knocking oh no!

[greyrealsteam]

for the past year, ive been hearing a knocking sound in my v6 89 RS. 2.8, the wierd thing is, i would shift from first into 2nd, then 3rd, then from 3rd into 4th i would hear one big knock, but the car runs great. lately the RPM gauge has been inaccurate, and jumping around alot, and at start ups the oil pressure gauge jumps. but its been chugging alot during the take off, and when i flore it. i hear a sort of rattling sound, but not from the top, when i bend down and look under the car, the sound is clearly louder and more notticable from under the car. does anybody know what this could be caused from? hopefully not a rod or main bearing,

the car has 97 thousand miles, ODO hasnt rolled over.

-- edit --

the knocking sound sounds like it could be going as fast as the crank

[FormulaLT1]

Does it make the knocking sound in each gear at the same rpms?

[greyrealsteam]

well, when i take off, it chugs and feels like its about to die, but when it gets up to speed, it cruises. when shifting into gears it happens.

im starting to think its the clutch.

[wrightz28]

Try and locallize the knock. I had a nasty knock and low power on my old caprice that I thought was the end of the motor and it ended up being a stuck EGR.

[instantkevin]

sounds like a bearing to me.

consistent with engine rotation, and oil pressure fluctuates. very likely due to failed internal engine component.

but i's odd that you get a knock every time you go into 4th gear. maybe you have two seperate problems.

[89IROC&RS]

tough one, but id say it does sound like multiple problems, which tend to happen when you ignore a knock for a year......

[greyrealsteam]

well, it would knock once a in a great while. but recently i took it to my engines class, and the timing was way way off, so we fixed it and that knocking sound, was actually missfire. but the thing is, i looked on all data, and the timing is supposed to be on 10 degrees north, but it runs like crap when i do it that way. when i adjust and turn the rotor by ear, i have somebody in the car telling me when the RPM gauge smoothes out, and then it runs great for awhile, then goes back to crappy. the cap plugs and wires are pretty new. less than year old, i havent replaced the rotor, and im thinking thats what the problem is, but im not for sure. im still workin on it today. hopefully i can get it done.

has anybody know how to fix this problem, or has anybody had this problem??

so to re cap:

RPM gauge innaccurate,

i adjust timing, works great for 15 mins. goes back to crappy

--- edit ----

for the knock that i heard once in a while, it woudl hear only one single knock and that was it, and that happen like every one or 2 months, so i just thought it was nothing.

runs good slow speeds, when i put a load on, it chugs and has no power.

and thats pretty much it.

[greyrealsteam]

ok, so i figured out the problem, i wasnt disconnecting the line to the distributor when i was timing it. so that was one of the problems. the other problem was a leaky egr valve. i did a propane test and found that it was leaking.

[89IROC&RS]

well done, i was starting to wonder if you had a stretched timing chain or something. carry on.

[greyrealsteam]

problem fixed.

bad EGR valve.

now its time for advanced timing!!!

how much advanced is good for good performance?

[89IROC&RS]

stock setting, best for performance gotta love computer controlled advance curves.

[wrightz28]

eh, I heard you can bump about 4 adv. on the 6'r.

[silicon212]

89IROC&RS is absolutely right. Set it at the stock setting - the computer will handle the best timing for the engine under all conditions - EST and ESC are your friends, my friend. ESC and EST together will run the timing as advanced as possible without incurring detonation.

You can bump it to a more advanced static timing, but the computer will retard it in compensation and you will be exactly where you started.

--

On the original topic, a stretched timing chain can certainly produce a knocking sound which sounds as though it's coming from the bottom end. Amazingly, so can the EGR as I have had this happen to me, too. Must be fairly common. In my case, it was the gasket under the EGR valve - and the exhaust leak was the source of the "knock".

My current car, an '88 caprice 9C1, has a "knock" when idling - but it's actually the heat riser butterfly in the passenger side exhaust manifold making that noise so that gives you something else to look into. One question for you - you said it knocks in 4th - is this when you have it under load or at all times? How is your oil pressure? A worn or spun main bearing will knock with a dull thud when under load.

[greyrealsteam]

ah, thanks friends. hey i found something out today when i was fixing my car, earlier i said i had very bad RPM readings. the needle was jumping around alot, even after i fixed the EGR valve, it jumped, and bogged a little bit. so i looked at the wire going from the coil to the rotor cap, and i could see sparks coming through the plastic and it looked like lightening, so i replaced the wire, and the RPM was fixed. so if anybody has a jumpy rpm gauge, most likely it would be directly related to the rotor cap and wires or coil or coil wire! just want to say that.

later

[flatlander757]

Did you remember to troubleshoot the sphincter bypass valve as well? It's on the exhaust side and makes a nasty noise if it's stuck open.