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Pickups Chevrolet Silverado & GMC Sierra 2007/2008 Silverado and Sierra Active Fuel Management Problems
106 messages, Last post on Sep 01, 2009 at 9:04 PM
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This is my 5th truck which I ordered from the dealer in Maryland and picked up in January 08. After driving it about 200 miles I proceeded to drive to Ft Pierce, FL non stop. Generally speaking, I drove 5 to 7mph over the posted limit e.g. in a 55 zone I drove up to 62, in a 70 zone I drove up to 77.....almost always on 'cruse control'.......my average for the trip was 18.4 mpg and the truck performed flawlessly. I now have 6000+ miles on the truck and it consistently 'averages' in the 16-17 area (mostly short 'around-town' runs). I find that the AFM is NOT noticeable by passengers but IS noticeable by me....though now I find I'v become oblivious to it!! This truck is a 5.3L, 4X4, LTZ with Stabilitrak. My last two trucks were a Dodge 2500 Diesel and a Chevrolet 2500HD Diesel respectively.......this '08 truck is far more economical than the Dodge and equal to the Duramax, though, I'm sure, it won't tow as much....its all a balancing act....the diesels are a $10K additive cost and the diesel fuel is 12 to 15% more expensive than regular......bottom line is that if you are not towing high weight trailers frequently it is far better to go with the gas truck! Prior to the Diesels I owned a Nissan and a Toyota.......wasn't happy with either of them!! |
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I have a 2008 chevy silverado with a 5.3 and active fuel management. I am wondering if there is a way to tell when the truck is running on 4 or 8 cylinders. Can you hook up a test light or something to that effect,
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| I have heard that there is an issue with the Fuel management system when you put on a duel catbak exhaust. When it shifts to 4 cyl it makes a roaring sound? is this true and if so what luck has anyone had with finding one to put on an 08 silverado 1500? | |
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Replying to: tomkronberger (Apr 06, 2008 7:02 pm) |
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Replying to: canw (Jan 21, 2008 8:28 am) How can you see a difference in what you get as far as every day performance? I suggest you run the crap out of it occasionally. Also, if you are always running regular fuel, don't. Run a tank of premium or mid grade through her every so often. Or just add some to your regular. Right now no one offers a cold air package for them. K&N has a drop in replacement that helps. Few tuners out there too. Hypertech seems to be the best. Diablo just came out with theirs. Gibson has a great cat-back exhaust that helped mine. Sounds great without a lot of in-cab resonance. These alone have helped improve the mileage. But if you are like me you may not be able to keep your foot out of the throttle. I LOVE THIS TRUCK! If it didn't have a speed limiter (at 95) I bet it would pass 150. The AFM system only kicks in under the lowest load conditions. Down hill, tail winds, flat road. When on the highway try setting your cruise control just as soon as you feel it go into overdrive. Set with RPMs at 1500. Should be on 4 cyl. Look at your DIC. Should say somewhere around 24 mpg. Also around 45 mph. But most people can't stand to drive that slow. I can't. So I just drive the way I feel, within the law. HA! Anyway, don't treat that truck like a baby. It aint! You wondering when it'll break in? It wont until you use it. So use it.
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| You have afm,no dic installed,noway to tell if afm is working.For 17,000 miles I complained about really bad economy.Finally the lifters started tapping took it in for service the world class mechanic told me [they all do that piston skirt knock]I argued till he finally listened to the lifter tap.they replaced lifters plugs and wires.reprogrammed the computer,now I'm getting 20 to 24 mpg.But it has developed a mind of its own sudden accellation at stop rpm's raise from 500 to 1200 not all the time just every once in awhile.,\gm tech can't reproduce the problem,gave it back to me and said wait till it does it more often.Had a tick in the windshield,was told the bug deflector was the problem took it off still had the tick,they replaced trim inside the cab.Gas guage was saying less gas in tank,replaced a sending unit,fixed that,then a valve for the evap canister went out,fixed that.Of course I have called gm to,ask for compensation for the 17000 miles of 8-9 mpg they said no,I asked for the dic button to be installed,they said that is a dealer option,dealer said"As long as it does'nt cost more than a$100,they would cover it.Why would they say you have afm but no way to show it working,cuz they get $600. for it free,I have 87 chevy sitting in the garage it does a 11 second 1/4,at 112mph in four wheel drive,I've built a bunch of bowtiesbut this 2007 silverado has yet to impress me,nor has gm at this point. | |
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Okay, so this may be heresy but active fuel management is the new hype for most cars and trucks. I was looking at buying a new GM, preferably the hybrid Silverado when it hits the market but quite frankly I can't afford a LTZ model (which all hybrids come in) and I can't seem to sell my 1998 Jeep Cherokee 4.0L. So an idea hit me: why not put active fuel management on it. The proposed plan is to hook up a simple 5V programmable computer chip to 6 relays that shut off selected fuel injectors at 5 minute intervals (Just like Chevy does on its 8 cylinders). This is to operate the front three cylinders then the rear three cylinders intermittently. Its about a $75 dollar system once the relays, wire and board are purchased and about a 4 hour installation (3 hours of which is required for programming the C++ style board), but the hope is to see if active fuel management really makes a worthwhile difference in highway travel. Right now I achieve about 22 mpg highway (10 city) and have hopes that the old beast can get a few miles more per tank. Will keep you updated on whether or not active fuel management makes a difference on highway travel or if its something we pay more for from factory but get nothing for in return. Personally, a Prius doesn't sound too bad... if you like 76 horsepower and the ability to tow nothing.
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Replying to: mattbarry6 (May 29, 2008 6:09 am) AFM always turns off the same valves though. It doesn't alternate. It also turns itself off after 5 minutes of continuous use to prevent the active cylinders from overheating to much. In any case, this is my reading forums only. My 5.3L AFM is bone stock.
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Replying to: branhap (May 29, 2008 8:19 am)
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Replying to: rednecktroy (May 30, 2008 4:28 am) As for tunes, the most popular one I read about is black bear tune. He basically sends you some equipment to plug into your truck, then you send him back the info tell him what ya want and voila. gm-trucks.com seems to have the most info on tuners. Good luck! Paul |
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