spark knock, rattle

[gt fast]

i got a 92 ford explorer with the ohv im guessing. my problem is during hotter days or driving uphill i get a lot of spark knock( the pennies in a can sound). ive tried everything i can think of, ran diff brands/octanes or fuel, ran a full can of sea foam threw the brake booster vacuum hose, few weeks latrer i ran a can threw the throttle body port underneith it. it sounds better for a day or two then goes right backj to noirmal out of no where. it is driving me insane and i really want a fix to it. my MAF was replaced about 5 months ago. my truck is from phoenix arizona where the sound was barly there ever, i drove here to denver co0lorado and it is terrible. ive unhooked the battery for a whole day and it didnt change, my truck feels and sounds like its dieing. please help me.

 

[something9000]

try some good fuel system/fuel injector cleaner always makes mine run better.

 

[exhaustoboy]

Run super unleaded. It'll cure it. Seriously. early gen explorers were not designed to run on 87 octane ethanol blend fuel. It's crap. Super'll cure it, and you'll pick up a couple mpg's as well.

 

[FIND]

Run super unleaded. It'll cure it. Seriously. early gen explorers were not designed to run on 87 octane ethanol blend fuel. It's crap. Super'll cure it, and you'll pick up a couple mpg's as well.

Super unleaded is ethanol blended. Regular unleaded is generally what is not blended, that or premium. A 10% ethanol blend will not cause anything bad on an explorer except slightly worse mileage.

Explorers were designed to run on 85 or 87 octane fuel, and as you notice, he has tried different grades of fuel.

His problem is most likely due to the elevation.

OP, try pulling the SPOUT connector and see if that cures your knocking. You don't want to continue to drive with it out cause your mileage will go to crap. Pulling it disables the advance on your timing. You can find it back near your diagnostics port in the passenger side near the firewall. This is what it looks like:

 

[gt fast]

ok yea ive tried 85 87 89 and 91 grade fuels. had a shop do the fuel sytem clean and i also did one myself, i even ran a bottle of lucus fuel injector cleaner with only about maybe 2-3 gallons of fuel in my tank. same problem still occured. i drove my truck around for a about a day without the octane booster/ pin that you have described, the little grey block makes it barly run but does cure my problem for the most part, so what else could i do and why would i pull it out if its not good to drive with it out

 

[Roadrunner777]

Engine knock results from either a lean mixture condition, too high compression, or bad timing.

Lean mixture: Be sure there are no leaks from the MAF through the intake manifold. There is history of cracks and leaks in the rigid black plastic hose across the radiator. Extra air = lean mixture.

Also, verify your fuel pressure is 30PSI or better. Not enough fuel pressure means poor spray pattern and insufficient delivery. Not enough fuel = lean mixture.

High compression: You have pretty much played that one out with all the seafoam stuff. Moving forward on this gets expensive fast, it means manual decarbonizing the chambers, i.e. heads gotta come off.

Timing: check out the crankshaft position sensor at the front of the crank. Make sure it's not damaged, or mounted strange.

Some knock is spec for this engine, says so right in the owners manual:

"Do not be concerned if your vehicle sometimes knocks lightly when you drive up a hill or when you accelerate".

All else fails, run some octane booster. I'd do that before I even started thinking about tearing the heads off.

I guess I would throw in some new plugs and run 3,000 miles, see what they look like. Run a cooler range plug maybe.

Might run a cooler thermostat... make sure the cooling system is good.

 

[ricco750]

Try an new MAF sensor.

 

[gt fast]

ok thanks. i installed a new mass airflow sensor about 4 months ago. i also have pulled the heads already twice this year once couse i broke a valve and second to replace the rods,rockers and lifters. the carbon buildup isnt bad in the interior of engine from whjat we saw, it was after a can of sseafoam as well though. in anyway do you think since i am running a cold air intake it could be to lean now, i have a cone filter from spectre and a pipe from a civic we bent a diff direction. i figured the bigger pipe and filter weould help some for the thin air up here in the mountains but i could very well be wrong. i did pull my octane booster chip today and in all honesty about 75% of the rattle is gone, i do not notice any bit of a power loss and my fuel doesnt seem to be any worsse then it was before, so it coulkd be my fix.

 

[gt fast]

and for the record i dont ever notice any change with octane booster, i mean its a 19 gallon tank to a 12 oz bottle, thats less the .5 ounces to every gallon, if anything it would take 85 octane fuel to 85.001 octane, waste of money.. now if you were to add the 12 ounces to like 5 gallons of fuel you may have about 91 octane i your tank now, might as well run 91 from the pump.

 

[something9000]

the intake should be a problem as long at its sealed after the mas. and sounds like that chip thing might have been the just enough to cause a problem adding to the thinner air at your altitude.