Well, here's a little more insight into the problem. I've been having random problems with losing boost when I first crank it up. Now, my L is totally stock, so there's no what about this, or what about that... Anyway, I disconnected the boost bypass solenoid to see if that would cure the problem. Shazam!! The engine is much quieter, I have instant boost, and the brrrraaaaaatttttt noise at part throttle is gone. I drove it for two days like that, and the only other side effects are 1) The 'check engine soon' light is on, 2) The engine seems to get to operating temp faster. (I was kinda expecting that), and 3) Part throttle response is better, and improved even more as the computer 'learned'. Now, here's the punch line...I hooked it back up, and I'm back to the same old noisy truck.
The boost bypass has to be involved somehow to make that crappy noise. Has anyone else that has the noise tried this with the same result?

 

ttt???

 

Guys, a LOT of you are scaring me to the point that I feel some of you have DETONATION and you have no idea what it is and you have no idea how HORRIBLE it is to your motor ESPECIALLY when enhanced by a power adder (nitrous, s/c, or turbo).

I really hope those of you who stated, "I didn't do it until I got the chip", or "It doesn't always do it", "Sometimes it does it when it's hot", or even best, "I am running 87 octane (or 89)" realize that you're goin to BLOW your engine if you keep doing this. Piston meltage gonna happen I tell ya...BUH BYE block.

I'm sorry, but if your motor is making noises and in fact it is detonation, you should be pimpslapped for still driving it like that.

BfB

 

Naturally you have better part throttle response...you're boost comes on quicker because you have disconnected the bypass. Horrible gas mileage and emissions plus the driving of the truck will never be right no matter how much it feels like it.

Go to the dealer and have them replace the bypass. Or run some diagnostics to determine if that is the cause. Why risk it? Doesn't make any sense.

BfB

 

I was thinking, some of you may have problems w/ one of your coil packs. That's been a problem on some of the '99 and '00s in the past.

BfB

 

Yep... I've got the noise... but only when the motor is cold, it goes away completely once at normal operating temp. It's there with and without a chip.

It's definitely NOT detonation (in my case) it's a rattely noise... doesn't should anything like detonation I've heard in any of my vehicles (and I've heard it in most all my cars, including my L).

LOCOSVT: Driving around for a long time with the solenoid disconnected can damage your motor and blower... you're not venting the superheated blower air. SAL has a number of posts on this... pleading with people not to do this...

 

I have the same sound and I have just started to hear it recently. Its only at part throttle and the sound is around 3000 rpms right before the 1 to 2 upshift. I have no idea what it is, sounds like a motor or tranny noise, either way I am not happy. I thought it only did it when it was cold, but its all the time. I am thinking of taking it in and having the dealer have a listen, but I am affraid that they will say there is nothing wrong with it and give it back to me. Anyone have a good idea? Is it the motor? Or the tranny?

 

Good to see this thread still going. BfB, it's just like Dreamin said above. I feel that if it is detonation, it's only one cylinder being affected. Mine sounds almost like a rod knock, only lighter and more metallic.

Here's what I noticed just this morning - I have an extra chip on loan from JDM. I had asked him to bump the timing 2* and richen the mixture a bit. I put it in and drove to work this morning and there it was, that familiar noise, only worse than the other street program I have which has less timing.

So I still don't know. The dealer accidentely put 87 octane in my truck when I bought it new and it detonated, so I'm very familiar with the detonation sound this engine makes and this AIN'T it for sure. But additional timing makes it worse, whatever the cause. If I can save this engine from death, I want to because it runs really well. I beat a red L badly (2 lengths) from 40 - 120 mph with the same mods as me two days ago. Still scratching my head......

BTW, Lightning Tim, that's EXACTLY what I'm talking about.

Jim

 

LOCOSVT,

Which part of the solenoid did you disconnect? I disconnected the connector on the canister that plugs in sideways towards the blower and you squeeze it to unplug it. It didn't help my noise one bit. Is that the same one you did? Or did you disconnect the vacuum hose? Interesting though that yours quieted down.

Jim

 

Lightning Tim has described exactly the same noise I hear, I know it's not Gas, in England our standard gas is 95, its not a chip problem because my 99 L is stock standard, no mods.
So thats it, I still think it,s a tappet problem, I've only had my L for 2 weeks, are the tappets self adjusting ???

 

Dont forget there is a known problem with the exhaust on these trucks making some weird rattles under different vibration situations. I have had a cat and the muffler replaced due to rattles that could be heard under similar situations. if it sounds like it is coming from the tranny it may be the cats because they are next to the tranny.
Hope this helps
Doug

 

Pull your chip out and see if that fixes it. Or, put in some octane enhancer (NOS makes a good brand) and try that. You may be having detonation, then again it may not be that altogether.

BfB

 

BfB,

I guess that's as good a place to start as any. I'll buy some tomorrow and see what happens. If it goes away, then what? I have to run $8 bottle NOS plus premium gas every tankful? That will suck and be pretty expensive considering others don't have to. There has to be a reason for this. Put your thinking cap on....

Jim

 

I don't think it is the chips causing the noise. The only engine mod I have is an Airaid and no chip. It has always made the noise even when totally stock. It did it with 20 miles on it and it still does it with 17K on it.

 

Well, we want to make sure that your case is not detonation. If this is the case then you need to keep that chip out for a while until you get it reburned right.

You may not have detonation, but this will definitely help you find out.

BfB