not denouncing what you say may be the prob but you seriously are saying its not the engine itself?? I know its funny that it only happens at high rpm i figure if its a tap or knock i would hear it at low rpm as well. I was told maybe a bearing prematurely wearing???? I just find it hard to believe that its an engine related prob which you are making clear for me that its not.
Hearing from you that the cats already went and this noise only happens under load makes me wonder if you have a carbon buildup and what your hearing is actually detonation. Knocking is never good and I strongly suggest you do find the problem promptly before driving it much more.
Not to get off track again, but I raced (this was a race) a Tahoe from a light onto an on-ramp. I won! (Then again, it was wet out and the guy in the Tahoe gave it a little too much gas on the turn and spun the truck... apparently a lifted, unblown 80 is a threat...)
ben, then you think at 51k miles this could happen in terms of carbon buildup?? But i never hear anything at idle or under load up to 3k rpms. The engine runs so damn smooth, and i have been driving the tuck, (not flooring it) for a while like this with no problems at all. Its just weird that this damn noise happens only when the engine is winded up over 3k rpms and only when the engine is warmed up. Should i run some fuel cleaner??? I just changed the plugs about a month ago and i think that this noise started after i changed the plugs if i think about it, could that have anything to do with the sound??
ben, then you think at 51k miles this could happen in terms of carbon buildup?? But i never hear anything at idle or under load up to 3k rpms. The engine runs so damn smooth, and i have been driving the tuck, (not flooring it) for a while like this with no problems at all. Its just weird that this damn noise happens only when the engine is winded up over 3k rpms and only when the engine is warmed up. Should i run some fuel cleaner??? I just changed the plugs about a month ago and i think that this noise started after i changed the plugs if i think about it, could that have anything to do with the sound??
Unknown, as I haven't heard or seen your truck. Ping isn't common at idle but it can happen at any speed under load, so obviously I'm only guessing based on what facts you have stated. How did the old plugs look? Cats should not just go bad that soon without something else in the mix. It sounds like you might not push your engine very often which can lead to carbon buildup. Fuel system cleaner can't hurt but if your engine is carboned up bad just running cleaner through it probably will not clean out much deposit. There are more aggresive ways to loosen up carbon without teardown (i.e. Seafoam soaking treatment, etc..) but if the carbon buildup is really that bad you could actually cause other problems from chunks getting stuck on exhaust valves/seats and also lodging in the screens of those new cats. If this seems like it might be over your head spend a few bucks and have a professional take a look. A few bucks now could save lots of bucks later! Something you might try is retarding your timing 2 or 3 degrees and see if the noise stops. Also switch to premium fuel for a whole tank. It really is impossible for anyone to tell you exactly what the problem is without hearing the noise first hand.
I hear you on that pint about hearing to find out the problem. I will try seafoam engine treatment immediately. I never really get on the motor at all until these past few days becuase of the noise to try to hear it better.
I hope the seafoam does the trick we shall see.
The oil pressure is perfect, there is no smoke from the tailpipe when i floor it at all.
I also see in the manual that when at high rpms underload you will hear some pinging or knocking sometimes. Mabey its the fuel, i use 89 in New York but that may be watered down with some methanol more than supposed causing this problem.
I will do a list and check each thing out as i go to find the problem.
Old plugs looked a little used, no major blackening or anything weird.
When my cats went i heard a rattleing noise from them like they were breaking apart.
Let me ask you this real quick. What can tick louder as the rpms go up under load in the emissions system (egr, vsv...etc...)?? I am thinking it has something to do with the EGR valve for some reason becuase of what happened when i blew my cats and drove for 120 miles.
A trick to try and hear it more is to drive the truck with the window down beside tunel or a highway with a tall wall. With the window down you can hear more of the pinging or cackleing under a load. If so you have predetonation for what ever reason. A 97 truck with very low miles may have been driven low miles back and forth with little warm up time creates lots of problems (little old lady truck)later in life of a engine.
Any how, the bearings are real tough and I would doubt this. On a real cold engine can you hear any sound of knock when you first start it up, If so, you may have some piston slap that is then giving you sounds when you load it up.
Good luck robbie
Antoher thought is "do you still have the orginal Y pipe from the headers to the cat?" If so some times at the Y you can have a exhaust leak that is heard usually under load more so. I have welded several of these up in the past that can create a sound you describe as well. later robbie
Hey robbie, thats exactly what i did yesterday, under a bridge and heard it when i floored it and thats when i hear it.
I do not hear it when the engine is cold under that load,
I do not hear it when the engine is idleing or under load before 3k rpms.
I do hear it when the engine is at maximum temp and reved 3k + thats the only time it shows its head.
I can hear it when i rev the eng to 3k+ at idle with my finger pushing the throttle.
When i floor it at like 40mph and the engine revs out past 3k i do not hear it that much at all.
i tryed pressing the power button today and just giving it some more gas than i usually do and i heard it faintly when it revved over 3k. Very Very weird.
Its a ticking noise but it does not sound muffled at all, more like its causing damage noise. Metal or pressureized air noise.
I still do have the original y pipe.
No performance issues at all, the truck runs like its new literally! My last LC had 130k miles on her before i sold her and you could feel the truck needed to have a major engine cleaning (carbon build up) performance was so so but never heard anything like this before.
No hesitation, no missfiring, no cel, nothing that would make you think its something bad prior to hearing the noise at 3k+ rpm.
Mabey belts, mabey exhaust manifold, maybe one of the bearings are pre-maturely going bad??? I dunno but for it being an LC and the low low miles i highly doubt its any kind of engine problem.
without hearing the sound it is difficult to really understand the situation. However, this make it sound like it is not occuring under load. Does teh sound or occurance change if you are pushing the throttle with your finger in your garage or WOT up a steep hill? ho about from a stop vs 40mph mash of the skinny pedal?
"I can hear it when i rev the eng to 3k+ at idle with my finger pushing the throttle.
When i floor it at like 40mph and the engine revs out past 3k i do not hear it that much at all."
I would do as mentioned put some premium gas 91 octane and see what happens sounds like a detonation issue to me.
I will try what you say speyrod, i filled up with 89 yesterday so i will have to wait after that tank. I do hear it when i mash the skinny pedal from a dead stop thats how i heard it the first time. at a rolling 40mph when mash the skinny pedal i hear it but faintly compared the dead stop.
I will report back after i have done so.
Any more info that anyone has with simular experiances please post some info in what you may think the problem may be.
Sorry to revive this thread, but this happened on a friend of mine's truck this weekend. We were out wheeling and he hit his exhaust and caused the stock muffler to hit the driveshaft where the shaft and the yoke meet. It only happened when the engine was being torqued like on uphill climbs or under semi-hard acceleration. We haven't fixed it yet but plan on it soon. Hope you've already figured this out but if you haven't hope this helps.
well its still there but the truck runs mint. I dunno, i think there is a micro crack in exhaust manifold and its causing the tapping noise. I am going to bring it to the toy dealer when i get a chance to get it checked out.
What's the history on this truck? By that I mean to say I'm innately suspicious of an extremely low mile Cruiser. Makes me wonder if it was hit in 99 and sat in a wrecking yard for 5 years, then was rebuilt into a saleable vehicle. Ever do a Carfax? Was it the VERIFIED original owner you bought it from?
I base this on the cats going bad, and now a mysterious noise - all tips that things may not be as they seem....
If it's still running fine, then I'd focus on the exhaust mans.
well its still there but the truck runs mint. I dunno, i think there is a micro crack in exhaust manifold and its causing the tapping noise. I am going to bring it to the toy dealer when i get a chance to get it checked out.
First place to look at is the joint in the front pipe where it splits to the two manifolds. It usually cracks on the block side so when the engine is cold have someone start it up and rev it while your hand is behind there. This is how I found mine.
The truck was verifyed original owner, i have the original window sticker and the original purchase agreement with his signature on it, the whole bit. Carfax is clean and all checks out a++. I am going to do a seafoam to the fuel system and see if that cleans things up.
Idaho, how do i do the seafoam, by directions on lable or is there a special way with these motors??
