pat056

Check engine light came on after roughly 100 miles of starter replacement. I found a vacuum line that I didn't reinstall and corrected. 100 miles later, engine light came back on. Being short on time, I took it to a recommended mechanic. He just called and said I have a "lean short term fuel system failure". I asked for the code and he said several that all relate to short term fuel system failure. My question; is this possibly related to a different vacuum leak or something else I missed? Will it cause damage to drive it the 70 miles home? I'm not sure this mechanic knows what he's doing.

PorscheDoc

Usually as long as the light is not blinking, you are safe to drive it home (don't hot rod it, but rather normal easy driving)

Barn996

Do you have a code reader? If so post the code and we'll chime in. As mentioned, a flashing CEL = don't drive.

pat056

I don't have the code. Mechanic said there were several that all related to lean bank. This doesn't make sense to me. I would think there's a code or he's using a cheap code reader. Either way, that's why I'm picking up the car and not letting him fix it. He said he removed the throttle body and I asked him just to remove the t-manifold and see if there was a vacuum leak there (ie line not connected or loose) and he said that would take more time than he had allowed???? It's only loosening 4 hose clamps to move that T-manifild and look behind it.

fpb111

Sounds like vacuum leak.

Macster

Why do the lean bank related codes not make sense? You apparently forgot to attach a vacuum line which suggests there is a vacuum leak, an intake air leak.

Now what may be throwing you is the leak is a biggie at idle the air coming in represents a considerably fraction of the total amount of air the engine requires at idle and very little load. Thus the engine controller will have to go way over to the rich adaptation to compensate.

But if you got on the highway and drove the car at higher engine speeds the amount of air that makes it through the tiny vacuum line represents a much smaller bordering on insignificant fraction of the total amount of air the engine requires at this higher engine speed and load.

So, you drive a while and then arrive at your destination and while driving slowly and possibly encountering some stop/go traffic and idling the light comes on cause the engine controller finally reached the max. threshold at which it could continue to add fuel to compensate for the vacuum air leak that is the unattached hose.

Connect the hose. Clear the DTCs (diagnostic trouble codes) (even if there aren't any currently logged/present) and then see if the problem returns.

Sincerely,

Macster.

pat056

That makes me feel better. Makes sense because the idle was a little high at first, then seemed to be OK. My ride home is all interstate and so it sounds like the issue will be minmized. Now to figure out which vacuum line I didn't connect...