Piston Slap Story in the Detroit Free Press

[Greg]

From today's freep:

 

http://www.freep.com/money/autonews/knock1...14_20031114.htm

[LogixRat]

Sounds like a few folks have finally had enough. Like many others, I love my truck but wish it didn't have the "rattle/knock" under heavy acceleration. Too many of my friends and people everywhere have had this problem. I think GM needs to take some responsiblity for the matter, instead of ditching it as common noises.

 

I was suprised at GM's willingness to buy back vehicles, albeit at the expense of using an attorney to accomplish the matter. My problem is I love the 99-02 body styles. The nose on the 03's just haven't grown on me enough to want one. Can't they just replace or fix the engine?

[99GMCZ71]

Funny thing is, i have yet to hear the knock in my 1999 5.3. Knock on wood i guess.... no pun intended

[gmcjoe]

Interesting story, glad this is finally getting the exposure it needs.

 

I will say statements like this one "I paid almost $35,000 for this truck. The truck is almost worthless," are a bit blown out of proportion.

 

My 2000 5.3l has the 'cold start knock, piston slap, whatever' and I have 96k trouble free miles on this engine...

[RyanbabZ71]

this is all i need to know

 

"Current analysis of 150,000-mile and 300,000-mile engines that have exhibited cold start noise show no significant wear," Read said.

 

good enough for me

 

I dont know about that guy who wont take his truck to upper michigan and will only drive it to work. He sounds to paranoid. Maybe if he drove it more it wouldnt knock. Its been in the low 30s as of late and mine has been silent. Last time it has "knocked" was in sept.

 

I cant believe GM is paying 40K for these trucks. Maybe i need to contact a lawyer then i can buy myself a brand new truck

[TROYROBO]

maybe if some of these people would blow the cobwebs out --this might not be happening---mine has never had a ping or knock--just a lifter tap at startup that only lasts for about 10-15 seconds--with about 80000 miles on it-and yes i keep my foot in it regularly--would buy several of these trucks if i had the funds - if you know what i mean

[Z71GUY]

Yep, I run the crap out of my truck.... its a 99 with 5.3 & 46,000 miles.... no knock at all... runs great!

[LogixRat]

Hehe, with a 5.3 it's hard not to run the crapola out of your truck. Sometimes I'll just be 'cruis'n' along the highway, look down and I'm runn'n 85-90. The truck just glides down the highway. By far this is probably the best vehicle I've ever owned. I think that's why I wish GM would issue a fix for this problem, and finally acknowledge it IS a problem.

 

As much as I like my truck, there is nothing any more sickening then hearing the engine sound like a rod is gonna shoot through it when I hit the gas to pass someone. The cold knock at startup isn't so horrible on my truck, but the "rattle" drives me nuts. For me, I don't really intend to get rid of the truck for many, many years (hopefully LONG after it's paid off).

 

Who knows if I'll be in the 150-300k range or not, but I realize if the pistons are out of whack and wearing weird then it is causing a LONG TERM problem that I may experience if I decide to keep the truck around for years to come. I could careless about GM paying my truck off and any cash in my pocket. Instead I'd just rather have a better built engine that won't have that long term effect.

 

Overall I feel mine is much minor compared to other friends. One has the problem so bad that people frequently ask him if he has a diesel engine in his truck. That is sad, and in my opinion the responsibility of GM to make right. Oh well, here's to hoping that GM will issue a recall or fix or something.

[Markeaux]

As much as I like my truck, there is nothing any more sickening then hearing the engine sound like a rod is gonna shoot through it when I hit the gas to pass someone. The cold knock at startup isn't so horrible on my truck, but the "rattle" drives me nuts.

Have you tried a higher octane gas? I always run 93 and never ever get any pinging, but I do if I drop down to mid or regular grades.

[k1500chevy97]

This is a serious problem that gm is trying to cover up by saying its normal and i think that all the "knocker" owners should take this to court and not let gm get away with building crap

 

So yours doesnt knock so they all dont I guess? Everyone on various web sites news papers tech articles is lying then?

 

Face facts. Some knock and its unacceptable.

 

As a current happy gm owner i would not buy a vortec V8. I would either buy a V6 again or the Dmax. I sure wouldnt take the gamble or to be stuck with a POS slapper.

[ctoliver]

good old gm has an answer for everything telling people that the knock is ok but i can tell you my truck does not have the same power it did when i first bought it. my truck knocks when its cold csk (started at 13,000 miles) and when it warms up. two different knocks. this is my theory and would love to hear your thoughts on this, like i said my truck has no power i was wondering if with this constant knocking situation i have if this is causing all my pinging problems its like the knock sensors are picking up this and keeping the ignition timing messed up. just a thought i have tried everything from trying every brand of gas to checking all related sensors all appear to be working like the manuals say they are suppose to, no check engine light never and no stored codes, replaced fuel filter several times and had the injectors flushed, did the tsb on the knock sensors. the sensors i pulled out where fine checked good but put new ones in any way. my fuel economy has dropped was 18 to 20 mpg now if i get 16 im doing good. removed my k&n air filter and put back the paper cause the oil was getting on my mass air flow sensor that i have cleaned numerous times. i dont know what else to check! im fed up with this gm crap. dont get me wrong i love my truck but gm needs to step up and address some of these issues, there are other issues with the truck but i have learned to LIVE with them and we wont get into that right now. ok thats my rant i feel better now let me know what you think!

co

1500 4.8l 75,000 miles

no mods all chevy

[LogixRat]

Have you tried a higher octane gas?  I always run 93 and never ever get any pinging, but I do if I drop down to mid or regular grades.

I've ran 93 in the past a time or two, but not since noticing the "rattle/ping". I was talking to another buddy this weekend, and he said his GMC was doin the same thing under strain (he pulls alot). And he reported good success with running the 93 octane.

 

On the other hand, I have another buddy that had the ping/rattle so bad that it didn't matter what type of octane he used...it just sounded awful!!! He took it into the dealership and they reprogrammed the computer. When he got it back it ran much stronger and the ping was gone. Unfortunately it came back about 10k miles later and wouldn't go away, regardless of octane grade. He finally got disgusted and traded it in for a Jeep.

 

The thing that torques me is that my truck is not a high performance vehicle that should demand the higher octane. I've owned Camaro's, Vettes, etc. in the past and they need it. I was fine with putting it in, cause it said "Premium Only". My truck don't. I'm glad it may fix it (at least temporarily) but feel this doesn't relieve GM of their problem.

 

The first buddy I noted that is running 93 with success, he works at the GMC dealership. He says they are constantly getting people in with the same problem. As we all know they are not able to do anything, and most the mechanics just feel the engine is not designed well. When the guys doing the actual work feel it isn't right, and has concern then I don't have much faith either. Suprisingly, everyone still thinks the same as I do...it's the best truck in the world if it just wouldn't knock!

 

Time for GM to suck it up, step up to the plate and do something before they start losing their loyal customer base. Any company is only as good as the product they sell and the warranty they truly service! Screw the customer, and you are all but hanging yourself.

[Markeaux]

I wonder if the gas is really the octane it says it is? That would also be one thing to check, but how I don't know.

 

Also, I have heard that carbon deposits can cause a knock/tick as well as pinging, plus the deposits can decrease the combustion chamber volume effectively making the cylinder(s) higher compression thus making regular gas predetonate (ping) and so requiring higher octane gas to keep pinging from occurring. Mr Goodwrench will do that top end decarbonizing procedure which typically fixes that problem but yes it can re-occur.

 

Has anyone had the oil pump o-ring TSB done to cure the ticking at idle?