2003 4WD trailblazer knocking

Greetings,
I took my trailblazer to the dealers to get a few things straightened out, The back panel around the license plate rubber gasket was pulled
in, probably installed too tight. they installed a new seal, problem taken care of. I also told them of an engine knock, sounds bad sometimes on startup, sometimes no knocking at all, of course, when I took it to the dealer it would not knock for them, they told me that they reprogrammed the power train controller module. I got in and started it up, knocking was loud, drove it around to the service entrance and, sure enough, they heard it. Glad that they heard it, funny how problems disappear when at the shop. Had to make a new appointment, said that it was possible piston ring slap. I use Mobil 1 oil and was wondering if it could be oil related. They are a great bunch of guys at the dealership, however, I hate to see them tear into the engine if they do not need to, it has only 33,000 miles on it. I was wondering if there are any TBA's out for this sort of knocking problem. It sounds like a collapsed lifter noise, it starts knocking as soon as the engine starts, doesn't have to be in gear. Could it be a failing injector?
As always thanks in advance,
Markus
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I have the same truck, had piston slap from day one as many of todays engines of all makes, if it goes way in a few minutes this usually the problem, but this is for the shop to determine and advise you accordingly.

-
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Several 2002-2003 owners of TrailBlazers/Envoys/Bravadas have experienced this same problem--and some of them have had to get GM regional reps involved in order to get their engines replaced. In cases where the engines weren't replaced, the owners were given warranty extensions up to 100,000 miles. There are myriad explanations for this problem floating around various GM circles. The most common one is that the aluminum block engine uses cast iron cylinder sleeves and the pistons have a special coating on them. Sometimes fragments of the cylinder sleeves break loose and cause extensive engine damage. Certain GM reps claim that the type of pistons that are used in the triplets are what causes the piston slapping/knocking sound--especially at startup. My 2002 TrailBlazer LTZ did it too. I first noticed it one morning at Myrtle Beach, South Carolina when I started my SUV for the wife and I to head out to breakfast. They extended my warranty to 100,000 miles after I complained about this problem multiple times, but I ended up unloading the vehicle not too long after they did this. Mainly due to the vast number of other issues that I had already experienced with my TrailBlazer. I was just fed up with mine.
Ron M.
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Ron,
Took it in they gave me a loaner car, want to tear the engine down. The noise is pretty loud especially at startup, sounds exactly like my old 1981 Chevy station wagon that had a bad lifter. I dumped that car after it was repaired, just didn't 'feel' right after the repair and I got fed up with taking it back. Hope that this beast fairs better.
Thanks again,
I'll keep you posted as to what transpires,
Markus
wrote:

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does the knocking continue after a few seconds or does it stop. if it stops it is the lifters loosing prime. no fix availble yet per gm techline. if it persists it could be a sign of internal engine dammage. how loud is the noise. if you cannot hear it over road noise and slight volume on your radio gm will tell you it is within acceptable tollerances. you can try a can of a product called EOS available at the dealership (engine oil suppliment)that sometimes helps in this situation.
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Some on this NG have had engines that were prone to lifter noise with certain oil filters. Even Delco's. I'd try a Wix filter and see if the noise goes away. I'm not suggesting that this is your problem, but it is a possibility.
Dave
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Hairy,
When I get it back I'll change the oil and put on a WIX filter, Thanks for the info. I had a WIX on it just before this last change, put on a NAPA Gold 1522 this last change, have been running Mobil 1 in it, just can't seem to break down and start running AMSOil because of availably and cost.
Take care,
Markus

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Napa golds ARE WIX filters w/ a different paint job. For startup clatter, I've found that purolators are better at stopping it at least in my '88 K2500.
-Bret
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Bret Chase wrote:

    If a Brand of oil filter clears up a engine noise, you are suffering from Low oil Pressure when cold/Ambient Temps.
    This means sooner or later you will have a Dead engine. Charles
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On Thu, 25 Aug 2005 07:01:49 GMT, Charles Bendig

um, no.
what I am referring to is the .5 sec of valve noise due to a half full oil filter. if your filter's ADBV has leaked it takes .5 sec or so to fill the filter back up. pretty common for older GM 4wd's with the sideways mounted oil filter.
btw, I have 55psi @ cold idle within 1 sec of engine start (mechanical gauge).
-Bret
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