z28onTweenkies

I hear this loud tapping sound coming from the passenger side of the motor every morning when i start it up. Once the motor gets warm, the sound goes away. It will come back here and there during the day after that, regardless of temp. It is consistent with engine rpm, and you can hear it even from outside of the car by the passenger door. It almost sounds like something to do with the exhaust, cuz you can hear it even if you stand by the back passenger wheel. Could this be valve tap, loose rocker arm, exhaust manifold issue or what? Any clues on how to diagnose it better?

z28onTweenkies

also, forgot to mention, if you watch my motor at an idle, you will see it shake and move around (missing) and also when i was cruisin yesterday on the freeway i was doing about 70 and my car was missing pretty badly down low in the rpm range. this is startin to sound like exhaust valve, back about a year ago i had problems with smog and excessive temps in the combustion chamber, uh oh....

KeithO

Mine does the same thing. Exactly. It has done it since I over-reved it last November (about 6,800 rpms).

It doesn't seem to be down on power, so I'm gonna wait till it breaks...

FstBrd6point3

pray it isn't rod knock, if you over-reved it, you could have spun a bearing, some motors can go a while with a spun bearing before andy real damage starts to get done, but it is irreverible without a rebuild. My motor only took about an hour of run time before it chewed quite literaly a 1/4 inch out of my crank and killed two of my main journal bearings.

Hg

Umm... you're scaring me here, my engine will shake and move around when it idles, it's not like a huge shake, it just kinda moves a little.... is there something wrong with my car? Or is what you're talking about a bad shake?

ZZ28ZZ

Could be an exhaust leak at the manifold/head gasket, a cracked exh manifold, or a blown doughnut gasket.
A lot of times, the heat after warm-up will expand the parts and make them seal better.
If you power-brake it, does it get a lot louder? An exh leak will.

You can check for a leak using a 2-3 ft long piece of vacuum hose.
One end in your ear and probe around the exhaust manifold with the other end. Works really well.
You can also insert some soft metal tubing in the "probing" end of the hose to control it a little better and keep your fingers away from the hot stuff. Bend the tubing 90 degs to check the underside of the manifolds with it.

z28onTweenkies

hmm, took it for a cruise tonight and it didnt seem to have any problems at all. this is a stupid problem that just decides to come and go as it pleases. come to think about it now, a while back i did over rev it a few times a while back. i will check the power brake trick and also the probe to hear things. my oil gauge reads zero, but the wierd thing is it goes up to about the first little notch in the orange when its warming up. the shake that i was talking about is not too serious, its just a little shake that will come here and there. whats so bad about rod knock and what exactly is it? and also a spun bearing?

z28onTweenkies

now that ive searched all of the archives, some of the problem can probably be fixed by properly setting my float level. i rebuilt the top half of my carb, and bought a new float, slapped it all together but never adjusted the darn thing. that would explain the off idle performance, but it wouldnt explain the tapping sound. does any of this sound right?

Arawn

This is a little odd, but my dad's 75 CJ5 has a rattle that's kind of similir, but it's caused by his "homemade muffler brackets" he made in an attempt to quite down the jeep. That's what he gets if you ask me, that jeep kicks ***. It'll rumble the windows and my desk on the other side, upstairs part of my house when it's idling on the street Oh well, when I get the new engine for my s-10 I get what ever flowmasters he had for it..

TransamGTA350

iTrader: (2)

Try replacing the rocker arm nuts and resetting the valve lash. The rocker arm nut on the exhaust valve of the #6 cylinder had a tendency to loosen up on both my 86' 305, and my friends 84' 305. It would tap in the morning, or cold weather.