intermittent knock?

[231_natural]

I have an 83 231 non-ccc. Usually runs great when driving normally, but when I hammer on the gas the engine make a intermittent knocking sound during acceleration. kind of like it's out of tune. It is tuned up correctly, with new wires and plugs. If you guys have any idea what this might be please let me know.

Thanks in advance,

 

[231_natural]

okay, when i'm coasting at about 25mph with my foot of the pedal and then quickly give it about 3/4 throttle the car hesitated slightly and makes a knocking/deisling sound and then the tranny shifts, the engine picks up and the sound almost completely goes away and I get smooth acceleration.

 

[Freddie's Buick]

I think that sounds like detonation knock. You've ripped off all the CCC stuff right? If you did.....you'll have to figure out how to tweak the engine to combat knock without the assistance of an electronically controlled knock sensor. (You've disabled that system).

The EGR is also electonically controlled, so you'll have to back-date an EGR system too. (Disabling the EGR promotes detonation).

It's a pain in the arse with the CCC stuff installed so it'll be a killer tweaking w/o it. You'll have to build her up some more. Probably an after-market vacuum advanced distributor with adjustable centrifugal weights. New cam and timing chain. Also, you'll have to back-date to a non-CCC carburetor if you have'nt already.

 

[231_natural]

Sorry should have specified. It's a Canadian built engine and came from the factory whithout the computer. The Egr is vacuum operated. There are some cracks in some of the lines though and i will be replacing them today hoping that solves something. The engine used to run great, it's just been the last few months that this grating noise started. Thanks for your response.

 

[Freddie's Buick]

Any leaks in the EGR will promote detonation....:biggrin:

 

[231_natural]

Thanks alot Freddie

 

[texasturbo]

Determine if it is detonation.. it probably is, so back the timing off a little. Maybe 4 to 6 degrees, check the boost level.. Add a bottle of 102 Octane booster. Then see if the knock goes away or is at least considerably less..

Work from there........

 

[BADAZZV6]

Sounds like a vacuum leak to me or a weak EGR valve. Inspect and replace those questionable vacuum lines. Spray the intake gaskets, carb base, carb butterfly rod (sometimes they wear the bushing and leak) with WD-40 or something to check for changes in idle RPM. You might try disconnecting the vacuum line to the EGR (make sure you plug off the vacuum line) and then take it for a drive. In my experience, hesitations are typically from vacuum leaks/EGR valves.

Maybe the EGR port in the intake is blocked with carbon. You might take it off and inspect the port.

 

[231_natural]

Figured it out. The TV cable was out of adjustment, which was throwing off the shifts.
Thanks for the suggestions. I disconnected the egr valve and the engine ran just fine. I had heard that without the egr hooked up it would cause detonation. So it is good to know it won't as I would like to put a edel intake on that is not egr equipped.