WUE, boost and misfire

[Dan_Austin]

While my engine is warming up I try to stay out of boost, but occasionally it does
happen. I have been chasing what feels like a sever lean misfire, but it only occurs
during warm up, and the events I have captured in a log show that I don't appear
to be going lean.

My thought is a combo of a rich warm up state with accel enrichment and perhaps
'cold accel multiplier' (If I understand its purpose correctly). I'd appreciate any
feedback on the tune and the log, even if the advice is 'Don't run the engine under
boost until warmed up'

The attachment CurrentTune.msq is no longer available

CurrentTune.msq

(30.32 KiB) Downloaded 208 times

[dontz125]

"Don't run the engine under boost until it's warmed up."

Seriously, that kind of sudden heat and power load can do bad things to your engine. The two-smokers in the audience have probably heard the term "cold seize" - the GP racers most certainly have, and probably the MX riders as well. If you put too much heat into an engine that isn't uniformly up to temperature, the piston can expand suddenly and more quickly than the cylinder (surrounded by still-cold water) can accommodate. Squeak!

The first thing I noticed, looking through your msq, is that you've selected a Sequencer. Really?

Your VE map looks odd; your value at 200kPa isn't even remotely 2x the value at 100kPa. My knowledge is focused on the Extra code; one of the main things to look for in a situation like this is whether the tuner has "Multiply MAP" turned on. I don't see an option for that in this msq; could one of the B&G tuning experts chime in on this?

[Dan_Austin]

It is indeed a sequencer, and the I don't think the B&G code has
an option like 'Multiply Map'. I've auto-tuned up through 150KPA,
and have the MBC set to that point. I will review the regions
above 150KPA before I consider adjusting the MBC.

I am also into old school 2 strokes, and familiar with the cold
seize situation. This event really only occurs in one spot on my
commute, a semi-blind freeway on ramp close to home that
does not have much of a merge lane.

[Dan_Austin]

I think I may have solved this, and while WUE not the cause, it did help expose it.

After having the car painted I started having mid cruise misfires and idle stalls.
I suspected bondo dust had infiltrated the TPS and took a log to try to catch it,
and catch it I did. I has having random and complete TPS signal drop-outs. Not
noise or minor swings, but signals dropping below zero on a calibrated TPS.

I started by checking to see if the 240SX TPS had known issues, while not completely
trouble free, nothing stood out. I start with research as this was a new TPS. I was
all set to review my harness, but decided to start with the one connector pair that
I did not pin and assemble myself, the TPS itself. Upon moving the connector to
examine it and to prepare to disconnect it to check for corrosion, the TPS signal
pin literally fell out of the socket. Putting the connector down and the pin slipped
back into the connector.

I found the pin lock not fully pushed out, and the connector socket worn where the
lock pin should catch, so assembly took a couple tries to get a solid connection. With
that minimal fix the issues I was chasing went away, and as an extra bonus the
boost misfire during warm up also went away.

The loose pin would cause a drop out causing fuel cut, then a huge AE spike when the
pin reseated, add in the WUE and AE cold multiplier and I would get a huge shot of
unneeded extra fuel. One lousy pin in a factory assembled connector and the car
runs better than ever...