After going thru a lengthy search to correct engine miss/shutter at low RPM [Rx was a new fuel pump], I am still getting a slight engine knock during hard acceleration [not quite WOT]. Using premium gas [though some rumors the octane is lower at this mega-travel center], and timing is set at 6 maybe 7 degrees. Most of the ignition system has been redone [eg, wires, plugs, disto parts, etc]. What am I missing?

 

check your timing

 

OldA--as indicated, timing is between 6-7 degrees--what am I checking for?

 

It shouldnt be pinging at that timing. Is it over heating at all? That will also cause "detonation", or "Knocking/pinging". I took mine to 12 before it even started.

You also may want to do a compression test. Your miss could be the beginning of a head gasket going bad. h

 

The 'mis' could be from a lot of things...even though you were just there start with the basics and go thru them all AGAIN, because we all "mis" things...

fuel pressure and stability

fuel injectors

ignition sys..timing, ICM connections and heat-grease

did anyone see the rotor that another member posted? He had a 'mis' as well...his rotor was not screwed down and had the tip bent 90 degrees.

The faster the engine revs the more precise the ignition must become. sloppy gaps/parts at idle may never be noticed...but at 4000 rpm under load they become obvious...or their presence becomes obvious.

Look at the wire stack on the jumper post. Those are all your power wires for the various control systems, ecm included. If dirty they send weak or unstable power..low voltage. Low voltage in the primary ign assures you of random misfiring. While we're at it,. go thru the harness grounds. Not the cable, rather the harness collection near the oil filter. This system operates on grounds, NOT power wires like most things. Ground path completion/disruption. Poor grounds make for poor control.

If you haven't already done so, going thru the plugs and checking gaps and looking at insulators don't hurt anything except your hands when you finally run out of excuses trying to avoid (praying you find the problem elsewhere) pulling the passenger side plugs...

 

Knocking can also be caused by running lean (high combustion chamber temperatures). A scan tool can tell you what's happening there. Look at the BLMs.

 

yep..Cliffs right. A stuck EGR may be responsible. If its unable to open & cool the burn...it';ll knock like a hari krishna

 

EGR does not operate at WOT.

 

Give us the operating conditions when this happens.
-Fuel pressure
-Operating temperature
-Does the scanner show any knock counts
-Does it knock at WOT

The more information the better because there could be many reasons for a knock and we can then rule some of the reasons out.

 

This car was a "rescue project" after a friend toasted the engine as a result of a ruptured radiator side tank. Over time, as part of the rebuild, I've replace nearly all of the ingnition related parts--from 02 sensor, to wires and plugs, to nearly all distributor parts, and even a wayward ECM. Omhs on the injectors were around 16 and I've been putting some injector cleaner about once a month, just in case. Since replacing the fuel pump the car has run pretty well--fuel pressure is 38 to 40, temps are consistantly in the 198 to 205 range, MPG on latest tank is over 21. Basically, the car runs and feels good--except for the modest knocking during hard acceleration, ie, nearing WOT with an auto tranny. Base on where I was a few months ago with the missing and shaking, and copious ECM fault codes--I am in a pretty happy place right now. My plan is to refill with premium at several different stations in the area to make sure its not a hidden lower octane thing. In the interim, I was hoping the "experience" here on the forum could give me some other ideas about the knocking that I could check-out/validate. Guess the bottom-line for me is--if it continues to run at its current state of performance, I'll probably call it "good enough."