Throttle body ticking noise (ITBs)

[56]

I've been chasing an annoying ticking noise coming from the engine at idle and on overrun below around 2000rpm for a while now. It's most noticeable when the engine is up to temperature and everything else has quietened down I suppose but it's very noticeable from inside the car and really quite loud when standing near the front of the car.

It's a k series with forged pistons and Jenvey (QED) DTH ITBs and the engine runs fine but I keep expecting this noise to turn into something much worse! Anyway I've finally narrowed it down to the front cylinder on the intake side. And after more playing around I found that the noise would stop if I pushed on either the centre of the butterfly shaft (pushing towards the engine) or pushing on the end of the shaft (pushing towards the back of the car). It seems like such a small amount of movement of the shaft when I do this that I'm amazed this is causing so much noise.

I wondered if anyone else has seen/heard this and if anyone knew a solution to permanently stop the loud rattle/ticking noise? The throttle bodies were fitted new about a year ago and I think the noise has been there from the start it's just taken me this long to work it out.

[Dan R]

Now its funny you should say this as i have noticed a loud ticking noise after a longer blat when the engine is inevitably hot.  Its at regular intervals about 180 BPM and doesnt vary with speed or engine revs.  Mine is a duratec with RBTB's

[Beagler]

Injectors.

[SM25T]

Solenoids in injectors. Sounds like a sewing machine

[Beagler]

 Could hear the same on my BMW R1200RT bike.

[ScottR400D]

The clicking of injectors wouldn't stop when you pushed on the butterfly spindle. 

[Dan R]

A sewing machine, thats exactly it...... but only when its hot?? and doesnt change with engine speed?? (That i can remember anyway)

[56]

For a while I thought it was the injectors but using a screwdriver to my ear on them I couldn't pick up the same noise. Also I swapped the injectors around and the noise still seems to be coming from the front cylinder. I'll do some more investigating today.

[revilla]

Is it absolutely regular, or is it an erratic tick .... tick tick ... tick kind of thing? I recently looked at a K Series that was doing this. Sneezing, they call it. There was a leak on the inlet manifold gasket and with the high vacuum and low air flow at idle, this lead to air being drawn in and a very lean mixture on the affected cylinders. Very lean mixtures burn very slowly, so there were still pockets of burning gas as the inlet valve opened, igniting the incoming charge behind the throttle butterflies. In a dimly lit garage you could actually see orange flashes around the edge of the butterfly in time with the ticks. Poking around the butterfly would either make it worse (affecting air flow) or better (stopping it rattling!). There's a video of it here:

, you can just see the flashing. That doesn't capture the sound well as the phone microphone was stuffed right up the inlet trumpet and drowned out by the inlet sound, in reality it did just sound like a light intermittent ticking, like something mechanical loose. When we took the TBs off the gasket was clearly shot and a new gasket fixed the issue.

 

[56]

That's interesting Revilla. I did wonder if it could be some sort of combustion still happening when the intake valve opened. But in my case it's very regular and I couldn't see any flashes around the butterfly.

I took a quick video showing what happens when I press on the end of the butterfly shaft

[revilla]

Yes that does sound like a mechanical vibration of the butterfly valve with the pressure variation. I don't think it's the same as I was seeing. When you hold the spindle and it goes quiet, the residual mechanical chattering you can hear in the video is the (perfectly normal) sound of the fuel injectors, so this is something different. I'm afraid I haven't payed with Jenveys enough to know how normal or otherwise this is. Sounds a bit like the spindle bearings may be worn and slack allowing the spindle and butterfly to move a bit, which doesn't sound ideal but again, I don't know if it's normal or not.

[56]

Thanks, that's what I'm thinking too. It's very good to know it's not something inside the engine going wrong but still a bit annoying that I can't easily stop it. If it's not normal, I wonder if the throttle bodies are serviceable.

[7 wonders of the world]

Jenvey will service TB's no problem, they will sell spares but only if you can convince them you know your way around the products, I got new spindle bushes and seals etc for mine and rebuilt them after a very similar situation.

[Dan R]

Well i can confirm that the noise i hear is nothing like these.  Its a much finer sounding ticking noise that is absolutely regular at all speeds, although you can only hear it at lower speeds as i am assuming the noise from exhaust, wind, intake etc drowns it out 

[56]

That's really good to know, thanks. Out of interest what sort of mileage did yours do before you rebuilt them?

[56]

Just to update this..

I must say I had fantastic service from QED and Jenvey. I sent the throttle bodies back to Jenvey and within a week they had sent back what appears to be a brand new pair. I have fitted them and the noise seems to be slightly reduced but still present. By lowering the idle speed I could get rid of the noise completely at idle but it's still present at very light throttle just above 1000rpm so not a complete solution. I think I have to put it down to a characteristic of the engine unless I can find another solution.

[21jigsaw]

Just a thought i had a similar noise on my 1800k running throttle bodies and dry sump  it was due to crankcase depression. So does removal of the oil filler cap have any effect on the noise.