93 Tlc Rattle Under Load (1 Viewer)

[rdye]

I have a rattle that nobody has been able to diagnose. It starts after the engine is warm and is loud when going up hills. Exhaust system, including the convertors have been eliminated as a source. You can't duplicate it on a lift or sitting at idle. It won't do it except while driving and under a load.
The 'Cruiser is running perfect and is in great shape with 138,000 miles. I am out of ideas and looking for any suggestions.
The rattle is very similar to a rattle I had in a bad cat. convertor but those have been replaced. It is much louder out the passenger windows which made me suspect exhaust system to begin with.

 

[Atticus]

I have a rattle that nobody has been able to diagnose. It starts after the engine is warm and is loud when going up hills. Exhaust system, including the convertors have been eliminated as a source. You can't duplicate it on a lift or sitting at idle. It won't do it except while driving and under a load.
The 'Cruiser is running perfect and is in great shape with 138,000 miles. I am out of ideas and looking for any suggestions.
The rattle is very similar to a rattle I had in a bad cat. convertor but those have been replaced. It is much louder out the passenger windows which made me suspect exhaust system to begin with.

I have the exact same problem. I thought it may have been the cat shield(s) but have bolstered them to no avail. I'll monitor this thread for progress.

 

[rdye]

Misery loves company. I don't even want to drive it since it sounds like a hunk of junk when the rattle starts up. I removed my cat shields.

 

[sethro]

What about the down pipe heat shields? Look in the passenger side wheel well. Mine WERE rattling...they stop rattling when they're off the truck.

 

[rdye]

They seem to be solid and look fine. I thought about taking them off. I pounded on them with a rubber mallet and couldn't get any noise out of them, hot or cold.
Thanks

 

[jaxcruiser]

i took my heat sheilds off too and my cat shield. The rattling stopped. If you want to go the extra mile buy the exhaust wrap for your headers down to where the heat sheils use to be. It reduces heat under the hood and i noticed my engine didnt work as hard it seemed.

 

[Atticus]

Any progress with this rdye?

 

[rdye]

I think I have eliminated all possible sources in the exhaust system. I am pursueing another possibility.
I have had a problem with a cold start rattle which may be related to the now persistent rattle I have. It has something to do with lack of lubrication to the timing chain tensioner on start up. I am still researching it. There is a lot on this subject if you search "rattle", "cold start", "timing chain", etc.
Apparently, a lot of people have had this problem and there are a lot of suggestions and some tech articles that I will have to get into this weekend.
It sounds like an internal rattle but its impossible to detect at idle or sitting at idle and raising the rpm's. I hear it mostly at low speeds, climbing a hill.

 

[Atticus]

rdye,
I am a little confused. It sounds like you are describing the exact same rattle I am now enjoying on my rig. Why would this rattle be related to a cold-start rattle you are experiencing if you cannot hear it at idle? Or, are you saying that it rattles upon start-up, stops once the engine warms up and is idling, and starts rattling again once you start moving under load? The reason I am asking is because I cannot imagine that a rattle as loud as the one I have right now could be coming from the timing chain without affecting performance in some noticeable way, which has not yet happened. Also, how did you remove the cat shields? The fasteners seem to be some sort of rivets on mine. Did you just drill them out?

Good luck.

Jay

 

[cruiserman]

If it's under load, maybe it's detonation.

 

[rdye]

Its an instantaneous loud rattle that last for a second right when the engine fires then immeadiately goes away. I don't hear the persistent rattle until the 'Cruiser is up to normal maximum temperature.
My cat shields had rusted bolts on all corners except one which had been welded. I removed cats because I replaced them. The new convertors, which were supplied by Kansas City Convertors, were a liitle larger with built in heat shields so I couldn't put the old heat shields back on. I tore the shields up a little taking them off the old convertors since I had to return the used ones to Kansas City Converters.
There were several pebbles in there. I hope that's all your problem is.

Good luck yourself.

 

[rdye]

re: detonation

That was my initial thought but it is running great and I am running 91 octane, no ethanol. I suppose something could be throwing off the timing under load. There is no pinging. Computer controls timing so I am not sure what I can do about that other than restting the computer. Plugs, wires, distributor, all new within the last 12 months.
Whatever the rattle is, it is not affecting performance.

 

[Atticus]

Not to beat a dead horse, but did you take the upper shields off, or just hit them with the mallet to test for "looseness"? I think I'm going to take all the exhaust shielding off this afternoon to see if this helps. Did anyone have any problem with heat coming from the exhaust tubes after taking their upper shields off?

Thanks in advance.

 

[rdye]

I didn't take them off but I may still do that. I beat on them cold and hot. They are solid. Some people take them off. They look useless to me so I would go ahead and take them off if you want to.
I read a lot of threads searching "rattle" and a lot of guys said they removed them because they were in poor shape or half rusted off and rattling. Nobody mentioned any problems resulting from the removal.

 

[rdye]

UPDATE:

I drove the LC to my mechanic and reproduced the sound by power braking. My mechanic said it sounds like "ping" to him. He asked me about the base idle and I talked to him about decarbonization. They don’t have a decarbonizer but he bet I would notice a significant difference in performance and gas mileage if I had that done. He also suggested not messing with the base idle to get rid of the ping until after trying the de-carbon since I like the performance now. Adjusting the base idle may get rid of the noise and lower performance which is what I thought and what many on the LC forum observed.
I found a mechanic that has the decarbonizer and will do the job for $130. I will post the results bad or good if and, more likely, when I get it done.

 

[Atticus]

Any update on this? My mechanic told me that he thinks that there are some "exhaust return pipes" which are leaking and need to be replaced. I don't really know what he's talking about, so when I find out the part numbers, I'll get back to the board (and most likely CDan).

 

[rdye]

I had the throttle body removed, cleaned and remounted. After that I didn't have the cold start rattle or the rattling noise and the idle is normal with no more over-revving.
I was already into the cold weather when the throttle body was cleaned and now that its warm again the rattling noise is back and I still can't find it. I do think its in the exhaust but I don't want to try any trial and error mechanics. I tried a couple of things last year and needlessly spent money.
The LC is running great so I'll just have to wait and hope its nothing serious.
Sorry I am not much help.

 

[Atticus]

I had the throttle body removed, cleaned and remounted. After that I didn't have the cold start rattle or the rattling noise and the idle is normal with no more over-revving.
I was already into the cold weather when the throttle body was cleaned and now that its warm again the rattling noise is back and I still can't find it. I do think its in the exhaust but I don't want to try any trial and error mechanics. I tried a couple of things last year and needlessly spent money.
The LC is running great so I'll just have to wait and hope its nothing serious.
Sorry I am not much help.

Well, it sounds like we are suffering from the same condition. If this fixes it, I'll post back. If not, keep me updated if it makes you crazy enough to tear into the exhaust (I'm clearly past that point now. Damn rattle agitates me).

 

[CJF]

I had the throttle body removed, cleaned and remounted. After that I didn't have the cold start rattle or the rattling noise and the idle is normal with no more over-revving.
I was already into the cold weather when the throttle body was cleaned and now that its warm again the rattling noise is back and I still can't find it. I do think its in the exhaust but I don't want to try any trial and error mechanics. I tried a couple of things last year and needlessly spent money.
The LC is running great so I'll just have to wait and hope its nothing serious.
Sorry I am not much help.

Doesn't sound like you've eliminated pinging as a suspect. If that's the case, it is potentially very serious.

A few 3FE'ers have recently had very good luck controlling pinging without backing off the timing by richening up the fuel mixture via adjusting the Air Flow Meter.

Curtis

 

[Tentsontop]

Mine rattle wasn't under the hood, but was shield related. Try looking at all the clamps on your shields. I had one other 93 that rattled. It didn't make any noises when I checked it out much like you have, but after removing the clamps I found rust issues that were allowing the shields to flex and rattle at high rpm. After replacing them - no rattle.