Cleaned Throttle Body, now strange knocking sound from engine

A

aquilles10

Member
Location
Los Angeles
Car
2018 QX60
My 04 FX35 was having problems starting when cold due to a dirty throttle body. So I followed the instruction on this board and the cold start problem has gone away. However, I've had new problems emerge since the throttle body cleaning. For one the annoying Service Engine light is always on. Then the idle is high so I've tried to do the pedal dance to reset the check engine light and adjust the idle. I successfully turn off the service light, but the check engine light keeps coming back on and the idle remains high (around 1.2k RPMS at start up and 750 at warm idle).

But now something more annoying has developed. There is a strange sound coming from the front of the engine. It sounds almost diesel like (ta-ta-ta-ta-ta). It comes and goes and I can hear it on the freeway when I am just cruising at a steady speed. As soon as I step on the brake gradually, the sound immediately goes away. Then it eventually comes back. It's almost light a light mechanical knocking sound and I think it's coming from the pulley area. What could this be? And could it be related to the Service Engine Light?
 
Take your car to the nearest Pepboys and have the codes pulled for free. Autozone doesn't do this anymore. Report to us the codes you find.

I believe 750 rpm idle is normal. I'll have to go out and check on that one.
 
650-800 RPM idle is pretty normal after a warm up. Were you careful when cleaning the throttle bodies? Did you use a dedicated throttle body cleaner and a soft lint free cloth when performing it? The throttle bodies are soooo sensitive, so that's why it's always a good idea to take safe precautions when cleaning or messing with them.

By the way when you removed the throttle body did you disconnect the throttle position sensor? Usually if you leave them connected it doesn't reset the computer so you dont need to do a throttle position and idle relearn.
 
Last edited:
Yes. I was as careful as I could be when I cleaned the TB. I used an old, clean t-shirt and a dedicated carburetor/throttle body cleaner and I made sure that the throttle body didn't slam shut when I was cleaning it.

Here is a photo of the RPMs once the engine is warm. It's a tick under 1k RPM.

 
Last edited:
Okay, so I think I figured out what may be going on thanks to my local mechanic. I went to his shop and although very busy, he plugged in his ODB-II scanner to my FX. Two error codes came up. One was for the high idle which I already knew about. The second one was for a "valve cam timing error". This one is a little more embarrassing. My mechanic asked me when the last time I changed the oil was and I said a few months ago. It turns out that dirty oil can cause the cams to stick and cause the check engine light to come on. He said to change the oil and that the sound and the CEL may go away.

How freakin' embarrassing! It just must have slipped my mind to get the oil changed sooner. Hopefully, my mechanic is right.
 
Yes, it started shortly after. I don't know if they're related or not, but it started after the TB cleaning. I can't remember that there was that sound before the TB cleaning but it may have been there albeit a lot less noticeable.
 
You know, the knocking noise can be an indication of low oil....

Knocking probably has nothing to do with the throttle body. The knocking probably coincidentally came after throttle body cleaning. I suspect you starved your engine of oil and there is a high likely chance that you may have toasted your engine.
 
Last edited:
aquilles10 said:
This knocking IS NOT subtle. It sounds like an old diesel Mercedes only not as loud.
Click to expand...

Man, I'd get that checked out ASAP.

No CEL's or smoke? Is it remotely possible that something fell into the Plenum while the TB was removed? Did you mess with the plugs at all while you were there?

Sent from my DROID RAZR
 
I changed the oil and did the pedal dance to reset the ecu. The knocking sound is gone and the cel light is off and hasn't come back on. There was never any smoke. The FX sounds normal once again. I think I'll check the engine oil much more frequently here on out.
 
Thanks. A few days later and the CEL is still off. The RPMs at start up are still a little high so I'll have to do the pedal dance to reset the air volume idle.
 
You must log in or register to reply here.
Back
Top