Engine rattle at cold startup

[nlt99]

Hi!
I have a 2003 FWD CXL with the 3.4L engine and about 131,000 miles on it. The first startup of the day, I hear a very brief, sharp rattle or rapping sound from the engine area. It only lasts about a second or so then stops pretty abruptly. If I pull fuse-11 for the fuel injectors and crank the engine for 10 seconds or so to build oil pressure, then re-insert the fuse, the noise doesn't occur.

In previous cars that had cold lifter noise, it seems the noise would quiet down a little more gradually, and last a little bit longer, but I am not that familiar with the 3.4 engine yet. I thought possibly rod bearings, but again, in the past it seemed if I had rod bearing problems I would also hear it when I "floated" the engine.... rev it up and just when lifting the accelerator I would hear the noise again. I haven't noticed that with this engine.

I thought I had read somewhere that something in the tranny could produce cold-start noise but I can't find that info again anywhere so I may be mistaken about that. Has anyone heard of that?

If it were something really off-the-wall like timing chain rattling against the cover (if that's even possible in this engine), it doesn't seem that building oil pressure before starting would affect it.

One other detail that I am trying to verify right now is that if I just start the engine and shut it off without allowing it to warm up, then on the first start the following day the noise MAY not occur. I need to do a little more research to see if that's consistent or not. IF this proves to be consistent, then it would seem like the oil is staying put instead of draining out unless the engine is totally warmed up or driven for a while...... not sure what that might point to though... maybe someone else does have an idea?

I am using an AC oil filter since I read that some others may not have an anti-drainback valve, but that hasn't seemed to affect this problem.

The only other noise I notice from the engine after starting is a very faint intermittent ticking sound.... individual tick, not a series of them. It reminds me of the timing gear tick I used to get in my Porsche engine years ago, but I think this engine uses a timing chain, not gears... anyone verify that?


Thanks for your thoughts and input! Nick

[Mr. Brownstone]

The rattle noise you are hearing is the lifters. The ticking after it is running is the fuel injectors working. What engine oil are you using? My want to run a heavier oil. Also, there are oil additive available at auto parts stores that take care of lifter noise. Might want to look into trying that out too.
If you haven't replaced the intake gaskets yet, consider a new set of lifters when that time comes.

[nlt99]

Thanks very much for your reply... I appreciate it!

Is there any good way to verify that the rattle is the lifters for sure? The rattle is pretty sharp and very brief... maybe 5-10 good raps, then gone. I have been thinking of replacing the lifters and the upper/lower intake gaskets at the same time since I also have that intermittent misfire on the even-bank cylinders which I'm thinking could be due to a small amount of coolant leakage into the cylinders.

The ticking after the rattle disappears does not occur at an even enough timing for me to think of fuel injectors, but I will listen at the injectors more closely to see. It is also more of a mechanical, slightly heavier tick than I would expect lifters to make, and intermittent timing. I'll let you know if I can determine more on that.

I am running Castrol GTX 5w-30 at the factory recommendation. BTW, I live near Phoenix so was wondering if 10w-30 might be a better choice. Factory spec's say it's OK above about 0 degrees, which we never see here of course.

Do you have any specific recommendations regarding the additives you mentioned for lifter noise?? The only additive I've had luck with was Engine Restorer, but that was for smoking and oil consumption... which it cured quite well.

Thanks again! Nick

[Mr. Brownstone]

I've never used an additive for lifters. I only read about what others on the web have used. If your intake gaskets are leaking, it would probably be wise to just replace the lifters while its apart. 10w30 or 10w40 would be fine. I run 20w50 in all my cars though, 150,000 miles + on them.
As for the noise, brief rattle that quickly goes away is indeed a lifter tick. If it were piston slap, it would take at least 10 minutes for it to subside, and most time not go away at all. It would be alot louder too.