I Have A Tick.....

[Tim Kay]

And it's driving me bonkers! Best described it sounds uniquely similar to a loud spark plug arc, what you hear when holding a spark plug to ground while the motor turns over.

It only occurs at low throttle position. Either with an abrupt throttle blip while idling or while cruising then stabbing the throttle creating a significant load. Generally I will only hear one click on occasion two and I can repeat it on demand, hot or cold, any gear. It won't occur if throttle position is more than 20-25%. Again, it seems to be throttle position and load sensitive. The sound comes from only one area which is on the passenger side of the motor.

Initially I thought it was a valve spring or loose rocker arm and then explored the possibility of it being exhaust escaping through an intake valve and up into the throttle body. I've had the heads off and checked springs, valves and rocker arm assembly and everything is good there.

The dizzy cap and rotor are new. Next thing I'm going to try is replacing all the spark spark plug wires.

Any ideas?

Tm

 

[Darrin]

I was going to suggest the wires myself. Relatively inexpensive.

 

[Frank Catt]

Tim, are you on Webbers or Holley ?

 

[René]

if it is only one or 2 clicks then it could be that say your gas-cable or movable parts that make the movement in that line, come across/scrubs some other wire/cable and makes contact or so?

 

[Glenn B.]

If you don't have an automotive stethoscope, I can highly recommend using one. Have someone in the car pressing the accelerator while you trace the source of the noise with one of these. It has saved me hours of frustration.

[ame=http://www.amazon.com/Lisle-52750-Stethoscope-Kit/dp/B0015DLMOO]Amazon.com: Lisle 52750 Stethoscope Kit: Automotive[/ame]

 

[Ian Anderson]

Start it at night and with rear clip open.

Watch around distributor for the spark as you blip throttle.

Reroute that spark plug wire and job done no$$$$$

Ian

 

[Frank Catt]

From Tims description, I am thinking transitional vacuum leak.

 

[Tim Kay]

Tim, are you on Webbers or Holley ?

TWM FI throttle bodies

if it is only one or 2 clicks then it could be that say your gas-cable or movable parts that make the movement in that line, come across/scrubs some other wire/cable and makes contact or so?

Already checked for rubbing or chafeing parts.

If you don't have an automotive stethoscope, I can highly recommend using one. Have someone in the car pressing the accelerator while you trace the source of the noise with one of these. It has saved me hours of frustration.

Good suggestion

Start it at night and with rear clip open.

Watch around distributor for the spark as you blip throttle.

Reroute that spark plug wire and job done no$$$$$

Ian

This has crossed my mind. Is this from experience Ian?

From Tims description, I am thinking transitional vacuum leak.

Explain further Frank. I'm not sure what this means. Thanks.

 

[mark b.]

exhaust manifold leak will sometimes tick like that.

 

[Tim Kay]

exhaust manifold leak will sometimes tick like that.

This had not crossed my mind, I'll check this.

 

[Dave P]

Tim:

Ian's Answer has happened to me years ago. But I would also check for a cracked header

 

[Tim Kay]

If the header was cracked or there was an exhaust manifold leak wouldn't the click be more often throughout the RPM range not just one tick at the initial throttle input?

I just bundled and tied back all the plug wires, on the passenger side, away from any steel that they could possibly ground to and at one unavoidable area I insulated rubber around the steel to further avoid grounding and no change.

 

[Jon Briggs]

Could it be a lifter?

 

[Dave P]

It is hard to say on a crack. Should be easy to spot usually a black trace of carbon. I have had plugs leak around porcelain too it mad a odd sound

 

[Paul W]

Cracked/Leaky header pipes sound like a loose tappet.

 

[Ian Anderson]

Hi Tim

Yes on my Rover engined car!
I put it down to cross arcing as vacuum moved the advance just enough for the spark to jump before the revs picked up.

I since learned that there is a very specific routing for the leads on a Rover distributor as it is a known fault.

Firing orderRover equals Ford so I would suspect the same could happen

Ian

 

[Tim Kay]

Could it be a lifter?

I have not removed them and physically tested each lifter but when the heads were off I was able to inspect the cam lobes and there was no adverse wear. With that I assumed my hydraulic lifters were fine. They're also holding normal presure in the valve train.

Hi Tim

Yes on my Rover engined car!
I put it down to cross arcing as vacuum moved the advance just enough for the spark to jump before the revs picked up.

I since learned that there is a very specific routing for the leads on a Rover distributor as it is a known fault.

Ian

Was the spark jumping at the rotor cap, outside, inside or down stream from the cap? When you say "routing" are you refering to the way the wires lay coming off the top of the cap (mine do overlap on a couple due to limited space)? Or are you simply refering to the route the wires take to get to the plug?

FWIW, I'm using MSD 8.5 silicone wires, MSD coil along with an MSD box.

The next thing I'm going to do is put it in a dark shop and duplicate the issue to see if any "light" can be shed. That's gonna have to wait until next week.


Great suggestion, all. Thanks and Happy New Years guys.

 

[Paul W]

Not sure if your heads have the emissions take offs on them like the edel-brock performers do - might be worth checking if there are the threaded plugs in the ends of the heads and they are tight.

 

[Ian Anderson]

See Land Rover Tech Tips, Maintenance & Troubleshooting Information For All Rover Vehicles

Note how number 2 runs across distributor not around the outside

That is where my spark was jumping

Ian

 

[René]

experiences in the dark
lol, but indeed in the early days when spark plug cabs were not so good or damaged I also checked in the dark with running engine and blip the throttle a bit, you then can see it good if there is a short circuit.

also maybe you are richer then you know...could be a lost coin or something like that...
or does it also make that sound when you are standing still with the car and do a abrupt throttle blip...then it can't be that ofcorse.