My '03 RSX base had the 'check engine' light come on Saturday. I had it
checked at AutoZone, and the code was "P1078". They said it was a
proprietary code with Acura and I'd have to go to a dealer to have it
checked out. I called the dealer and they wouldn't tell me anything over
the phone, but said it was ok to continue to drive it unless 'driveability
suffered'. I reset the light, and have put over 100 miles on it without the
light coming on again. I did some research and found that the code means
"P1078 Intake Mainfold Runner Control (IMRC) System Malfunction (High
rpm)"...but don't know what that really means in English. Anyone help?????
In plain English, your engine has a special door inside each manifold
runner (there are four) that restricts the amount of air entering the
cylinder. Above 5,000 RPM, these doors open, admitting more air. Your
engine computer has decided that something has gone wrong with the IMRC
system, and has illuminated the MIL.
That the error code starts with "P1" rather than "P0" means the code is a
voluntary code that Honda put there without a diktat from the EPA. Honda
included it as a diagnostics tool.
A P1078 error can be set by a number of things that control the IMRC
system, anything from an IMRC valve that won't hold vacuum to a failed
electrical component. And if the history of such things holds here, it's
entirely possible you're seeing the error on account of something that has
nothing at all to do with the IMRC system. This is why the dealer won't
tell you anything. They have to snoop around and do some tests before
deciding on a culprit.
The correct procedure in such cases is to reset the MIL, then just drive
the car as normal. If the light comes on again with the same error, then
they get serious about it. A large number of errors are transient and do
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