Noisy Fuel Injectors '89 S2? (long post)

[gheedunk]

After replacing both motor mounts I now can hear a whole host more noises coming from the engine compartment. It is very apparent at idle (is prominent with the windows down and can also hear from under the car), but is drowned out by regular engine noise during driving.

I've been searching this forum and others for a source of this noise, but like WebMD.... it could be everything.

I believe it is the fuel injectors, as it follows RPM, is at greatest intensity at the top of the engine, and moving my "stethoscope" (irrigation tubing wrapped in armaflex insulation) from injector to injector produces a different volume (#3 is the loudest).

Finally, I noticed something today that may clear this up for sure. When revving the engine and releasing the throttle back to idle, there is a pause in the ticking. I surmise this is because the engine is no longer calling for fuel and the injector does not actuate. Can I conclude that because the ticking noise subsides during this period AND the engine is still rotating that it is not the following?:

a) Rod Bearings
b) Bent Valve
c) Exhaust manifold leak
d) Missing banjo bolt in the valvetrain
e) Piston slap
f) Worn valve guides
g) Broken/worn springs
h) Loose cam bolt
j) Bad lifters
k) Oil pressure relief valve
m) Cancer

And is truly noisy injectors?

Thanks in advance for your feedback.

gheedunk

[JxJ]

If it is a sharp ticking sound it is likely injectors, they are loud and louder on the S2. You can somewhat isolate it by placing a wood stick or a screw driver or mechanics stethoscope to conduct the sound from what touch to your ears. Place it on the valve cover in various places and you should hear rotation and lifter noise. If at this location there is loud clacking or banging it may be something in the valve train, likely lifters, springs or the like. If you place the stick or screwdriver on the injector piping and injectors and you here much louder ticking it is likely the injectors. I have no complete remedy but mine seems to be quieter when I run about 8oz of Marvel Mystery oil in the gas tank. I've also added Techron (12oz) at the same time, then it seems quieter, but it never goes to zero, these injectors are loud even when working right IMHO.

[v2rocket_aka944]

all 944 injectors are pretty f***in loud
but the S/S2 are extra loud because they have to work harder (higher fuel pressure)

you should have a black plastic "fuel rail cover" that has insulation foam underneath it in an effort to quiet it down...but they are still quite noticeable.

[Jfrahm]

Yes, they are quite loud. EV6 injectors can be substituted and they are somewhat quieter. I do not recommend spending money on the old style injectors, instead getting the more modern ones for a variety of reasons. Quieter, less prone to leak, better spray pattern, no pintle caps to fall off, etc.

-Joel.

[v2rocket_aka944]

I'm V2Rocket and I approve this message^^

new-style fuel injectors are quieter and make a better spray pattern than the ones the car came with.
this makes better MPG, better response, and better power.

i know it could be argued for accuracy, but i showed a +3hp increase on the dyno with multiple runs swapping to newer 4-hole injectors vs the OE "pencil" type without other changes (aside from those necessary to dial in the injectors themselves to be acceptable to the DME)

[djnolan]

The most likely or worst problem you could have on the 16V engine is hydraulic cam chain tensioner failure or worn or damaged tensioner pads. This would cause the chain to damage the head and possibly be the noise you are hearing. You would need to pull the valve cover to check the pads, etc. Tensioner replacement is prescribed at X miles. Pads somewhat earlier.

Will let the experts elaborate...

[jhowell371]

To check for rod knock set the parking brake, select 1st gear and slowly engage the clutch just enough to load the drive line against the parking brake. If it's a rod knocking the knock will diminish or stop. My S2 injectors make it sound like it's beating itself to death.

[Fast Freddy 944]

Older cars from the early 90's back have noisy injectors. Modern cars and trucks are more quiet, newer technology is less noisy. Plus that car is old, just like mine, if you get a mechanics opinion, they will tell you its worse than it really is. They got to make money off of you....