Hey guys, Just looking for some advice on what to do with my 97 f150 .

I have an engine knock at light load (ex. going up a small hill on highway). The noise is present above 65mph on flat ground. Not sure how to describe the noise. all i can say is that it is not an exhaust tick or ping sound. The noise resembles a rattle/knock. It gets louder as speed/accelerator increases. No noise at city speeds unless under 3/4 - full throttle. Burning a bit of oil, approx. 1/5th liter per tank. after an hour or so of hunting at speeds of 1-3 mph, I will idle in park for 5 minutes (to shoot the animal). I get a puff of blue smoke after putting in drive and pushing on the gas peddle (less than 1500 rpm). slight vibration at idle 50% of the time warm or cold + rough start 10% of the time warm or cold. Engine temp. gauge sits slightly under half and oil pressure is slightly above half

I changed the EGR valve, plugs and wires and fuel filter with no change to symptoms. While changing the egr valve, there was no "pop" from removing the vacuum line @ intake. Also, I noticed a sucking/whistling noise coming from the EGR solenoid for about 30 seconds after I turn off the engine that is only audible with the hood open. I just did my first oil change. not sure what the previous owner had in there, but i put 5w20 mobile 1 synthetic due to cold canadian winter. I also used 1/3rd bottle of lucas oil stabilizer to oil and lucas injector cleaner.

- clean K+N air filter (oil type)
- MAF sensor (replacement? or clean?)
- PCV valve
- check timing?
- check vacuum pressure?
- check for clogged cat? not sure how

any advice would be greatly appreciated.

Thanks,

~Kyler

 

Does the knock go away or lessen if you use premium gas?

 

I have not tried premium gas yet. What kind of problem do you think it would be if the noise went away with premium?

 

Spark knock. Usually due to excessive combustion chamber deposits if you don't have any DTC's. If it's burning oil, this is a distinct possibility.

 

I put premium in today and the noise is almost gone. I picked up some seafoam, do you recommend to put it in the vacuum, tank or both?

I also noticed some white sludge on the top of the oil cap. Any ideas on that?

 

Most people wont recommend seafoam, but instead a professional motor-vac cleaning

The white/yellowish film on the bottom of your filler cap is normal. Caused by condensation that doesn't get burnt off from short trips.

"Spark knock (detonation) is an erratic form of combustion that occurs when multiple flame fronts occur simultaneously inside a combustion chamber. Detonation occurs because fuel is subjected to either too much pressure, too much heat or both. It usually happens during acceleration when the engine is heavily loaded and cylinder pressures are at their peak.

Instead of a single flame front growing outward smoothly like an expanding balloon from the point of ignition, multiple flame fronts are generated spontaneously throughout the combustion chamber as the fuel automatically ignites from heat and pressure. The multiple flame fronts collide, creating shock waves that produce a sharp metallic pinging or knocking noise.

Mild detonation can occur in almost any engine and will not cause damage. Prolonged heavy detonation can crack pistons and rings, blow out head gaskets, damage spark plugs and valves, and flatten rod bearings.

Any of the following can cause detonation:

^ Too Much Compression: An accumulation of carbon deposits in the combustion chambers, on piston tops and valves can increase compression to the point where it exceeds fuel octane rating. If a top cleaner fuel additive fails to remove deposits, a new alternative is to blast the deposits loose by blowing crushed walnut shells through the spark plug hole. Otherwise, the head will have to be removed so the deposits can be scraped off.

^ Overadvanced Ignition Timing: Too much spark advance causes cylinder pressure to rise too rapidly. If resetting the timing to stock specifications does not help, retarding timing a couple of degrees may be necessary to eliminate knock.

^ Engine Overheating: A hot engine is more likely to suffer spark knock than one which runs at normal temperature. Overheating can be caused by low coolant, a defective fan clutch, too hot a thermostat, a bad water pump, etc. A buildup of lime and rust deposits in the head and block can also reduce heat transfer.

^ Overheated Air: The thermostatically controlled air cleaner provides the carburetor with hot air to aid fuel vaporization during engine warm-up. If the air control door sticks shut so that the carburetor continues to receive heated air after the engine is warm, detonation may occur, especially during hot weather. Check the operation of the air flow control door in the air cleaner to see that it opens as the engine warms up. No movement may mean a loose vacuum hose or a defective vacuum motor or thermostat.

^ Lean Fuel Mixture: Rich fuel mixtures resist detonation while lean ones do not. Air leaks in vacuum lines, intake manifold gaskets, carburetor gaskets or fuel injection intake plumbing downstream of the throttle can all admit extra air into the engine and lean out the fuel mixture. Lean mixtures can also be caused by dirty fuel injectors, carburetor jets clogged with fuel deposits or dirt, a restricted fuel filter, or a weak fuel pump.

The air/fuel ratio can also be affected by changes in altitude. A carburetor calibrated for high altitude driving will run too lean if driven at a lower elevation. Altitude changes are generally compensated for on computer cars by the barometric pressure sensor.

A lean fuel condition can be diagnosed by watching for lean misfire on an ignition scope, or by using a four-gas infrared analyzer and watching exhaust oxygen levels. A reading over about 3% to 4% oxygen would indicate a lean fuel condition.

^ Spark Plug Too Hot: The wrong heat range plug can cause detonation as well as pre-ignition. Copper core plugs are less likely to cause detonation than standard spark plugs.

^ Loss of Exhaust Gas Recirculation (EGR): EGR keeps combustion temperatures down, reducing the tendency to detonate. If the EGR valve is inoperative or someone has disconnected or plugged its vacuum hose, higher combustion temperatures can cause pinging.

^ Low Octane Fuel: Burning cheap gas may be one way to save pennies, but switching to a higher grade of fuel may be necessary to eliminate a persistent knock problem.

^ Defective Knock Sensor: The knock sensor responds to frequency vibrations produced by detonation (typically 6 - 8 kHz), and signals the computer to momentarily retard ignition timing until detonation stops. A knock sensor can usually be tested by rapping a wrench on the manifold near the sensor (never hit the sensor itself). If there is no timing retard, the sensor may be defective."

 

Just an update.. I changed my K&N oil filter to an OEM paper filter and the noise is completely gone.. My guess is the computer didn't know what to do with the extra air..

 

Several things are a hint to the issue.
If the K&N was blocked it was 'restricting air' and sucking more oil by valve guide seals that you saw the puff from.
Oil in the mix can cause ping as well.
Another item you mention is the noise from the EGR.
I would clean the filter under the cap on the EVR solenoid.
It sounds like the EGR is slow to release back on seat due to the filter being plugged and will also cause pinging and knock because it also advances igniton timing and leans the mix when OX sensors detect the lean mix.
Don't use the K&N. You are not getting any kind of benifit from it.
Good luck.

 

The K&N oil has also been known to foul the MAF sensor - I'd recommend you clean it now that you have the filter out of there. Your intake may also be dusty and the throttle body may be gunked up.