2003 Buick Century w/3.1; Timing Adjust Project

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#1
Hi guys,

How is the ignition timing adjusted on a 2003 Buick Century with a 3. 1 liter engine? The reason I'm asking is that I've got a theory that I want to prove out on this particular car. I had a 1990 C1500 with a 5. 7/5 speed combo. I was able to bump the timing a maximum of 3 degrees while always burning reputable brand, premium fuel. There was no problem with pre-ignition and I saw an increase in fuel economy. Around the same time I also switched everything over to synthetics. The net result after everything was an increase in economy from about 13 mpg to 17. 5 mpg along an increase in seat-of-pants performance. This was stuff that I have done on all my 60's muscle car restorations.
I know there is a way to adjust timing on a modern engine, just don't know how to go about it. What equipment is needed? For approximately 80 cents more per tank fill-up of premium, I'd be willing to run better fuel, possibly get more mileage and maybe a little more power. I figure the engine is tuned for any old 87 octane fuel available at any corner station. The hot rodder in me says there has got to be more to it if I at the very least commit to burning a better fuel.
Help me out guys.

Thanks,

Nick
 

Gus

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#2
I would say no...you are trying to make a Century into a muscle car?

How much savings are you going to get, by paying for premium instead of 87 octane?

There is no adjustment since this is a DIS system.......fuel curves are built into the PCM using 87 octane......there may be some companies out there who can change this by programming your computer, sorta like the "old days" when you could put a preformance chip in the ECM....of course, then when you have driveability problems, this creates a new set of problems when scan tools don't recognize the vehicle....
 
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#3
The savings might be minimal depending on the cost of fuel. The hotrodder in me says there must be a little more in it than how it is after the factory pushed it out! When my grandma's car is making the same amount of power that mine is, something needs to be done. Haha.
That '90 C1500 could keep up to a chipped '92 K1500. Granted it wasn't an apples to apples comparison but there was a performance gain.
If i picked up another 2ish mpg, it's like a free gallon of gas. The cost of the premium vs regular just about breaks even when it's 2 bucks a gallon. At 4 bucks I'm saving money. No matter what I still get that performance kick everytime the accelerator is pushed down.
 
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#4
Hi Gus,

I worked a part-time job as a mechanic back in the early to mid 90's while in college. Our chief mechanic at the time had some sort of small black box that I remember him plugging into one particular car to adjust the base timing. I don't remember what kind of car it was or anything else specific. My memory only remembers that it wasn't a widely used tool and it was something he didn't particularly want to buy at the time because of cost and the amount it was going to be used. (the payback was pretty poor probably. ) I remember him having a small window of adjustability on that particular vehicle. I wish I had paid more attention at that time.
Is my particular car only capable of maintaining a specific base timing and it can never be adjusted?

Thanks for your help,

Nick
 

Gus

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#5
Base timing is non adjustable......timing is adjusted by the computer, based on info from the different sensors in the vehicle.....

In pre-OBD II vehicles, computers used "chips" which contained all the programming for the computer.....'"performance" chips were available then, just remove the old one and install the new one...voila!

Today's cars are programmmed via the internet......don't know of any companies out there that provide "performance" programming for street vehicles.....plus the special equiptment that would be needed to communicate between the pc and the vehicle......
 
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#6
Thanks for the feedback Gus. I'll just have to figure out a way to be satisfied with the same level of performance my grandma has in her vehicle I guess. Haha.
 

montego_gto

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#7
Re: 2003 Buick Century w/3.1; OBD P0404 Code

Guys,

My Buick check engine light came on yesterday. I check the code and the only one logged was P0404. The vehicle has 149000 miles on it. I don't want to just hang a EGR valve on it without verifying that is the problem. How else should I test it to verify there is a problem?

Thanks guys!

Nick
 
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#8
A good engine capable scanner and some good repair info is required to test it out.
http://www.alldata.com/products/diy/index.html

Also run your vin for tsb on it.
There may be a VCM/computer reflash to cure that problem.
Crunch
 

Gus

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#9
Crunch is right...

You need a scan tool for diagnosis.....this code is set because the PCM commands the EGR to open to a certain percentage...there is a feed back circuit in the EGR, which gives the actual pintle position....

So if the PCM commands the EGR to open 40%, and the actual pintle position differs from this by 15%, this code sets....
 
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#10
It seems to me that if the crank and cam sensors were re-engineered for adjustability, timing could be adjusted.