Cold start issue: 2.7L Stumbling/Stalling UPDATE: Fixed

That is super helpful! thank you a ton....seems that those trims for bank 1 are more or less okay

 

Technically they're not at the point to set a CEL, but as soon as your O2 sensor comes online it's dialing back the trims -10.4% which is considerable and at the end of the log its still requesting a -7% reduction in fuel. The LTFT is okay though so it isn't a huge concern, just an oddity

 

Wouldn't a cracked head also lead to coolant in the oil...which should be pretty easy to see by pulling the disptick?

 

No sir, well not unless is was a massive crack, in which case you'd probably hydrolock before it had chance to seem by the rings and contaminate the oil

 

Right, but it's adjusting to make it more rich not lean, or do I have that backwards I can never remember. Which is kind of the opposite of what we were thinking with a lean cold start. So could be a rich cold start and can't get enough air? VSV letting vapors into the intake when it's not supposed to? Many things to consider...what should be my next steps going forward?

 

It's got a very rich cold start by that log, as soon as the O2 comes on line its asking the computer for a huge reduction in fuel

 

I should mention, that cold starts are often rich anyway, same concept as choking a carburetor, need more fuel and less air when cold starting. Maybe make a warm start log if it has the same symptoms to rule out cold start enrichment issues

 

Yeah I know rich on startup is normal until o2 sensors start working, but how rich is too rich is the tricky part. I'll get a warm start log later...I'm a biggg data guy and I don't like throwing parts at things so I appreciate the help. I'm still reading that coolant temp sensor could be the issue, I might take a look in my FSM and see how to test it.

 

well, usually it only is a problem if it is reading wrong, in your log it shows around 79*, if that was the ambient then it is working

 

Damn, that's a cool little app!

Short term trims are a little funky; they're showing a rich condition, and varying a bit, but the long-term trim is showing an overall lean condition...

 

Hardly lean for an engine with 160k miles though. Don’t think valves have ever been touched

 

Eh more or less, it was about 68-70 F that day

 

I don't blame ya, I'm into it myself. I just used one of my logs for my BMW to diagnose leaking direct injectors.

https://datazap.me/u/speedytech7/1-...ata=2-3-4-5-8-9-11-15-23-24-25-26-27-28-29-30

 

overall is actually rich, that's why it is removing fuel with a negative trim

 

Okay so coolant level is pretty low. I checked it cold. But I also haven’t checked the level in a very long time. Longer than I care to admit :/

 

Ehhh??? Wha'ch'ou' talkin' 'bout, Willis??? Long-term trim (which I refer to as "overall" since it's a calculation based on multiple engine start/run cycles, vice short-term trim which is just "now") is positive, which means it's compensating for a lean condition; the short-term is negative, meaning a rich condition, hence my use of "funky". If LT trim is positive, I would normally expect ST to be either neutral or positive, but NOT negative.

 

My B you're right, I read the LT as negative too.

 

No worries - that data table was HARD to read, the graph, on the other hand, is very useful, and you can see how the ST drops suddenly; granted were only looking at a VERY short snippit of time, but still, it does make me go, 'Hmmm...'.

 

I love DataZap, pretty powerful little site for a total freebie. I honestly don't think I could own my stupid old Bimmer without it sometimes. The ST drops suddenly because I think the O2 heater finally brought the sensor up to temp to get a reading and the computer started into closed loop. But it is weird it isn't trimming very fast.

 

Okay I got a hot start and about 10 minute drive. See attached. I don't have to time to throw it into datazap rn cause I'm at work, but if either of you are bored feel free. No issues starting today. It really only seems to do it if its very hot and sunny out, almost like a vapor lock on a small carbureted engine.