We Need You!

Caddyinfo Discussion Forum

Support Caddyinfo.com There are two easy ways to contribute to Caddyinfo.com
1) Caddyinfo Discussion Forum Contribution or Subcription click here
2) Direct contribution via Paypal, click the button below.

Join the forum
Join the Caddyinfo.com forum and share your knowledge of Cadillacs and Cadillac Culture.

Write Cadillac Articles Email or post your articles to share with other Cadillac enthusiasts!

Caddyinfo's Cadillac How-To Section

Cadillac Rough Idle

2000 Rough Idle FAQ

 re: Mikes Rough Idle concerns  bill  0:15 am wednesday march 27, 2002
The issue of idle quality involves the engine and the vehicle it is mounted in.  There are three basic platforms the "new" Northstar (2000 or later).... the Eldorado, the Seville and the Deville.   If you put the same engine in each of the cars it would appear or feel to idle the best in the Eldorado, second  best in the Seville and worst in the Deville.  The 2000 Deville platform uses a different style engine mounting scheme that provides much better isolation at road speeds and less torque steer but , unfortunately (you know the deal about no free lunch..), has poorer idle isolation.  The field complaints of
rough idle surfaced on the Deville once it started production in 2000 model year and prompted the cam timing changes.

The Northstar went to roller cams in 2000.  The actual valve events are basically the same from 1993/99 with the direct acting tappets and in 2000/early 2001.  Idle quality is measured several ways with the combustion stability and coefficient of variation
of indicated mean effective pressure (IMEP)  being the most common and reliable.  The combustion stability and CoV of IMEP for the 93/99 engines and the 2000 engines are virtually identical so one would assume that the perceived idle quality are the same.  As the 2000 Deville production started it was obvious that with the build variation and mount variation this was not the case.   The revised camshafts were developed to decrease overlap to improve the idle stability and perceived idle quality.  That is what the service bulletin is about.  There is nothing wrong with the earlier cams.  They perform fine but in a DeVille...some DeVilles...the slight idle perturbations are  not isolated by the mounting scheme sufficiently.  By decreasing overlap the
performance is affected very slightly....and not to the better.   That is why it wasn't done in the first place.

Why wasn't it found in testing?  Well, it was...sort of.  The engine itself was scrutinized considerably to determine and prove that the actual idle stability had not deteriorated.   The
subjective tests in the car (DeVille prototypes) showed a slight degradation but it was not felt (no pun intended) to be complaint level.  Unfortunately, in hindsight, this was not true  and the effect of build variation was not totally comprehended.  So, the
other cams were developed and released in record time.  Now they are being made available to the field as a fix for a car with chronic idle quality concerns.

This idle concern is not a major issue to me personally.  I have ridden some of the worst cars and , indeed, the engine does seem to shake more, but not to a complaint level..  It just has the feeling of a slight tremble like a higher perf cam would have.  
But, this is a luxury car, so many owners (rightly so) demand an unperceivable idle.  It is possible to provide that with the new cam profile.  I would certainly not recommend that anyone just rush out and get the new cams nor would I let it influence the
purchase of a particular car.

Neither cam is "better" as one idles a little better and the other has a few more HP.  Can't have your cake and eat it too.  I'd rather have the power.


 00/01 Rough Idle tech note  Bruce Nunnally  2:09 am friday march 22, 2002
Rough Idle
Some 2000 and early built 2001 model year Cadillac DeVille,
Eldorado, Seville with 4.6L (LD8, L37) engines or 2001
Oldsmobile Aurora with 4.0L (L47) engine, may exhibit a
condition of rough idle with no PCM DTC and no driveability

A technical bulletin is expected to be released soon explaining
that a camshaft and PCM calibration may be required. The
camshafts must be replaced on all 2000 vehicles with 4.6L (LD8
or L37) engines and the early built 2001 vehicles with 4.0L
(L47) or 4.6L (LD8 or L37) engines. 4.6L (LD8) VIN Code Y and
4.0L (L47) VIN Code C camshaft service part numbers:
12570333 RH INT
12570331 RH EXH
12570332 LH INT
12570334 LH EXH

4.6L (L37) VIN Code 9 camshaft service part numbers:
12570335 RH INT
12570337 RH EXH
12570336 LH INT
12570338 LH EXH

For a 2001 vehicle, you must verify that it has the early cam
profile by reading the 3 alpha characters of the broad-cast
code listed on the tag attached to the engine's rear cam cover.
The broadcast codes for early 2001 engines are:
Seville, DeVille applications:
Engine VIN Code Y KMA
Engine VIN Code 9 KKA
Eldorado applications:
Engine VIN Code Y KCA
Engine VIN Code 9 KBA
Aurora application:
Engine VIN Code C KY A

Once all four camshafts have been installed, the calibration
must be updated. Contact Techline and tell them that
the camshafts on the vehicle have been replaced. Techline will
provide a VCI number to install the correct calibration.
Techline must be contacted each time so that they have a record
of when a camshaft change occurred on each vehicle.
This will ensure that future calibrations for that vehicle will
be correct.

CaddyInfo Discussion Forum
Where Cadillac Fans meet to Discuss Cadillacs

Cadillac Acceleration Testing
0-60 mph, Quartermile, etc

Cadillac Performance Modifications
How do I add HP?

Ebay Auctions for Cadillac Wheels/Tires
Cardio-Doc knows Wheels

Archive of Cadillac Photos
Cars of People on the Board