Rattling When Stepping On Gas?

[CSRMarc]

It almost sounds like a cable slapping around when I step on the gas, sound seems as tho it's right under drivers floor board. I thought it only did this when towing, but it seems to do it when not towing as well, not as bad though.

Any thoughts on this. Seem like it's really under powered. It's a 04' with a 5.3 with 3:42 gear ratio. It only has 41K mi. and I'm lost.

Please Help!
I'm about to take it to the dealer,but trying to safe a lot of money if it's something simple.

Thanks,
Marc

 

[Dr. Overkill]

Might be pinging... Try upping your octane.
_dennis

 

[Whipple1]

The way you are describing the symtoms it sounds like detonation(engine ping) that can give a rattle sound while excelerating and worse under a load,It will also under power the truck big time,Try putting some high octane fuel in,or go to autoparts store and get a bottle of octane boost (NOS brand), cheap gas will make this happen,Have your fuel filter changed and fuel pressure checked,Not really sure if this is what you hear but its a possiblity and worth checking.

 

[CSRMarc]

Thanks guys, I'll put some octane booster in it today. I bought it and the dealer had it for 21 days, and a few of those days were very humid.

I sure hope this works.

Thanks again guys, I really appreciate it.

 

[CSRMarc]

I put some octane booster in it. If this is the problem then it must have some bad gasoline cause this is a flexfuel Tahoe.

 

[Dr. Overkill]

I put some octane booster in it. If this is the problem then it must have some bad gasoline cause this is a flexfuel Tahoe.

I don't know what bearing it being a Flexfuel would have on this.

For more info, this page looks pretty good:
http://www.misterfixit.com/deton.htm

You're not going to be able to try some of the suggestions (eg, retard timing, reduce compression etc) but there are a few other ideas worth looking into if the octane doesn't do the trick.

_dennis

 

[CSRMarc]

Dr. Overkill I appreciate the link. I read through it and a lot had to do with the engine running hotter than normal. My Tahoe actually runs a lot cooler than my Sierra did. The temp gauge never hits the 210 mark, even in 105 degree weather towing my trailer.
I sure hope that the engine isn't getting tore up. I put some Lucas injection cleaner in it.

I'm about to take it to the dealer, I really need it for work everyday.

Thanks,
Marc

 

[tnezukon]

Not sure where you are getting fuel from but maybe you got some bad fuel. Definitely sounds like detonation to me. Im with the others, up the octane, try running premium for a while.

 

[CSRMarc]

Well I'm on my 2nd or 3rd tank since I bought it. I 've added octane booster the first and 2nd and now running fuel injector cleaner.

Just don't want to mees the engine up and end up paying more. So I think I will take it in tomarrow morning.

This thing should be running like a champ, but isn't. I sure wish I would have test drove it a little longer.

 

[tnezukon]

The only other thing i could think of would be that the igniton timing is off. I dont quite know how the ignition systems on these work. boost or jenna bear may be able to give you a better insight on it.

 

[CSRMarc]

I appreciate it, looks like I'll take it to the dealer. They chrage $90 just to look at it, but atleast it will go towards the repair.
I just can't take a chance especially since I use it to tow my work trailer.

Thanks for your help.

Marc
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[matt14]

I appreciate it, looks like I'll take it to the dealer. They chrage $90 just to look at it, but atleast it will go towards the repair.
I just can't take a chance especially since I use it to tow my work trailer.

Thanks for your help.

Marc
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Damn only 90$. Is that for a hour of diagnosis at a dealer? if so where do you stay. i work at a dealer and we charge way more than that! even at the gmc dealer, there hourly rate has to be at least 130.

 

[CSRMarc]

Damn only 90$. Is that for a hour of diagnosis at a dealer? if so where do you stay. i work at a dealer and we charge way more than that! even at the gmc dealer, there hourly rate has to be at least 130.

It's for the diagnosis period. But I'm always nervous taking my vehicles anywhere. You're in Cali, I can see why it's a lot more. I'm in the Dallas, Tx. area.

He test drove it with me in there and I specifically told him it happens in higher gears and low rpm's or at lower speeds.
He continuously felt the need to put the peddle to the floor. Man that ticks me off.
I told him that it's not in low gears and at take off. How irritating.

I called and they said it was a exhaust leak but they are trying to determain where. Huh??

I told him so it happens in gear while driving, but when he had it in park revving the snot out of my Tahoe, nothing?? Come on, it doesn't do it when the truck is in park, if it were to have an exhaust leak wouldn't it do the same thing whether in park or driving?

 

[tnezukon]

Yea I would think it would do it when it park while revving. It really sounds like detonation to me. Im no GM mechanic though. Higher gears at lower rpms is when its really under load and would be the most vulnerable to detonation.

 

[CSRMarc]

Yea I would think it would do it when it park while revving. It really sounds like detonation to me. Im no GM mechanic though. Higher gears at lower rpms is when its really under load and would be the most vulnerable to detonation.

So this would mean the timing may be off, correct? This is only my 3rd tank of gas I've ran through it, but after reading that article I figured it would be best to take it in to correct it.

Well I called them again, now they have it on the lift with the brake on and revving it to try and duplicate the noise? What??
I again told him in low gears it does NOT do this! I don't understand, maybe my communication skills are poor, but even the guy who test drove seen it doesn't happen in low gears.

Well I figured the GM dealer would have seen this before and know what the problem was.
I sure hope the Tahoe isn't worse off than when I took it there this morning.

He assured me it wasn't pinging, but if it is, what can be done to fix the detonation?

 

[Dr. Overkill]

Still think it's pinging based on your descriptions, but if you've run higher octane and that didn't solve it (or at least diminish it), then it's either a REALLY bad ping or it's something else, like the dealer said. An exhaust leak *can* sound like ticking, but I'd expect to hear it more often, rather than when it's under a heavy load and heavy acceleration. Curious to know what the dealer ultimately does to fix it. With computer controlled engines nowadays, there isn't much left to tinker with like in the old days where you could play with the timing, fatten up the jetting, etc.

_dennis

 

[CSRMarc]

Well it came down to them keeping it over night so they could get a true cold start on it.

Conclusion, exhaust leak where the header meets the pipe. I gave them the fo ahead to replace both gaskets, I just hope they did.
Parts $28.59
Laboer $225.99
Total= $281.94

I appreciate all the help and very thankful it wasn't pinging.

 

[tnezukon]

Keep us posted

I hope that fixes it up, dude. Didnt mean to scare ya. Your descriptions just made it sound like detonation.

 

[CSRMarc]

I hope that fixes it up, dude. Didnt mean to scare ya. Your descriptions just made it sound like detonation.

I was worried cause from my discription it made it sound like that to everyone I talked to. IMO it wasn't running up to par either.
And heck, it was driving me up the wall. lol

But it fixed it and maybe this thread will help and ease others with the same problem.

But I do appreciate all the help and input from you and everyone here.

Thanks,
Marc

 

[Dr. Overkill]

Glad that fixed it up. A mysterious detonation would have probably cost many more $s in the end...

I had an exhaust leak at the header a few months back, due to a misfire causing my catalytic converters to plug up and the backpressure just overwhelmed the header gasket. I could hear a distinct ticking sound from it when the engine was cold but as it warmed up it went away--the metals expanded and plugged up the hole.

_dennis