Pop.... sound?

[Woodyb1]

Okay,

this is the deal, I have taken very good care of my 94MTX, both 60K & 120K. Replaced anything else that needed it too. However I have noticed since I had the car ( 60K) that there was a slight pop (doesn't sound like a tick you get from mechanical lifters) coming from between the heads, closer to the front head)

I am 99.9% sure it is not coming from the valve train. The valve shims were all within or adjusted to specs. The car has 123K. Runs great, no problems at all.

What do you think is making the sound? Could it be a noisy injector?

 

[sdpatt]

I respect the care that you have provided for your car. Without being able to point my ears or stethescope toward the source of the noise, I will say that a pop from the front of the engine (passenger side) near the top of the timing belt cover could be a very loose timing belt. A pop from the rear of the engine at the bulge in either of the valve covers could be a very loose timing chain.

If the sound is emanating from the center area of the engine, it could possibly be, I am sorry to say this, a loose piston wrist pin or connecting rod bearing. The rod bearing service is a non-financially-stressed repair ( see my story here ), but the wrist pin could be.

Under what engine conditions is the sound produced? Steady idle? Closing throttle? Opening throttle?

 

[Woodyb1]

OOPS....I meant to say...when you are standing in front of the car looking down at the engine the sound comes from underneath the intake runners about the middle of the engine not from the cam chains/sprockets or the timing belt area.

The pop increases with RPM though not in intensity (never gets louder)...I will try a stethescope though to see if I can pinpoint it. I did put my ear as close to the sound as possible and it does sound like it is coming from the area around one of the injectors.

The sound is more noticable at idle, I'll check the sound at full throttle to see if it is there. It really is not very loud, and certainly hasn't affected my performance.

<small>[ February 19, 2004, 01:34 PM: Message edited by: Woodyb1 ]</small>

 

[AutoSHO]

Sounds like an incorrectly shimmed valve.

 

[Woodyb1]

I may check that this weekend, but I was sure that everything spec'd out. I had the sound before I did the first 60K, I want it right. So maybe I will pop off the cover this weekend and check. The engine sounds great otherwise....the pop has never gotten louder....how about this, valve spring?

<small>[ February 19, 2004, 01:43 PM: Message edited by: Woodyb1 ]</small>

 

[AutoSHO]

Did you replace all the intake gaskets as well?

That is a very unusual place for a noise to come from. I would do as Scott said and try to pinpoint the noise.

I've never had an injector get noisier than the rest, although I suppose it is possible.

 

[Woodyb1]

Yes, I replaced all of the gaskets, I just got back from NAPA. I bought a stethoscope and the sound was coming from the fuel rail, no noise from valvetrain.

I have isolated the noise to the middle cylinder on the piston bank facing the front of the car. You can hear the pop/pulse when the injector is opening and closing through the stethoscope and you can also feel it pulse (vibration) through the stethoscope probe. So what is the solution, I guess I could replace the injector? I tried some cleaner, I'll run half a tank of gas through it...4.95 cheap even if it doesn't work. I may end up replacing the injector though.