Raymr

Hi, I posted this question in General Rotary Tech but thought I would try here as well. I just installed a rebuilt in my 88 N/A and there is a steady tapping noise that sounds similar to a bad lifter in a lesser engine .

I swapped injectors and made sure all was snug under the DC, but that didn't help. It's there at all speeds. If I rev the engine and cut the ignition, it keeps making the noise until everything stops turning. I think this rules out electrical.

I'm having real trouble pinpointing the source since the whole motor acts as an echo chamber. I've ruled out the ACV by using a "no-holes" gasket temporarily. I can hear the tapping both above and under the engine. It seems loudest when I use my stethescope hose on the round tin-can thing on the ACV, but that may just be echoing from somewhere else (somewhere in the intake tract?). What could this be??

Rxmfn7

iTrader: (4)

Does the tapping get faster as you rev the engine?? Check all your accesory pullies, make sure your belts arent hitting anything. I really cant think of anything that would make that kind of sound other that something bouncing around in the rotor housing.

Raymr

Yes, it gets faster with the revs. The accessory belts are in good shape, or new. I think something in the rotor housing would have been kicked out by now. If it were inside the rotor itself, wouldn't higher speed and centrifugal force pin the object against the sides, making the sound stop, or at least change? ...Help.

ALTurbo2

I wouldn't call it a tap, but you might want to check the aux. port actuator rods. The little piece on the end can make an annoying click sound when it's loose.
just a guess.

S2-13BT

I recently had a tapping noise from my engine. It turned out the rear trailing plug was loose, and it would move in & out just enough to make the noise. It drove me crazy for a week, until eventually I noticed the plug moving (very slightly). Tightened it up and away I went.

NRA T2

possible A seals?

CrackHeadMel

iTrader: (2)

I had a taping noice, turned out my fan was hitting the shoud, seemese obvious now but when i was tryig to find that damn noise..

Raymr

I'll try running it briefly, with some of the accessory belts removed, to rule those things out.

jacobcartmill

iTrader: (6)

must be those damn sticky lifters

Spraintz

iTrader: (1)

I have never had a rebuilt engine.....yet but I wonder if there could be some excess noise during break-in.

Just a thought.

selanne8

make sure your spark plug wires are correct, could be slight detonation. just a guess...

john

Raymr

Thanks for the ideas so far. I'm at wits end. I took off the A/C and P/S belts. No change. Spark plugs are tight, retraced the wires, even though they are marked with a white dot and band. I'll try to make a recording and post it on here.

Rxmfn7

iTrader: (4)

Is it maybe a transmission noise?? A really worn throwout bearing may make a grinding or tapping noise. Just throwing out ideas....

Raymr

Clutch, pilot and throwout bearing are new.

darkwaveboi

mine makes a steady squeeking sound from the tranny area during low rpms, gets faster as car speeds up.

what could it be...hmm..

Raymr

My tranny's fine.... I'm concentrating on the engine now.

SureShot

I'd test the plug wires, maybe swap the set with a friend's set..

Rotary Racer

If that tap increases when the motor is increasing in RPM's then you have a simple exhaust leak (don’t stress). Where I can't tell you but I would check between the block to the manifold and manifold to down pipe. Your should be able to feel it easy at about 1.5k or so (don’t rev it up to much it’s a rebuilt) And make sure your O2 sensor is in tight. Have fun

Raymr

The pipe and manifold connections are solid and tight. I took everything off down to the lower intake and reassembled. No change. On closer inspection I saw cracks in the EGR diaphragm, and it doesn't hold a vaccuum. Could a bad EGR cause this kind of noise?

SupSai7

iTrader: (8)

Mine taps too, can't figure out what the hell it is though. Mabe when I quit being lazy I'll work on it. It's not effecting anything just annoying.

Rotary Racer

Yes if the EGR is cracked or leaking it will make that tapping noise.

jmseven

Chk your engine mounts.

SonicRaT

iTrader: (6)

Mine makes a rather annoying tap noise, but that's just the exhaust leaking out freely from the downpipe & manifold (whoops) Goes away once I go past 3,500rpm tho

Raymr

OK, where can I find a good EGR valve, besides the dealer? My local parts store doesn't carry them.

RX-7Impreza

block that piece off well unless you have admissions..... I LOVE THE SOUTH

if that doesnt fix it i would try retarding your timing a degree, or putting in 93 octane. just for ***** and giggles