Spark KNOCK!

[1994RangerMan]

My Ranger has a few problems as you guys may have read on the board.. It is a good truck but has these little problems that just dont seem to ever to away..

My truck spark knocks unless i put midgrade or high grade gas in it..

I was told i could get the computer reprogrammed and that may fix it. i was also told the timing could be off.. Evidently my truck does not have a knock sensor according to the mechanics.. we looked it up.. cant find a part for it..

Any help will be appreciated..

Thanks

[EVH5150]

I would also guess the timing is off.

[freeclimber]

Ford has had a lot of problems with their DPFE sensors, which control the EGR cycling.
A somewhat easy and FREE thing to try is to clean the EGR port in the throttle body. While you've got the EGR off, start the motor and let the EGR tube blow any loose debris out.
You might be able to see the carbon accumulation just by taking intake tubing off and looking into throttle with plate held open.

[BeachBoy]

Did you ever solve the Spark knock problem on your Ranger? I have a 1994 4.0/AT and am having the same problem. I do not have to accelerate hard to get pinging, and if I go up hill even out of OD, I still get it at 30 mph and higher. I don't find any way to adjust the timing.

Any help you can give would be appreciated.

Thanks

[1994RangerMan]

no i have not found anything yet on the spark knock. I wish i could.. u find anything yet??

[BeachBoy]

I spoke to the original owner and was told that the truck started to need mid grade or premium to avoid pinging about 18 months ago. Second point, I have not tried the suggestion you received to your original post about cleaning/purging the EGR line, but I did open the throttle plate and look down the body with a strong flashlight and saw quite a bit of carbon along the right side near where the EGR tube screws in. Why carbon might cause a ping, I do not know.

Until I get to trying that I am just going to use the higher octane gas. If it 2.45 or 2.55 as opposed to 2.35, that not a lot to eliminate the ping.

[1994RangerMan]

that is the same thing i have been doing.. sometimes i still get the ping with the midgrade..

[1994RangerMan]

anybody have any ideas yet about this spark knock problem.. i took the intake off and cleaned all the carbon out..

[BeachBoy]

Originally Posted by 1994RangerMan

anybody have any ideas yet about this spark knock problem.. i took the intake off and cleaned all the carbon out..

I have looked in past the throttle plate down toward the place where the EGR plugs in and can see a lot of carbon. I am wondering if your carbon clean out helped reduce the pinging problem. I am running midgrade and now and most but not all of the knock has gone away.

[1994RangerMan]

i was told to put in a better spark plug..like a expensive one that sparks easier/earlier. this should solve the problem..

[BeachBoy]

Originally Posted by 1994RangerMan

i was told to put in a better spark plug..like a expensive one that sparks easier/earlier. this should solve the problem..

Please let me know if the spark plugs help. I am running stock Autolite and have pulled the plugs and see nothing unusual. Could it be that there is carbon inside the heads and this is increasing compression? If so I wonder how to get it out without throwing in something that messes up the catalytic coverter? Did cleaning the carbon out of your intake help?

[1994RangerMan]

cleaning the intake helped some.. i have the same autolite plugs you have.. i am sure there is a bunch of carbon built up in the heads.. some garages will clean all that stuff for a price.. some say like 100 bucks + .. no exact cost..

[sp3edr4cer]

Mine did knocked when i put a chip in it and only ran cheep stuff in it. and i could never get it fixed. But the weird thing is after i blew the engine up i replaced the engine and started running cheep stuff from the start and it has never knocked again. I was told all you have to do is run one take of good stuff through the truck and it reprograms its self for the high octane but you cannot go backwards with it
so my new engine has never seen high octane and never will

[freeclimber]

The EGR regulates the amount of exhaust gas that is allowed back into the cylinders for combustion. The exhaust gas is low on oxygen and displaces space that would have atmoshperic oxygen content. This reduces the amount of combustion capable and has the effect of cooling the combustion chamber. Spark knock is caused by pre-detonation (effected by advanced timing, reduced combustion chamber volume--carbon buildup--which results in higher compression, cylinder temp too high which ignites fuel before spark w/ the help of compression forces. Faster firing spark plugs will not fix the problem. If your truck is spark knocking w/o a service engine light on, the first thing to do is check and clean the EGR port. Even if it isn't the sole cause, it contributes and needs to be cleaned regardless.
These trucks don't have adjustable timing. The PCM makes adjustments based on sensor inputs.
A second common cause (it really sucks) is a bad MAF sensor. The sensor can give bad PCM input without triggering the service light and can even pass a scan tool test w/o showing bad. You're left with either swapping a known good part or just replacing it ($$$$).
The sad fact is that w/o the help of at least an OBDII code to guide you along, you need to have an expensive scan tool or you're just left guessing and replacing parts.

[BeachBoy]

Freeclimber,

Thanks for your informative post. I have heard that you can help reduce spark knock by resetting??? the engine computer. Is this correct and if so is it as easy as disconnecting the negative terminal on the battery for 30 minutes? I have run two full tanks of Moboil super premium and I still get an occasional knock.

How do you clean the EGR port without a lot of fancy tools? Is there any clemical like a spray in carb cleaner that will help? Any other relatively cheap fixes. At $4 per tank extra for super premium, I am willing to try other things.

Thanks again.

BeachBoy