So as the title states...I blocked off my egr, because it was sticking open, and thought this could be causing my code 52...any way...put it all back together and fired it up..and knocking like hell, sounds kinda like an exhaust valve. Did I do somethin wrong? The motor sounded fine before I removed it, It had no power, but it didnt knock. Any thoughts...maybe I forgot somethin?
Thanks, Jim

 

Bumped

 

Well duh. The EGR helps improve the apparent octane rating of the fuel. You're gonna have to use the more expensive gas or retard the timing.

 

I have been running high test for a while(due to codes 52, and 71), and after it started knocking ..I checked the timing and it was at 12 dbtdc, so I retarded to 5 datdc, and no change, besides...this is not a ping or what pre ignition sounds like...it sounds more like someone is pounding on the motor with a hammer.

 

Is there any chance that something dropped down the intake when you did this?

 

I guess its possible that some carbon went down there, the egr inlet pipe was caked with it, almost like creosote, but I would expect that to burn off, other than that...I cant think of anything that would have fallen in, I didnt take the plenum off, just the egr and inlet pipe. I am leaning toward exhaust leak at this point, others have said that an exhaust leak could cause...or sound like a knock.

also... did a compression test a couple weeks back the numbers were:

1= 175 2= 175
3= 170 4= 165
5= 170 6= 176
Those are not ideal #'s.. but I think they rule out a spent valve.

 

I don't think carbon is solid enough to cause a knock. It breaks up rather easily. It almost sounds like a bolt or a chunk of metal went into the intake.

 

Yeah...thats what it sounds like...but I cant think of how a bolt or a chunk of metal could have got in there...I would have had to put it in there on purpose, any confirmation on an exhaust leak at the manifold causing a knock? That is where the egr tube bolts on. And the more I think about it, the more I think that it was not sealed real well.

 

Can you put it back the way it was and see if it still makes noise?

 

Yes, I can...and after I check out the pipe coming from the manifold, and make sure it is sealed...that is what I will do...tho of course, it will not be exactly the same, as I cut the inlet tube going into the plenum to seal it.

 

You should be able to feel the exhaust pulse puffing around the leak pretty easily if it's making that much noise. Are both end of the old egr connections blocked?

 

5*btdc? That's way retarded for a 3vze. Should be 10*.

When was your last valve adjustment?

Ooops....noticed "exhaust leak". That could cause knocking.

 

Actualy..I set it at 5* atdc because of the knock, and it made no change, so back to 10* btdc it is, this truck has never had a valve adjustment.
And thank you, I was hoping someone would confirm that about the exhaust leak. I couldnt work last night (g/f told me I need to spend time with her< and she's jealous of my trucks..lol), so I'll get on it this weekend!
Will def post my results, and I am still hoping this also fixes my cel 52.
Thanks, all

 

You should really get the valves adjusted. They burn easily on these motors.

 

Yeah, eventually, I am going to pull the whole motor, and rebuild it, I have another motor in my garage that only has 130k on it, so I will just swap that in, and start working on this one. Untill then....I would love to do a valve adjustment, but from what i understand, it isnt something I can do myself(special tools, shims...that stuff scares me!), and I'm sure the machine shop would charge an arm and a leg, and I have already given my arms and legs to the oil companies...lol...next up...my oldest kid.

 

Turns out it was an exhaust leak, It was leaking at the pipe that comes off the manifold, and for some reason, sounded like a bad valve knock. Its all tight now, and no knocking...
However, I still get the code 52....I have a feeling that, I have a vacuum leak at the intake, because it surges at times now, and I didnt put the rtv to it last time I put it back together. guess thats the next step to fixing the code 52.