I have developed a spark knock when the engine is above 200*.
When it happens, the ecm retards the timing 20*, but it still does it. If you stay on the throttle the ecm sets a knock retard of 12* and sets code 42 and 43. The knock sensor and esc are fine. I ran my car on Datamaster and didn't see anything that was radically out of shape. But I am also not sure what I should be looking for. I have tried adjusting the timing and fuel pressure, but that didn't help.

Any suggestions?

 

have yoiu tried higher octane?

 

I have tried using 104 octane booster with 93 octane pump gas. Didn't help.

 

Hate to say it but on an engine that old it could very well be a "mechanical" knocking, ie rods, main bearings etc.

Try running a good fuel injector cleaner and amaco premium gas and see if it goes away.

 

The engine has less than 25,000 miles on it. It runs fine untill it reaches 200*. Wouldn't a mechanical problem be there no matter what the temp. of the engine is?

 

Does your computer know you removed the EGR? Sounds like it's trying to advance the timing because it assumes that the EGR is operating properly and the temperature in the chamber has dropped enough to allow more advance. It may be that because your EGR isn't there, it's advancing the timing without the drop in temperature which results in knock and the EST system to kick in. Try putting the EGR back on and see what happens.

 

I removed the EGR after this problem started because I was told that the EGR might be the cause of the problem. The problem persisted after I removed it.

Any other ideas?

 

EGR is there to reduce knock.

 

Was the egr working properly when you took it off, any codes? Does anyone know if it is a simple change in the chip to let the computer know the egr is gone? My egr system was all jacked up when I first bought this car and it got spark knock, I replaced the valve and solenoid and it went away along with the code.

 

I think it is the absence of a properly working EGR system that is causing your problem, and removing it didn't really change anything. I think that before you do anything else, you should make sure that the EGR components that you have work the way they are supposed to, and make sure that nothing is clogged to prevent its function.

 

My car does the same thing. It has a EGR and a new knock sensor. I broke the old one. When the car is cool it runs like a champ. when it heats up it knocks. WHat can I do?? And yes the temp is 200* as well.

 

The only time it throws a code for the EGR is when I am running down the interstate about 80mph with the a/c on.

I don't know if the EGR was functioning properly before. I know that it didn't have any vacuum leaks. Can I check the EGR passages in the intake for clogs before I re-install it? What else should I look for?

I don't know if this has anything to do with the same problem, but it runs really rough when started cold.

 

It was probably the solenoid, I'm sure there is a way to test them but I was lazy on mine and replaced them both. I'm sure the passages are fine, just look at the plenum when you have it off and the base where the egr valve sits.

 

Not to hi-jack this post, but I would like to know if it is a simple change in the chip to disable egr and if that would eliminate timing advance at cruise ( if so ITS LT1 TIME FOR ME )

 

Yes it is, BUT, the LT1 handled EGR internally through valve overlap in the cam.

 

Cool thanks, but I meant lt1 intake swap!

 

When I figure out why mine's not working, I'll let you know. Try this test though and see what happens- put the car in park, rev it to 2500-3000 RPM and hold it there, then bypass the solenoid with a vacuum line so that you have a line going straight from the source to the valve, then disconnect and reconnect the vacuum at the valve. If it's working, the engine speed should change.

 

my car does the samething (86 iroc 305 tpi)...it runs great when its cool but when it hits like 200* its over..i get the last boost and then the timing retards to where the car will barely move out of its own way...i changed the knock sensor and the esc module so far and i am still getting the code 43...any ideas?? if anyone finds an answer let me know..

 

I replaced my EGR last weekend and it didn't help my problem. I can't find anything out of the ordinary when I run it on Datamater, but I really don't know what I should be looking for. I would gladly give $50 to whomever can solve this one for me.

 

I don't think you're going to have an easy fix here.

First thing I would do as a diagnostic procedure is figure out if it's real knock or not. To disable the Knock Sensor simply run the KS wire to a 3900 Ohm resistor ($.25 at Radio Shack) and then on to a ground. This will deactivate the KS completely- it will think the sensor is there but there will never be any knock registered. You will want to reset the computer after you do this becuase it remembers when and where it heard knock before and it would take about an hour of driving around to work the knock retard learns back down to zero again otherwise.

Now that you have full timing with no retard under any circumstances go take a spin. Get it up over 200* and listen for knock. If you hear knock then the knock retard system was correctly "hearing" and reacting to knock by pulling the spark back. If you DON'T hear any knock, then there is a problem in the KS system (electronics) somewhere.

Not a fix, but a legitimate diagnostic procedure to cut the possibilities at least in half.

 

Well it turned out to be an easy fix after all. My uncle, who is a mechanic halfway across the country, told me over the phone, to replace the Bosch O2 sensor with an AC-Delco.

Problem solved.:lala: