First, I really appreciate your discussion on the effectiveness of forums. As a member of several forums I am reminded of the techniques which make them work best. As a pre-teen I remember asking my mother what the washer was doing, not what she thought was wrong. As a service technician for SIMPLEX I learned the meaning and value of “Closed-Loop-Service,” dependent on accurate descriptions of symptoms! So, here is information, maybe more than what you wanted...

‘92 DeVille, 4.9l, 206,303 miles

We bought this car in November of 2014 and drove it 150 miles to home. It ran rough when we bought it but I figured it was engine tune-up so I took a risk. We like Cadillacs (We have a ‘94 DeVille, this ‘92, and an ‘89 DeVille) but my background and experience stop at carbureted engines (My “baby” is a ‘81 ElDorado - the diesel having been removed and replaced with an Olds 350 by a previous owner) and my son has a ‘78 Fleetwood he purchased for an investment.

Rough means two things, it shakes and sputters during idle (it seems to want to surge during idle in Drive) and from cruising to accelerate sputters and seems to lack power.

What have we done?

1. Immediately upon parking at home: Read the codes...
E13 Open oxygen circuit 27 NOV 14 N
E24 Speed circuit sensor problem 27 NOV 14 N
E30 Idle control circuit problem 27 NOV 14 N
E32 Open MAP (Manifold Absolute Pressure) sensor circuit 27 NOV 14 N
E44 Lean exhaust signal 27 NOV 14 N
E45 Rich exhaust signal 27 NOV 14 N
E52 ECM (Engine Control Module) memory reset 27 NOV 14 N
E70 Intermitant TPS Signal 27 NOV 14 N
E71 Intermitant MAP sensor 27 NOV 14 N
E91 PRNDL Switch problem 27 NOV 14 N
E92 High RPM P/N to D/R in ISC range 27 NOV 14 N

Changed oil (& filter), air filter, and checked spark plugs. The back four were very dirty and two cylinders had not been firing for some time. We then changed all eight spark Plugs.

Slight improvement.

2. Filled the gas tank with premium gas (92 octane) and ran the car a few days, no improvement. Read the codes:
E30 Idle control circuit problem 05 DEC 14 Y
E71 Intermitant MAP sensor 05 DEC 14 Y
E91 PRNDL Switch problem 05 DEC 14 Y


3. Found a broken vacuum hose (1/8" OD) and replaced. Read codes:
Codes read without reset or running engine 24 DEC 14
E30 Idle control circuit problem 24 DEC 14
E32 Open MAP (Manifold Absolute Pressure) sensor circuit 24 DEC 14
E71 Intermitant MAP sensor 24 DEC 14
E91 PRNDL Switch problem 24 DEC 14


4.Test Drove and read codes:
After test drive
E71 Intermitant MAP sensor 24 DEC 14


5. Replaced MAP sensor. No serious improvement.

We have since driven the car very little, although one short trip (2 miles) at 25 MPH the
car ran very well while cruising, same issues with idle and acceleration.

We have the full service manual from Cadillac and it is time to get serious. I found post that discussed a potential vacuum leak, which in the absence of error codes on injectors might be a possibility (?) And would be less expensive than eight new injectors. I am leaning towards new injectors but chasing a vacuum leak will be less expensive. What say you?