: Northstar Tuneup

09-10-11, 06:43 AM
Good morning everyone... I plan on doing a tuneup to my 2002 Caddy DTS with the N*... The motor has 97,000 miles and it runs great except I've noticed a slight drop in fuel economy and the motor is at times, missing just a little bit... Very hard to notice but I have noticed/felt it... The car has a new catback exhaust and intake so I was going to go ahead and change the coolant, change the fuel filter, and check the ignition system... I noticed the coil packs are $152 per side and I was wondering if it would be a good idea to go ahead and replace those along with the plugs or not? Also, what brand of spark plugs do you guys recommend? I was going to go with either AC Delco or Denso... Thanks guys for any input... BTW, I did a quick search but didnt come up with a defenite answer.

09-10-11, 10:11 AM
AC Delco #41-987 Platinum plugs, come pregapped to .050". Nothing else. (They're made by DENSO) 13 ft/lb of torque with a tad of anti-seize on the first 3 threads.

Intake ? Did you install an aftermarket Hot Air Intake in place of the perfectly satisfactory OEM Cold Air Intake ? (Don't believe me ?? Get a ScanGauge-II [www.scangauge.com] (http://www.scangauge.com]) and monitor inlet air temperature [part of the MAF function])

Have you pulled your Diagnostic Trouble Codes from the car's built-in scanner ? A miss will usually set codes.

It's hard to diagnose the individual potted coils in the cassettes - if you have the bucks, it would not hurt to replace them, but you may be throwing away money. Talk to Chris in Rippy Cadillac parts - ^^^ Vendors.

Click on my username, get to my profile. Open the two picture albums. Ignition pictures and diagrams in those 6 pages.

09-11-11, 05:41 AM
Thanks Sub... I will check with Chris... Its a Volant Cold Air Intake... I already knew the OEM setup was well thought out, but the Volant is a sealed box and still cools the ECM like stock... I did it mainly for the sound and my intake fit almost perfect with no hangups... The Northstar sounds like a freight train at WOT with an intake... I do have an engine code, but its for the tranny saying the circut is open for the TCC and its still going into overdrive so Im not worried about it right now, I can just feel/hear just a slight miss... Glad to be talking with an ex-squid :) I have alot of ex-squids that I work with... Great bunch of guys.

09-11-11, 12:35 PM
Good to go. My STS stock-looking intake box is nowhere near stock, and it too sounds like a freight train at WOT.

Two or three years back, in here, Deville and in Seville there were a slew of threads on intake work.

EDIT: As quite a few 2000 and later Northstar FWD owners found out, intake and exhaust work without being able to re-program the PCM/drivetrain management system to take advantage of the work gets you exactly nothing but noise.

09-13-11, 03:18 AM
My next plan is getting the ECM reflashed... I heard there are some members on the forum here that know how to do and know of some performance shops that reflash ECMs... I also have an 09' Nissan Altima that I bought for my significant other... Its a 2.5 S and I put a CAI, Catback Exhaust, and a Bully Dog Programmer and I picked up 2+ mpg and a few ponies... The milage went from around 370 miles a tank to 390-400 miles a tank in city.

09-13-11, 08:46 AM
Lots of luck. Your car is no Datsun.

With a bit of homework you'll find out that there is nobody - private or aftermarket - "tuning" our 2000 - 2004 PCM's.

Read the edit in Post #4 again.

Read the third lines in Post #2 again: "Have you pulled...............".

You're in the barrel with a whole slew of FWD Northstar drivers of 2000 - 2003 cars who wish there was such a thing as a PCM tune.

09-14-11, 03:05 AM
Thanks for the reply... I will just keep hoping that they come out with something for our cars... I am interested in removing the speed limiter though... I heard a couple members here could do that for me... To answer your question about post #2, all I am getting for codes is the TCC circut open, but the car is still shifting perfect and still shifting into overdrive... Thanks for the help.

09-14-11, 10:33 AM
FWIW, In our 4T80E transmissions 3rd gear is the 1:1 gear and 4th is 0.68:1, so that's overdrive. The TCC function is not a gear or "overdrive" per se: It simply removes the last 300 or so rpm from the torque converter slip by hydraulically locking the stator and rotor together.

Take a look at the sticker on the driver's door rear edge - maybe on the rear door - depends on model. The original tire specs, build date, and speed rating are there. Your car probably has a speed limiter set to 130 mph - do you plan to take the DTS to that speed ? If not, removal accomplishes nothing. Remove the limiter and you're in the business of buying some really expensive tires - NEVER exceed a given tire's speed rating. NEVER.

Here's what the various letters in the tire size description mean.

(My Cooper CS4-V's are labeled 235/55/17 (99V) so that equates to a "149 mph" tire.)

09-16-11, 05:05 AM
Thanks for the reply... The tires I have on it now are rated for 125-130... They are H rated... I used to be tire installer at a commercial Goodyear shop and have dealt with everything from wheel barrow tires to 445/50/22.5 semi tires... I am well aware of what can happen when one exceeds the tire ratings... I was wondering about the speed limiter because I was playing around with a Fox Body Mustang and the Caddy was only 1 or 2 car lengths behind it and it cut off at 132mph... Before it cut off, there was still plenty left in it... I would estimate its good for 145+mph