I've been noticing this more as the weather warms a bit. When I'm cruising, everything seems fine, but when I give it more throttle, I'm getting all kinds of rattles from the engine, mostly from the driver's side, from what I can tell. The warmer the engine, the worse it gets. It sounds like someone uleashed some ball bearings in the engine and they rattle around like crazy in there.

I'm thinking about getting a 160* thermostat and a programmer to change the fan settings, but before I plunk down the money for a programmer, I'd like to get some ideas as to whether that would help me. The engine is stock, aside from the oil pump and o-ring. Exhaust is also stock all the way back.


Thanks,


-Mike

 

It sounds like you have really bad detonation. Are you running premium gas? You may need to run some top engine cleaner through there. You may even be sucking a bunch of oil into your intake through the PCV. I think the first things you should do is check your gas, run fuel system cleaner and water remover through your gas tank, and run some top engine cleaner through your engine. If it still pings, then you may have other problems. You should check your plugs too. Make sure they look good, are in the right heat range, and don't have any shiny little specs on them from detonation.

 

I have only ever run premium gas, but the engine has 90,000 miles on it and I've never really done a full internal cleaning, aside from fuel system cleaner (STP, Gumout, etc.) every 3000 miles. What's the process for running top engine cleaner through the system? Should I also look into getting my injectors cleaned?


Thanks,

-Mike

 

Search "Marbles" and you will get a ton of threads with the same problems

Well, when the search is back up.

 

I did a few searches, which is where I came up with the thermostat idea. I really don't think it's a spun bearing (read: I really HOPE it's not a spun bearing), because it doesn't do it all the time.


-Mike

 

I'd bet $50 it's detonation from what you described. 90,000 miles with no catch can on an LS1 can cause some wicked detonation. I'd run some top end cleaner through there, change the plugs, and get a catch can. AMW makes a great piece.

 

Had the same problem last year, turned out to be a bad cat converter messing up o2 readings which leaned out the mixture too much. Try to get this fixed before you do permanent damage to your internals.

I did 160 tstat too and it did not help at all. I am not saying you have the same problem, just something to be aware of. I seen a lot of posts that say "maybe lower t-stat/fan settings will help with your detonation on stock engine" but none that say "I did it and it actually helped". Food for thought.

 

I'll try to top end cleaner this weekend. If it doesn't get any better, I'll likely take it to G-Force and get them to take a look at it for me, since they're pretty close.


-Mike

 

UPDATE:

Ran some Seafoam through the top end over the weekend, changed the oil and replaced the PCV valve (it was due anyway). Rattle still happens every now and then, but not nearly as bad as before. I'm going to run some fuel system cleaner through the next tank of gas.

Just to be safe (and because I want to) I'm going to schedule a dyno tune and make sure everything is on the up-and-up. I'd like to have an experienced LS1 mechanic look at my car and make sure there's nothing else I should fix before doing any more power adding mods.


-Mike

 

Hey Mike,

So what's the update on the car? Did you take it to a tuner? A lot of us (including myself) are having similar issues and I would LOVE to hear if you found anything that solved this issue?

Thanks!

- Jeff

 

Wow, back from the dead!

Here is the latest. I pulled my spark plugs and discovered oil on the threads of #7. It also wasn't tightened down all the way, so there was a nice stain of oil running down the side of the block and off the side of the pan. I took the car in to G-Force and had them take a look at it. Compression and leakdown test were done and everything checks out, so my GUESS is the PCV system is letting too much oil into the combustion chambers and throwing off the octane. They did confirm that the rattling is detonation, so that gives me a little better idea what I'm fighting. They're advice (aside from a tune) is to start looking into a new shortblock.

I am planning to get it tuned next week when the wife is out of school (she's a teacher), since we're a two car only family. In the meantime, I'm going to order a catch can and see if I can keep some of the oil out of the system.

Mike at G-Force said we might be able to try a few things to get the detonation under control, such as colder plugs and playing with the timing during a tune. Something else that was brought up was the idea that my cats might be clogged, which would cause more problems in the A/F ratio. I was already planning to replace the entire stock exhaust with headers, catted y-pipe and catback, all at once. Expensive, but it will be one trip to the shop to get it done and I'll have it done right the first time. I realize getting the cats out of the mix will help with exhaust flow, but I want this thing to be totally street legal, wihout worrying about getting some gung ho cop writing me a ticket for illegal exhaust.

I'd eventually like to swap the engine out for more cubes, and Mike indicated an LS2 402 is probably the most cost-effective way to go. After reading up on it, I think he's right. After the new exhaust, I'll start looking at a good set of heads. That's when I'll start making decisions about whether I'm buying heads for an LS1 347 or an LS2 402, or whether I'll buy a set that will bolt on to the 347 and eventually get reported for the 402. Unless something really awful happens, I won't replace the engine until my wife is firmly established in a new vehicle (something we keep putting off because we like having no car payments).

I'll try and remember to update this thread once I get the tune done and let everyone know what the numbers are (it's almost totally stock, so don't expect huge numbers), as well as what G-Force finds out.


-Mike

 

As promised, here is another update.

I was on my way to get the car inspected when this happened. https://ls1tech.com/forums/racer-s-lounge/330972-car-ma.html

If you don't feel like reading that thread, here's the Reader's Digest version:
I ran over something.
It ate my muffler.
It ate one of my cats.
It partially ate my y-pipe.

So G-Force installed my Magnaflow catback and did a tune. I picked up about 10 peak horsepower and 7 peak ft-lbs of torque. What appears to be causing my detonation issues (and the reason Mike at G-Force wasn't able to get more out of the tune) is my cats are toast. One is clogged, and the other is physically beat up, to the point where flakes of the internal material were coming out of the tailpipe when I got home from my adventure.

So, I've ordered a set of Pacesetter LT headers and a TSP catted y-pipe. According to UPS, this should arrive at my house tomorrow, and I'm hoping to get the car back to G-Force by the end of the week, depending on both their schedule and mine.

Since G-Force did the tune, I have not heard any detonation, but Mike said it was still doing it a little. Hopefully I will see some good gains from the headers and the new cats will knock out (no pun intended) the detonation issue.


-Mike

 

dude, i had a similar experience, and it turned out to be a bolt on the donut looking piece between the cat and the y-pipe that simply rusted to SH!$. Have you checked that out yet?

 

I've got some detonation under heavy load on my TA, too. I didn't bother with the cats, but I'll give that a try and see if my pop-pop goes away.