Engine Knock, but not the usual

[jtb1689]

Let me first apologize if this is in the wrong place, 1 year reader, 1st time poster.

I have a '93 Explorer EB Sport. Recently i noticed the engine knock under load, in overdrive up hill, hotter weather, the usual right? Of course the first thing I did was hit these forums and find out what there is to do about this. Well... I followed the Ford recommended procedure for carbon cleaning (3 times of carb cleaner and 4 miles of 3000 rpm and so on), nothing. Didn't even get better, no change. I cleaned the MAF, twice, once before the carbon cleaning and once after. Nothing. I checked every vacuum hose I could and the intake manifold, no leaks. So the 3 ways I have read over and over to cure the knock issue have not helped, I'm wondering if anyone has any more or better ideas. She's got about 120K miles and is stock except for the KKM Tru-Rev and a Flowmaster Force II cat-back. Thanks for the help.

 

[boggs1227]

is it a knock or a ping under load ?? could be that the lower intake gasket has let go and not sealing the upper part of the intake system .

 

[freeridejunkie87]

is it the factory catalytic converter?
if it sounds like a rapid rattling kind of knock, the cat could be suspect especially if you say it happens under load. sometimes after a lot of miles the catalist materal breaks loose and rattles around (sounds like a bolt in the exhaust or something) under load.

so drive on a road with a long wall next to it or sound wall of some sort when the roads are empty, get up to speed and cruise, then go WOT and listen to see if you hear the "knock" or ratlle. you should hear it when it downshifts and the RPM's go up.

if it was a ping you would notice a serious change in power output. an engine knock sometimes goes along with low oil pressure.

you can unbolt the cat and check to see if anything falls out.


noises are always tough to find. good luck

 

[jtb1689]

I guess it would be more of a ping, it's not quite as deep as a knock. But it sounds more like it's coming from the front of the car. However it's a new noise and you could be right about the cat. My only question is when you say I should hear it when I downshift and the rpm's go up, do you mean the ping should stay after the shift and as the rpm's go up, or disappear once the car is done shifting? Because I have noticed, as the ping begins (which I get most often at low rpm's in overdrive on a slight incline at around 60 mph) I can put the pedal to the floor and just as the car shifts it pings really bad, then goes away completely as the rpm's get up. I appreciate the help, it's always nice to find another point to start working on when everything else I could think of was not helping to fix or diagnose.

 

[boggs1227]

plugs and ignition issue ??

 

[jtb1689]

first thing i checked. everything firing perfectly

 

[HahnsB2]

Your 93 happen to be a Cali model with EGR? If so I'd check that.

 

[freeridejunkie87]

the noise im talking about you would hear under a slight load and would get louder as you accelerate more, when it downshifts it would be louder.

also if its a cat you could have power issues as well. could be constant or intermitent. might seem like the truck is bogging down every now and then. but thats not always the case. im just curious

 

[jtb1689]

Definately not the case. As I accelerate it gets faster and louder, but if a downshift occurs the pinging peaks in loudness and speed but then is gone. My worry is it is obviously getting worse as today I noticed the pinging with hardly any load, just normal cruising with a slight acceleration at low speeds (around 30 mph). With the windows down I noticed it to be coming from either the engine or possibly lower down toward the bottom of the exhaust manifold(just as a location/reference point of sound, that's not to say it has anything to do with the exhaust manifold or even came from there). I will be checking for anything loose but any ideas if it is indeed coming from the engine? Besides check for vaccum/intake leaks, clean MAF, and carbon bust the engine.

P.S. Not a california explorer

 

[jtb1689]

Pulled the octane shorting pin/plug, helped a little bit. A lot less pinging but still there here and there. Checked the cats, no problem there with loose catalyst material. Any other ideas guys? Maybe switching out the computer with another '93 explorer that doesn't ping?

 

[mawrazen]

Vacuum leak or bad O2 sensors?

 

[jtb1689]

As I said earlier I've already checked all vacuum lines. As far as O2 sensors go, if one were to fail wouldn't my check engine light be on? I also have no actual testing equipment for the computers and all that so I guess just replace them and see if it makes a difference?