So I own a n automatic 94 2+2, and recently theres been this constant tapping sound coming from it. I wouldn't say its coming from the engine itself, but rather somewhere behind it or under it. The tapping also seems to correspond with the rpms, since it'll get faster if I rev it, and then go back down as the rpms go down. A coworker of mine compared it to something he experiences with his truck, the "Hemi tick", which is caused by fluids that aren't warm yet running through the engine. It used to be constant as the car would run and drive, now it'll be super prominent when it starts up, and slowly go away as the car settles. However, this sound has been linked to the engine going into limp mode about 3 times now, whether it's not going out of first gear, or topping out at 50 mph with poor throttle response/power loss. (ie. not reacting when pushing the throttle past the sweet spot, topping out at 50 and not going above 2000 rpm, etc.)

So I guess in short, does anyone know what this tapping noise could be? is there a simple cause for it than can be fixed? Has anyone experienced this or something similar?

some theories I have are bad fuel injectors, which I believe to be the case. However things like misfires, cracked pistons, or even rod knock, are all on the table.

Welcome to the club Maurice. I would try an oil change and some lifter treatment to start with.

Hi and welcome Maurice!

My question - does it happen when you are driving, or when the car is stationery, or both?

If it happens when the car is stationery - IE you can hear the noise when you open the bonnet and rev the engine - I'd start with what Gary says above. New oil and filter and perhaps some hydraulic lifter treatment as you could have a sticky lifter.

If it's all good whilst idling, but you get the sound only when driving, from what you've said about limp-mode (or safety boost) you could have engine knock; AKA pinking under load. Your ignition timing could be out, your fuel mixture too weak or you're using poor quality (low octain) fuel.

Find someone with the proper diagnostics and get a full check done to determine the cause. If it's a light tapping under load - but not when stationery, it doesn't sound like it's mechanical.

How is your oil pressure? The hydraulic lifters can make a right racket if they aren’t behaving. You’ve also got the variable valve timing solenoids, they’re right down the back. When was the last time it had a service? Do you have a good service history?

The zed engine management is old school and does not have a limp home facility like modern engine management systems.

However the gearbox does and usually will stay in 3rd gear once it goes onto that mode.

The ticking noise sounds like lifters tick, sounds like half speed to engine revs, could be the wrong oil try a change 10w 40 semi synthetic( not full) and after if required try lifter adaptive.. ir actually can help.