: Tune-up on 1999 Deville D'Elagance



Robert Brandtjen
04-25-04, 06:47 PM
Hello everyone-

Let me first say, thanks for all the wonderful info to be found here.

I was idleing in drive at about 650-625 RPMS- it never sits longer then 2-3 seconds at 650, drops to 625 (sometimes 600) then bounces back to 650. The car itself feels very smooth but I can feel vibration in the steering wheel- not alot, but some. It will smooth out then vibrate. It is so smooth that you do not know that it is running while in Park. Should it have this vibration? I have no error codes, though about a month ago I got the EVAP solonoid code with a S.E.S. light, cleared it, it has not been back since.

OK, the car turned 75,000 recently so I decided to go ahead and put in new plugs and plug wires. I also cleaned the Throttle body and checked the EGR valve. The TB was scummy, I scrubbed it clean. The EGR was sooty so I wiped it clean and re-installed it. The number 8 plug was missing the lower platinum cap and was worn. The others looked ok but old. There has never been a missfire code or anything else- you can only feel the vibration at drive idle in the steering wheel.

At night, when it is dark and the beauty cover removed, I could see some electrical leakage from the plug wires- these are 154.00 dealer OEM wires, are they bad? they seemed to be leaking where they contacted the metal of the coil pack assembly, so I took some industrial 1/8 inch rubber and wire tied it to the back of the wires so they could not contact the coil pack.

I still feel the vibration while in drive and ideling- I never noticed this before that EVAP code- but I may be just mind screwing myself- Should it be flawless? Also, I disconected the battery terminals and waited 5 minutes for a clearing of the idle settings- it will not idle down to 450-500 RPMS as bbobynski(sp?) says it should. Idles in Park between 675-700.

I have hunted for a vacuum leak- but all of the vacuum lines are in good shape and nothing is disconected. The only other thing done, prior to the EVAP code was was that I had the dealer replace the fuel sending unit (the guage had quit functioning right. At about 35,000 miles the dealer replaced the FPR under warrenty. Let me stress again- it gets good gas mileage, is peppy as hell so......

Are the wires bad?
should the vehicle be idleing lower then 625-650?
Is that vibration I feel in the steering wheel ok, or is it a sign of something else wrong?

Thanks-in-advance,
Robert

BeelzeBob
04-25-04, 09:56 PM
First: "Also, I disconected the battery terminals and waited 5 minutes for a clearing of the idle settings- it will not idle down to 450-500 RPMS as bbobynski(sp?) says it should. " you have seriously misunderstood bbobynski....never have I said that if you disconnect the battery terminals the engine would idle down to 450-500...???? I have said that on the 93-95 Northstars and the 4.1/4.5/4.9 engines that if you RETRACT THE IDLE SPEED CONTROL MOTOR PLUNGER AND FREEZE IT the engine should idle down to 450-500.....this is the minimum air rate that the throttle body is set at for idle speed control throttle bodies. Idle speed control was last installed on a 95 Northstar. From 1996 and later the engines had IDLE AIR CONTROL....different system....idle is controlled by a solenoid that controls the bypass air around the throttle blades. In your case, you do not have idle speed contol on your 99 ...you have idle air control...so...you cannot retract the idle speed control motor because you don't have one.

It is important to understand that not all Northstar engines are the same. There are significant hardware and software/calibration changes over the different model years. Comments in a particular thread are pertinent to that specific post and the model year of the car in question....they may not apply directly to other model years.

It is normal to see some stray 'blue light" flickering around the spark plug wires in a dark place. That is called corona discharge and is more noticable in a dark place on a damp night. If you don't see/hear any direct arcing then the wires are likely fine for leakage. You can mist them with a spray bottle of water to exacerbate any leaks...look for arcs and sparks.

The occasional tremble or "miss" might be perfectly normal. It could be an injector that has an occasional drip...not good but not completely bad either. If the misfire diagnostic is not setting in the onboard diagnostics then you really don't have a serious misfire.

Personally, it sounds normal. The Northstar engine is a high performance engine that pushes the limits for cam timing and specific power. It will occasionally exhibit a slight tremble at idle or that random occasional feel of a dropped cylinder. Could be an injector that drips occasionally like I said or something else....???

I would check the plug wires for continuity and resistence with an ohm meter. Check that the terminals are in place and crimped securely on each end of the wire. Sometimes a terminal will be pulled off inadvertently or the inner core of the wire can be burned back into the sheath of the wire. Checking resistence of the wire from one metal terminal to the other metal terminal will point this out. Sounds like the plugs are good from your observations. I would check the wires and just drive it......

Robert Brandtjen
04-25-04, 10:22 PM
Thanks bbobynski,

Sorry I misunderstood your earlier post- I always thought an idle speed of around 600 was a pretty low idle speed so I was rather incredulous at 450..................

I went through that step by step tp/idle learn process and now it idles steady at 625 RPMS in drive.

May I ask? should I be looking at the struts? One of the techs at the Caddy dealer said something about charge packs ( I think that was right) and another said the computer would tell me when they needed to be worked on. 75,000 seems a long time for struts, but I'm used to 4x4's for far too long so maybe they have changed.

BeelzeBob
04-26-04, 12:51 PM
Thanks bbobynski,

Sorry I misunderstood your earlier post- I always thought an idle speed of around 600 was a pretty low idle speed so I was rather incredulous at 450..................

I went through that step by step tp/idle learn process and now it idles steady at 625 RPMS in drive.

May I ask? should I be looking at the struts? One of the techs at the Caddy dealer said something about charge packs ( I think that was right) and another said the computer would tell me when they needed to be worked on. 75,000 seems a long time for struts, but I'm used to 4x4's for far too long so maybe they have changed.

Not sure what they were talking about. Suspension is not my forte...but...I would expect the struts on your car to go 100K easily.....