Tapping nose when pressing the gas

[Ultimatedsm]

Hey guys I have a 90 motor in a 1995. Anyway everytime I rev my car past idle my car makes a loud tapping noise. The tapping goes away at idle. Anyway I popped my hood and reved it again to see where it is coming from. First I checked the timing belt area and no it wasn't coming from there. I check right over the valve cover, its a different kind if light tapping noise. However when I put my ear right over the injector/intake manifold area I can hear it get louder when I rev it. I also noticed on my boost gauge once in the while the tapping gets really loud than goes to a lighter tapping nose, when this happens my vacuum goes from 18 HG to like 14 HG than goes back to 18 HG again. So right now I have no clue why its doing this, could it be a leaky injector? I don't know, any idea guys?

450cc injectors (Original 10 years old)
walbro 255
3 inch exhaust
HKS megaflow intake
DSMLINK

 

[DSMcrazy3]

BOOST LEAK or MAF You know I'm playing...Anyways I would suggest getting a wooden pole and putting it where ever you think the noise is coming from, and the other end to your ear. I think now actual Stethescopes are made for cars that do the same thing, just much better.

Sorry I don't know what it is, but that will help narrow things down.

 

[Ultimatedsm]

BOOST LEAK OR MAF!!! Well, it could be either two things, my lifters are just ### and love making that noise, or my injectors need cleaning or something. Weird when the tapping gets loud my boost gauge vacuum drops by a 4-5HG than goes back to normal again.

 

[Ultimatedsm]

I did a few extra tests today to see what the hell is going on. I notice a slight misfire at idle when the car warms up. I triple checked where the noise was coming from and I know for sure its not the lifters. When I rev around 1500 RPM you can really hear the noise around the fuel injector area. I went in my car and reved it at 2000 RPM the vacuum is around 17 HG and when the tapping noise comes in it drops to 12 HG. The tapping noise is only under load.

1. Misfire at idle.
2. Tapping noise coming from injector area underload.
3. Vacuum drops around 4-5 HG when tapping nose happens.
4. Doesn't happen at idle.

I have a DSMLINK log and noticed the BOOSTES feature only measured 12 psi and my car is set for 15 psi. I get 15 psi on the autometer gauge and the ecu registers 12-13 psi. Hmmm....so I am leaking 2 psi somewhere.

Could this be the intake manifold gasket leaking? ANY IDEAS WILL HELP!!!!!!! So far I haven't got any help, come on guys you guys are the best at finding problems out.

 

[Ultimatedsm]

Sooooo any ideas guys?

 

[92redman]

How did you rule out the lifters? If the lifters are getting stuck, they could be holding the valves partially open thus causing your vacuum drop at the same time the tapping gets louder.

 

[Ultimatedsm]

That sounds logical. I ruled out the lifters because I put my ear all around the valve cover and the ticking was much louder at the intake manifold fuel injector area. The car kind of misses at idle as well. A lifter being stuck open? I never heard of that one.

 

[Defiant]

Rear balance shaft bearing.

 

[Ultimatedsm]

Rear balance shaft bearing? What are the sympthoms of that and how do I replace that?

 

[Ultimatedsm]

Anyway before I assume its the balance shaft bearing I am going to pull the pan. If its good, than its something else. I don't hear a ticking in the timing belt cover area or crank pulley area. Its right in the fuel injector area or beginning of the intake manifold runners area. When this ticking happens WHEN the car warms up (Ticking doesn't happen when its cold or at idle) the vacuum drops by 4-5 HG, would a balance shaft bearing cause that as well?

 

[tech27]

hey guy sounds to me like you may have a faulty injector or injector oring a good way to test is to take brake washh and spray on the injector(s) you suspect are leaking if you have a leak there the motor should rev rpms slightly hope this was a help to you

 

[Ultimatedsm]

Apparently a shop that repaired a few things on my car told me that a 0-ring was leaking in the injector area. Well I should just replace all the o-rings and see what happens. I will drop the pan tuesday and check for metal shavings if its the balance shaft bearing (Still doesn't make sense why that would drop vacuum and only happen when the engine is in its operating temps) than replace my o-rings.

 

[GSXTuner]

i was having a similar problem a couple days ago, and the symptoms seem similar to yours.. i at first thought it was coming from the injector area.. later i found out it was nothing more than my exhaust mani being loose! i just tightened it all up and the problem went away! i was amazed it was something so simple.. what threw me off was the sound really didnt make me think it was an exhaust leak until i revved it up higher.. so double check your e-mani, maybe you'll get lucky!

 

[Defiant]

Apparently a shop that repaired a few things on my car told me that a 0-ring was leaking in the injector area. Well I should just replace all the o-rings and see what happens. I will drop the pan tuesday and check for metal shavings if its the balance shaft bearing (Still doesn't make sense why that would drop vacuum and only happen when the engine is in its operating temps) than replace my o-rings.

Okay, now is it a tapping, a ticking or a knocking?

 

[ddavisaf]

http://www.vfaq.com/mods/ICtester.html

Your injectors tap constantly. And when at idle your vac should be at around -18vac. When you're not at idle, your readings will increase as you're closer to "positive pressure". At idle, place a piece of hose in your ear and the other length on the top of your injectors. Does that sound exactly like what you're hearing?

I wouldn't suspect a balance shaft bearing yet.