LS400FAN

Any ideas where the clicking noise is coming from? It only happens when I accelerate from a dead stop until it gets up to 30-40 mph, when at idle the engine is real smooth, even at 20 - 30 rpms without the clicking sound which rules out the valves. My guess is the tranny, could the mounts be making this sound under eng. load? Has anyone ever had a clicking sound coming from "inside" the tranny? Btw, not much zip on takeoff either. Any help on this is much appreciated. Thanks.

dicer

Yes (edit) I have something like that when first starting it up, kinda sounds like loose flex plate to torque converter bolts, I have not had time to investigate it. It doesn't make the noise after warm though so likely not loose bolts.

YoshiMan

Are you using premium fuel? If not, could be engine knocking

RA40

iTrader: (6)

From inside the car when an engine "clicks" I also suspect knocking. What gas is being used? Last tune-up?

LS400FAN

Thanks, let me know if you find out anything, and I'll do the same if I find something.

LS400FAN

Absolutely, I never use anything but premium. Like I said, there is no noise when the eng is in park or neutral, only when it's in gear and driving off.

LS400FAN

Thanks for your reply, but the eng. runs smooth as silk while in park or neutral, even when I kick up the rpms. The clicking noise is only after put it in gear and take off, but only til it reaches 2nd or 3rd gear then it goes away. I know it could be almost anything, but it doesn't seem to affect the eng perf.

timmy0tool

iTrader: (7)

what year is your car? if not newer than 97 i suspect your EGR pipe is leaking causing a "clicking" noise. i have mine leaking and gives a similar sound that can be mistaken for something else.

RA40

iTrader: (6)

timmy0tool has a good thought. Engines ping when under load and typically in the 1-2 shift when it is trying to deliver HP-torque. Using lower octane rated gas where the spec is for higher ratings also introduces spark timing issues that may lead to this. The common suggestion is to run a fuel system cleaner and the specified rated gas.

LS400FAN

timmy thanks for the tip, were you able to determine the ticking during take off or while idling or both? Again, there is no ticking while I'm idling, even at high rpms.

LS400FAN

Thanks RA, I've always used the highest octane gas, and I regularly use Sea Foam as a cleaner, maybe I'm using too much. Either way, wouldn't that throw a code? It idles at 1500 rpms continuously, even after warm-up, and then gradually comes down after about 15 mins. of driving., could that be connected? I'm starting to think the ECU could be the source, especially after following Cowboy's thread about leaking capacitors in the ECU. What's your take? Tia.

timmy0tool

iTrader: (7)

well 1500 at idle is high. sounds like the idle control valve is stuck then gets loose at temperature. might be worth cleaning.

my leak or "ticking" goes with RPM regardless of load since it's an exhaust leak. it's more prominent under load but it's there if i rev at idle too. it was just another theory to check.

if the car is a 1st gen, an ECU rework is always a good idea regardless of condition. you said there is hardly any zip at takeoff too.

RA40

iTrader: (6)

That ECU thread and symptoms can be pretty head scratching. If yours is a '97 or older, checking the ripple results would be next on the inspect list. The consensus is to get in and replace the capacitors anyhow because they have a known life expectancy, sooner or later issue.

Glad you are are following manufacturer spec on gas. Some mange on lower grades so that may or may not be a factor with certain running situations arise.

randal

A thought on experimenting with this, LS400FAN, but if it "clicks" during acceleration briefly going forward, would it do the same thing going backwards? Now, bear with me a moment. You said that you suspected the tranny or mounts.... so if you found an empty space where you could safely and briskly accelerate in reverse(for a short distance), the engine would still have an equivalent load and should ping briefly if octane(or timing) is the issue. But if the issue lies in the tranny or other connecting drivetrain, it may be a different "click" or no click at all. Just wondering.

LS400FAN

Thanks for the info tim, I do plan on changing my ecu next Spring, but I'm convinced the problem is not in the engine, at least while it's in neutral, based on that I've ruled out exhaust leaks and eng misfires (unless it's ECU related) when the tranny is engaged. Right now it's really not a problem and may have been there for quite some time and I never noticed. I know there was a recall on my ECU for the 2nd gen 1995 models, which I doubt was replaced. I'm not too worried for now, the good news is if the problem gets worst it will be easier for me to diagnose, but that doesn't mean I won't continue scratching my head about it.