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cheaperrooter
Body Lift
Posts:152
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| 01/31/2008 2:43 PM |
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| Ok, I found the bulletin put o |
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webby4x4
Forum Admin, Magazine Editor
Rock Star
Posts:2375
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| 02/01/2008 7:39 AM |
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Answers / thoughts below...
quote:
Originally posted by cheaperrooter
Ok, I found the bulletin put out by Chevy the dealership guy printed out for me. I am confused, mainly because I am not a mechanic, so I am lost at the wording. I am going to type it verbatim. Here we go:
Service Bulletin Id# 1859647
Subject: Rattle noise in engine (Install timing chain tensioner kit)
Models:96-03 Chevy astro, blazer, express, s-10, silverado, and P models
96-03 GMC jimmy, safari, savana, sierra, sonoma
96-01 Olds bravada
with 4.3l V6(vins W,X, - RPOs L35, LF6, LU3
(Louie: Note it doesn't say if the above engine specs is for the Bravada ONLY or all of above)
Rick - It's for all of the vehicles above, that have the 4.3l V6 engine with VINS that have the following codes within themL W,X, - RPOs L35, LF6, LU3
quote:
Originally posted by cheaperrooter
Bulletin being revised to include additional models.
Rick W - While it's not identified here, there appears that other vehicle models *can* be included in this.
quote:
Originally posted by cheaperrooter
Condition: Customers may comment on a rattle type noise coming from engine at 1800 to 2200 rpm.
Cause: The spark, rattle type noise may be caused by torsioanl vibration of the balance shaft.
Correction: If detonation is present, perform detonation/spark knock diagnostics first.
Rick W - The key word here is "torsional vibration". This can be certainly be caused by detonation (pre or post). This can be caused by a number of variables in the engine (sensors, timing, poor tuning, etc.), but a timing chain that has too much slack, will change the timing erradically.
quote:
Originally posted by cheaperrooter
Install a new timing chain tensioner.
Louie: Ok, the rest is how to instructions. I am confused because I cannot figure what a timing chain tensioner kit rattle has to do with a spark, rattle type noise. Its almost like its saying there are 2 different causes of this. One is a detonation noise, which can be fixed WITHOUT this kit.
Rick W - I would think that this is an "and", and "or" situation. To put it another way, they can be, but don't have to be, mutually exclusive of each other. So... a timing chain that has slack can cause the rattle (stuff just banging around), AND/OR it could cause the timing to shift slightly which could cause spark detonation, which can also cause the sound. make sense?
quote:
Originally posted by cheaperrooter
I need someone to make heads or tail out of this for me. The guy who replaced the chain said it was probably fuel system related as these trucks run lean, and to add some Lucas fuel conditioner to my tank. If it didn't work, do an injectore cleaning. I do not know why, but I just feel like thats not gonna work. Its a loud rattle. Also, for what it worth, after further diagnostics, since the new chain was installed, the rattle noise has a HIGHER rpm range then before. Before it cam on around 1500, now it comes on around 2000 PLUS.
Rick W - At first I thought this was peculiar, then I started thinking about the dynamics of it. A new timing chain will be different than the old one, as it will be tighter. It may be, that those engine blocks have a slight issue with the tolerances of the cam-shaft opening and/or the crank-shaft location. What I mean is that there may be a 100,000th of an inch tolerance variance, which will cause timing gears (and subsequantly timing chain) variances, which in turn can cause a slack timing chain. Not a big deal, but something I was contemplating.
quote:
Originally posted by cheaperrooter
Thats why I thought it went away the other day. I just needed to rev it a little higher. So the chain effected it in SOME WAY. Any input would be nice Guys. I know you all are the best in the world at this stuff. <-----Blowing smoke your way for HELP
It sounds to me like you may want to consider the timing chain tensioner. This is a peculiar problem indeed. You may consider having a local mechanic install the tensioner kit, as it will save you a lot of money, vs. if you took it to the dealership.
Hope that helps clarify a bit.
Rick |
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Rick Webster
Editor, 4X4REVIEW.COM - A Tork Media, Inc. Publication
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'74 FJ40 Land Cruiser
"Measure once, cut twice" |
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cheaperrooter
Body Lift
Posts:152
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| 02/01/2008 3:32 PM |
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Correction: If detonation is present, perform detonation/spark knock diagnostics first.
Louie: So Rick, They DID not do this test when I brought it in. I know. I watched them. They had 3 techs hovering around it, trying to find its source. But that was it. I mean seeing as how I already have a new timing chain installed, the big question of the day would be do you think there is another way to correct this problem? I mean the new chain could only be so slack. Is there any other way, with new chain installed, to correct pre or post detonation?
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webby4x4
Forum Admin, Magazine Editor
Rock Star
Posts:2375
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| 02/01/2008 4:02 PM |
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sure... alter your timing. Have you done that yet? I've been assuming all along that you've had a tune-up, and had it put on the diagnostic machine.
Rick |
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Rick Webster
Editor, 4X4REVIEW.COM - A Tork Media, Inc. Publication
- - - - - - - - - - - - - - - - - - - - -
'74 FJ40 Land Cruiser
"Measure once, cut twice" |
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cheaperrooter
Body Lift
Posts:152
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| 02/01/2008 6:10 PM |
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| NO.....No....No. I brought it the dealership to fix rattle. First they replaced idler pulley. I picked up the truck, and immediately heard it. I drove it RIGHT back. They brought it back in while I waited and said it was Catlytic converter. I drove home. I listened to it when I got home. I said it wasnt. I called Dealership and complained to Service Manager. I brought it back, 3 techs hovered over it on the racks and then they printed out that bulletin. That was it. He said timing chain. $1700 I went on this site, and you know the rest from there. I found a guy to do it for barter. Its done. I still have the rattle. (by the way, rattle now seems to vary. Earlier I told you it shifted to over 2000 rpm. Well that was when I power braked it. Now, for some odd reason, it does it at 1500 IDLE. It would appear its all over the place as far as rpms are concerned, whereas pre timing chain install, it was very consistent rpm wise) Anyway, No tune up has been done, though I ASSUME the guy who put in timing chain HAD to adjust the timing, right???? |
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webby4x4
Forum Admin, Magazine Editor
Rock Star
Posts:2375
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| 02/02/2008 8:30 AM |
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quote:
Originally posted by cheaperrooter
though I ASSUME the guy who put in timing chain HAD to adjust the timing, right????
Technically, you don't have to. You can just rotate the engine until the dots align on the cam and crank gear sprockets, then remove and replace from there.
Rick |
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Rick Webster
Editor, 4X4REVIEW.COM - A Tork Media, Inc. Publication
- - - - - - - - - - - - - - - - - - - - -
'74 FJ40 Land Cruiser
"Measure once, cut twice" |
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