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Looking for a little bit of mechanical advice. A couple of months ago, the oil filler tube snapped off in my hand on my 997.1 C2S, as is pretty common. I decided to get my hands greasy and replace it myself. After about a week of driving, the check engine light came on. The code is P2188: System Too Rich at Idle Bank 1. I thought maybe the computer needed some time to relearn, so I cleared it out, but it comes back on the next week.
For replacing the oil filler tube, I disconnected the vacuum line and MAF from air box, took the air box out, belt off, idle pulley off, alternator out, and oil filler tube out. Of course, did the reverse to put it back together with the new oil filler tube.
What I've tried so far to remedy the issue
Checked vacuum line to the air box. I checked as much as I could of the other vacuum lines. All seem to be connected, but perhaps I missed one deeper behind the engine (not entirely sure where they all run to)
Spray cleaned MAF and throttle using appropriate cleaners
Poor man's smoke test (big pull on a cigar and blow into one of the vacuum lines) No visible leaks
Ensured it's not "bad gas" or a loose gas cap
Replaced the oil filler tube a second time to make sure it didn't have a crack or leak in it
Took the oil cap off while running, and it definitely makes the car rough idle
Disconnected the vacuum line from the air box, both when the car is running and after it's off, to verify it had vacuum pressure
Shook my fists at the heavens
No luck on any of that. I'm out of guesses, so any wise words you might have, please feel free to share! Otherwise, it's off to the dealership to let them do a thorough test.
You probably have a secondary air leak from the filler neck itself, possibly the o ring into the engine case, or another vacuum line you didn't actually touch was disconnected due to a lack of flexibility with age/hardness when bumped or pulled while working.
A MAF sensor concern would typically cause both banks to run lean, at which point the DME would begin adding fuel to compensate before reaching a maximum value, ie running rich. If only one bank is affected, then it is more than likely on the intake side. And typically, the last thing touched will be the cause of your new issue.
A real smoke test may be needed.
You are correct. And it more than likely is running lean, but the DME is actually correcting for it to the point that it sees a rich condition on the back end. It's smart enough to correct for a deviation in optimal fuel trim, but not smart enough to know why. And it really depends on what the actual break down of the fault is after P2188, lower rpm range or at idle, and more importantly, what the actual fuel trim is, negative (taking away) or positive (adding).
The only mechanical causes for a true rich condition, which are rare, would be the MAF misreading, which again would typically cause both banks to run rich, a leaking injector on that single bank, excessive fuel pressure (again hard for just one bank due to a shared system), or the tank vent valve not closing, ie allowing for additional fuel vapor from the tank (which again vents into the shared intake).
Here are just two of the four factory break downs for both a lean and rich condition, both under the P2188 fault for reference. Hence why I love when people assume a computer tells us how to actually fix the car!
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Smoke test was fine. Got a new MAF in today. Will follow up if the code comes back on (both P2190 and P2188 codes are present now. Effectively same issue, but now both banks)
07-14-2018, 01:24 PM
Error code P2188 - appreciate any help!
