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Improving an 89' Suburban 454 gas mileage


gaytrey1987
08-19-2005, 11:37 PM
Folks,

Ignore the previous postings in "Super Crapy Gas Mileage" from my username, a friend was using my computer. I need to know about improving gas mileage on my 1989 GMC Suburban SLE 454. I have followed a friends advice and gotten a new fuel pressure regulator, and pip coils...but is there anything else I can do to get this beast running well? I was the stupid one who put the wrong gas in the truck, and its been running offkey for the last 8 months.....getting 4-6MPG on the HIGHWAY! I miss driving my suburban, and I want to get it running somewhat economically so that I can drive it! If you have any tips at all please let me know!

Thanks,

William Stecker, The Tandy Collector
___________________

1929 Mercedes Benz SSK-Gazelle
1949 Chrysler Inline-8
1952 DeSoto Custom
1953 GMC Jimmy
1966 Volvo S-122
1974 Lincoln Mark IV 460 :smokin:
1977 Lincoln Town Car 460
1977 BMW 320i - SOLD
1978 Chevrolet 3+3 C/K 33 Scottsdale Prototype/Rarity
1978 Chrysler Cordoba (Rich Corintian Leather! :rofl: )
1979 Ford Grenada (Torque, the other white meat! :lol: )
1981 Chevrolet Luv
1982 Chrysler Convertable Prototype
1984 Chrysler LeBaron
1986 Pontiac Fiero SE/GT
1989 Lincoln Town Car
1989 GMC Suburban K2500 SLE 454
1990 Dodge Grand Caravan :loser:
1990 GMC Suburban C1500 SE 350
1991 Chevy Cavalier :cwm27:
1995 Geo Metro :loser:
And Even More To Come!

Ryan685
08-20-2005, 03:21 AM
This is my plan, may not be for everyone's taste but from what I've learned over the years as a mechanic working on my own vehicles, listening to customers and reading a lot. I prefer NGK EX (not IEX) spark plugs. These are the Gold Palidium wire center plugs. NGK's ceramic is better in my opinion. Choosing the right gearing for how you drive is really important. The '97 4x4 Suburban I just bought has 3:42 gears. Most have 3:73 gearing which is a bit lower the the 3:42 but for gas milage, higher is better. Driving habits I would think is more important then anything you can do mechanically. Without getting into driving lessons, lets go over as many possible fuel economy tuning tricks as I can think of.

AmzOil synthetic gear grease in the differential (s) Add a few extra psi's to the tires. Accelerate as easily as possible, back off the gas peddle to keep engine vacuum as high as possible, add a vacuum gauge and watch it, learn to drive by watching the vacuum gauge. Have the alignment checked, negative caster is desired, this allows less toe-in which means less scrubbing. Negative castor can also reduce some built-in understeer, understeer is always bad. Good shocks can reduce some of the wasted motion and keep the vehicle in a forward momentum instead of a bounce, which is wasted momentum. Big sway bars can actually cause more tire wear. I'm a thick sway bar person myself so that advice is hard to take. Check the rear brake drums, make sure the shoes aren't too tight. More often it's the opposite as the self adjusters don't work 90% of the time and you end up wearing out front brakes because the rear brakes aren't doing enough. Use a brake spoon to turn the adjusters out until the shoes are tight against the drum, then back them off until they just stup dragging. Try & keep the same number click on both sides. Stay away from oil additives, ok, maybe BG's extream bearing additive or Wynns Extend. Try & avoid short trips, hot engines burn off hydrocarbons better then cool engines. Anything you do to free up exhaust pressure can actually hurt economy. Yes it will help horsepower but at the cost of using more fuel. It's the old "more in, more out" rule (backwards in this case) Removing the fuel injectors and manually having them cleaned can really help economy. The reasoning behind it is: fuel droplets do not burn. Injectors spray a fin mist, which readily attomizes. If a particle is in the fan spray, drips are formed. Combustion chamber heat goes up, O2 sensor is read "lean" by the computer, so it signals "more fuel". Over time, carbon builds up around the injector nozzles and they have to be removed in order to clean it away. I use a 9 volt battery to open the injectors and spray carburetor cleaner threw them backwards to clean out any particles the tiny screens have trapped. It's the only way to clean injectors correctly. You can also send the injectors away to have them balanced. On 2-wheel drive vehicles, you can rebuild the front hubs, repack the front bearings with Mobile 1 synthetic gease (clear) grease the U-joints as well. Install leaf spring traction rods. I'm not sure of the correct name so bear with me. The principle here is to just have the leaf springs support the vehicle instead of using them as traction bars as well. I bought some for a big 4x4 I built several yeas ago from JC Whitney (I know what your thinking...) What they do is take away any spring wrap-up so the spring doesn't take the torque the axle puts on them. The bars are also adjustable so you can better aim the pinion to the transmission output yoke. This is very important if you've ever done this, you know exactly what I'm taling about. South-Side Machine made them a decade ago for the old coil spring GM G chassis cars (Chevelle's) They also made a bar as I'm trying to describe for leaf spring vehicles to fix the dreaded sideways jump they would do if the engine was a high powered big block. Anyway, correcting the pinion angle does wonders for forward momentum. It's nothing new and it's something I intend to do to my truck. That 454 should be getting somewhere in the upper teens. Probably the injectors need removed and cleaned is my best guess. I would do the K&N air filter also. Buy K&N filter cleaning kit and keep the filter clean, depends on how dusty your area is as to how often it needs cleaned. I clean my BMW's K&N about once every two months, I notice a differance after cleaning it. Watch the tire pressure, 10 degrees of temprature drop equals one psi of pressure drop in the tires.

FCDGMC
01-03-2006, 10:48 PM
Ryan685-
Enjoyed your advice to William and had a question or two. To start, my mileage is probably 1-3 mpg lower than it has been in the past, and my exhaust smells somewhat rich.

You mention cleaning the injectors. I pulled mine out tonight, and it's not real clear how to clean them-they appear to be a sealed unit apart from the small intake screens.

I have seen more than one person testify that replacing the fuel pressure regulator on higher mileage engines made a noticeable difference. Since I have mine off at this time, and since I'm trying to address what seems to be poor mileage, is it worth replacing or is there any way to test it? Are they expensive?

Lastly (I promise), I suspect the O2 sensor is hosed since it is badly rusted and at this point will NOT budge. Any secrets to removing this thing? It is of the one wire variety, and I suspect that it may be part of the mileage problem.

Any pointers are greatly appreciated.

Frank

FCDGMC
01-04-2006, 04:14 PM
Folks,

Ignore the previous postings in "Super Crapy Gas Mileage" from my username, a friend was using my computer. I need to know about improving gas mileage on my 1989 GMC Suburban SLE 454. I have followed a friends advice and gotten a new fuel pressure regulator, and pip coils...but is there anything else I can do to get this beast running well? I was the stupid one who put the wrong gas in the truck, and its been running offkey for the last 8 months.....getting 4-6MPG on the HIGHWAY! I miss driving my suburban, and I want to get it running somewhat economically so that I can drive it! If you have any tips at all please let me know!

Thanks,

William Stecker, The Tandy Collector
___________________

1929 Mercedes Benz SSK-Gazelle
1949 Chrysler Inline-8
1952 DeSoto Custom
1953 GMC Jimmy
1966 Volvo S-122
1974 Lincoln Mark IV 460 :smokin:
1977 Lincoln Town Car 460
1977 BMW 320i - SOLD
1978 Chevrolet 3+3 C/K 33 Scottsdale Prototype/Rarity
1978 Chrysler Cordoba (Rich Corintian Leather! :rofl: )
1979 Ford Grenada (Torque, the other white meat! :lol: )
1981 Chevrolet Luv
1982 Chrysler Convertable Prototype
1984 Chrysler LeBaron
1986 Pontiac Fiero SE/GT
1989 Lincoln Town Car
1989 GMC Suburban K2500 SLE 454
1990 Dodge Grand Caravan :loser:
1990 GMC Suburban C1500 SE 350
1991 Chevy Cavalier :cwm27:
1995 Geo Metro :loser:
And Even More To Come!

William-
Can you tell me what the advice from your friends regarding the fuel pressure regulator was? How did you or they diagnose a problem? Did you notice an improvement in mileage after you changed the part?

THANKS!
Frank

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