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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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What is this discussion about? GMC Sierra 1500, Chevrolet Silverado 1500, Fuel System, Truck

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#55 of 106 AFM question by jboehm Jul 29, 2008 (12:50 pm)
I have driven a couple of different Silverado/Sierras with the Acitve Fuel Management. One thing I have noticed is that, when sitting at a stop light, the AFM will switch from 4-cyl to 8-cyl. Can someone explain why? (I know that I have seen documentation that that is the way it is suppose to work but I cannot locate a reason why). Replies to this message: tafid (Jul 29, 2008 3:55 pm)
#56 of 106 Re: AFM question [jboehm] by tafid Jul 29, 2008 (3:55 pm)
Replying to: jboehm (Jul 29, 2008 12:50 pm) I have the same problem. I notice that the rpm increases as well. If I stop, open the garage door, ease off the brake, occasionally the truck will surge up to 900-1000 rpm. Chevy tech service says it is normal, but did not explain why. How can it be normal to have your foot on the brake and the vehicle rpm increase and vehicle surge forward?
#58 of 106 Re: 2007/2008 Sierra Active Fuel Management Problems [johnnyell] by obyone Jul 29, 2008 (8:24 pm)
Chinese multilevel marketing? Give me a break. Spam by any other name is still SPAM!!
#60 of 106 valve lifter noise by astroman2 Jul 31, 2008 (3:08 pm)
I have a new 2008 Sierra with 5.3l engine and about 2,000 miles. Once every week or two, when starting the engine, it sounds like none of the lifters have oil in them. The engine sounds like an old model V8 with mechanical valve lifters that are way out of adjustment.   The valve clatter will continue but goes away by shutting off the engine and Immediately starting it again. The oil pressure is good and the dip stick shows oil is full.   The noise only happens when the engine is cold or warm. Is AFM in control of the lifters and valves at startup?   Has anyone had this problem?   Thanks, Replies to this message: natesms (Jul 31, 2008 6:18 pm) rednecktroy (Sep 28, 2008 4:27 pm) obyone (Jul 31, 2008 8:34 pm)
#61 of 106 Re: valve lifter noise [astroman2] by natesms Jul 31, 2008 (6:18 pm)
Replying to: astroman2 (Jul 31, 2008 3:08 pm) I have the 6.0 in my Silverado and I have noticed that to, but very breifly on start up. It sounds exactly like you describe but goes away in a couple of seconds. I don't have to shut it off and back on.   Let us know if you find out anything. Replies to this message: rednecktroy (Sep 28, 2008 4:27 pm)
#62 of 106 Re: valve lifter noise [astroman2] by obyone Jul 31, 2008 (8:34 pm)
Replying to: astroman2 (Jul 31, 2008 3:08 pm) The dealer will tell you that this is normal and happens more often with the 6.0 for some reason. For myself, it would disturb me. But what can you do?
#63 of 106 New Sierra & AFM by raymaz Sep 23, 2008 (6:13 pm)
I have the 1500 5.3 with AFM and have noticed an inconsistent vibration at about 55mph. There's a flat smooth stretch of highway I often take going home for about 7 miles and the vibration often occurs there between 50 and 55mph. It feels like I'm going over a course road surface but I'm not. AFM is sometime on and sometimes not. This vibration always occurs when I maintain this 55mph +/- speed for a time. It never happens in town and I have never noticed it at 65+. I've never ntoiced it at idle. Other than that I like the truck a lot. I'm a boring old fart of a driver but I get very good mileage. The lowest fillup I did gave 16.6 and highest has been 22.4. That 22.4 was almost all highway driving. Considering the power and size of this truck I think that's superb. Replies to this message: obyone (Sep 23, 2008 11:54 pm)
#64 of 106 Re: New Sierra & AFM [raymaz] by obyone Sep 23, 2008 (11:54 pm)
Replying to: raymaz (Sep 23, 2008 6:13 pm) 50-55 mph is where most of the resonances in a vehicle converge for some reason. That's why there's no vibration at 45 or 65 but keep it at 55 mph and you've got a bumpy ride. This is usually attributed to the tires.

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