking about the remaining issue (the lean spikes during very light acceleration). But at this point its really being nit-picky.