Wont stay running
 

Hey everyone

New owner and member. I bought a well cared for one owner 2002 Boxster S with 42k miles earlier this year. Love the car and have put ~4k fun loving miles on with no concerns, until this morning. Yesterday I drove the car to work and back (~35 miles) and took my son to dinner (~5 miles). I let him drive the car home (~5 miles), he's never driven a stick but rides bikes and understands a clutch. He did the normal stall, buck, and miss shift a new driver does and got us home.

Car would not start this morning, so I took another car and decided to look into the issue tonight. Car does start now, idles high- about 1000 rpm, and sputters and dies when I goose the gas.

What gives? Son's lesson seems coincidential but...

No Check Engine Light? It could be a few things, fuel filter, MAF sensor, or vacuum leak somewhere? I would search for a vacuum leak first, maybe a vacuum line/link got jolted lose?

No CEL. Pulled the engine cover and will look for leaks. Just read a post about over filling gas and soaking the evap canister... any experience with that? I'm going to change sparks and air filter while I'm in there too.

I have never had an issue when over-filling the gas tank... I can't imagine that being a problem. Anyone out there heard of this?

sparks are underneath :)

sounds like a vacuum leak. gas cap and oil cap on tight?

Everyone seems on the right track - seems to be fuel/air related. Another component to consider would be the fuel pump.

I've had this problem on my previous Boxster. It was not the MAF in my case, I personally wouldn't start there. My car had a vacuum leak at the time but even after fixing it the car kept dying right after startup.

So.. what was the problem?
How did you fix it?

I've filled my tank so high that gas ran out on the ground and didn't get a CEL.

Simple fix, I rear ended someone when I was sick and not paying attention to the road. It racked up about 12000 dollars in repairs so it was bought out by the insurance. In other words, I have no idea what actually caused it.

Update

Didn't find any vac leaks, replaced the sparks and air filter while I was there- wasnt sure the last time they were replaced, all looked fine. Didnt fix the problem.

Unplugged the MAF sensor and idle smoothed out, stayed running and did not miss when given gas. Problem solved, right?

No. replaced the MAF sensor and still the same issue. Starts evey now and again, idles rough when she does, pops and stalls if given gas. Unplug the new sensor and she starts right up, idles fine, and revs when given gas.

What next?

Played with it some more and problem is there with and without the MAF sensor plugged in, seems better with sensor unplugged- starts more often, idles smoother, revs if gentle with gas. Still no CEL or codes. Maybe I should roll it over a cliff.

Did you disconnect the battery? I think the computer needs to relearn the fuel trims with a new MAF. Reseting a CEL also forces a relearn I found out. Also there is a e-throttle learn/calibration that you perform after reconnecting the battery by turning the key on and waiting 60 seconds, then removing the key. It's doubtful these are going to help you very much but you should probably try them anyway.

A new MAF fixed my problems. You could buy a Durametric and examine the fuel adaptation readings and the MAF readings. My MAF readings looked good and fuel trims were out of wack but a new MAF brought the fuel trims back to nearly perfect.

Given your scenario re. son stalling the car with the clutch, I would take it to a dealer to insure that the sudden stall didn't cause the timing chain on one or more banks to jump a tooth. 42k isn't necessarily low miles so far as timing chain tensioners are concerned.

This is not likely to be the case, a remote possiblility. But if it somehow did, trying to start and rev it isn't going to do it any good, but could cause further harm.

Especially since you've already swapped plugs and MAF plus searched for vac leaks and still no-joy.

Your car, your money, your decision. But, after all you've done, this would be my next step.

Cheers!

Problem solve
 

Fuel pump fixed the issue. Its been a week since change and car runs like a champ again. Mechanic explained that the AZ summer heat kills plastic pumps, running low on fuel exposes the pump in the tank and allows it to heat up and degrade.

Thanks for all the help- I hope this helps someone down the road too

I love simple solutions. That's why I don't try to diagnose and fiddle with issues that will take me weeks and a qualified mechanic hours to fix. Congrats. on the easy repair.