Knock Sensor

[tedrisch]

I have a '99 Ranger 3.0 FlexFuel. It knocks under freeway driving with a load applied unless I run high octane fuel. I was told that the knock sensor was probaby to blame. Has any one else replaced this? I have seen other posts regarding spark knock, but no one seems to speak too loudly about this little sensor. I think if it is doing it's job correctly, then it can adjust the timing according to how much octane is perceived to be in the fuel.

 

[McCormack]

AFAIK 3.0's don't have knock sensors. Do a search for pinging and you'll find some solutions (clean your MAF; install a 180 T-stat; retard your timing with an X-Cal; etc.) to fix the infamous 3.0 pinging problem.

 

[evanesce69]

E85 has a higher octane rating than regular E10. The knock should go away with a higher ethanol content, unless the computer has miscalculated the ratio. It does this using a combination of various sensors. There is a sensor in the fuel system that calculates the "perceived" ethanol content of the fuel, then the actual content is homed in on using an input from the O2 sensors. The map is static based on these calculations. It's like x + y = z, where the x and y values are referenced on a table in the ecu and return a z value for ingition timing and fuel curve. The only way to change these values is to reprogram the ECU with modified curves for the timing and fuel or "trick" the ECU using an add on chip or module.

At least that is my humble understanding of the process. This is a brief synopsis of what happens. Of course there is more to it than that. There are also inputs from the fuel level indicator received at fill up that helps the ecu know whether or not it has to recalculate the z values.

I'll look later this evening for the reference material that I read on the inner workings of the ECU.





Rob

 

[tedrisch]

Thanks for the info guys. I was hoping not to have to 'trick' the ECU, but to fix the problem by tracking down a bad sensor or something of that nature. I guess my vehicle does not have a knock sensor so maybe i will try and clean the MAF and its probably a good idea to replace the O2 sensors, since they probably have never been changed in the truck's 123,000 mile life.

What is the sensor called that is in the fuel system that measures fuel content? Maybe I can check that guy.

 

[McCormack]

You don't really have to trick the ECU - all you have to do is get a programmer or a chip and retard the timing a degree or two and your engine won't ping anymore.
A 180 T-stat really toned down the pinging in my truck, and you also may want to check your DPFE sensor - they can be on their way to failing and contribute to pinging even if they're not throwing a code.

 

[evanesce69]

Smoke and mirrors

Most plug in inline chips either modify the input or output signals for the ECU. Modifying the input signals "tricks" the ECU into thinking it is under different conditions that actual. Modifying the output signals effectively "tricks" the driven devices in question, i.e. timing advance/retard, injector dwell time, converter lockup (for automatics). unless you change the actual reference values stored INSIDE the ECU's PROM then its all smoke and mirrors.


Rob

 

[tedrisch]

Thanks guys. I bought a cheap DPFE from autozon w/ a 3 year warranty. It failed twice in two years and throws the CEL when it does, so I think it should be ok for a while. I will try the 180 tsat next coolant change, wich is coming soon. Any other sensors I could check? It doesnt ping running on 93 octane, I wander if the PCM just cant tell the octane level in the fuel.............

 

[McCormack]

I don't know of any other sensors that you can check, so clean your MAF (or even replace it if you have the funds), try a 180 T-stat and a set of colder pugs (I use Accel 516's) and you should be able to use regular gas. If not then you'll have to retard your timing a bit.

 

[tedrisch]

Thanks againg guys- I have some MAF cleaner and will replace the t-stat soon. I'll keep you posted if I find a solution!

As for the plugs, I replaced them several months ago with new Motorcraft Fire wire plugs, gapped according to factory specs with no change in the Pinging.

 

[McCormack]

As for the plugs, I replaced them several months ago with new Motorcraft Fire wire plugs, gapped according to factory specs with no change in the Pinging.

Try a heat range colder... the colder plugs made a difference in my truck.

 

[tedrisch]

I am trying to fix the problem, not cover it up. I figure if the truck came from the factory not pinging, why should i have to install aftermarket parts to get the same results? Shouldnt the truck be able to run like new with some regular maintenance? If it ran fine before, why on earth would I need to re-tune the computer? It just don't seem right.

 

[evanesce69]

you are right, it doesn't seem right. If you can fix your truck without tricking it, then that is the best way to go. Unfortunately, not all problems have a simple fix. I hope yours does....

 

[McCormack]

Some vehicles like the 3.0 Ranger come from the factory with their engine's timing set right on the edge of pinging in order to get the cleanest possible burn for emissions purposes. But as an engine gets a few miles on it, it carbons up and the carbon insulates the combustion chamber (or possibly raises the compression ratio) and makes it run hotter, and in an engine that has it's timing set to the max that extra combustion chamber heat then causes pinging.
Other than running a higher octane gasoline some suggested ways to deal with the problem is to reduce combustion chamber temps via a colder thermostat and spark plugs, or to retard the ignition. In the old days of distributor ignition it was very easy to advance or retard an engine's timing with a twist of the distributor, but with todays computer controlled ignition you need to program the computer in order to change the timing - and programming a computer via a chip or programmer is really no big deal and nothing to be afraid of.
But if you'd rather not alter your truck then by all means leave it stock and live with the pinging or else the added expense of running premium gasoline.

 

[tedrisch]

I just changed the coolant and thermostat, The coolant was disgusting and black. The t-stat looked to be original; motorcraft. I had the coolant supposedly "flushed" at a radiator shop a little over a year ago because it looked nasty then, but it seems like if they did flush it out that it shouldn't have gotten bad this quickly. Come to think of it I am not even sure if they did anything to it..........

Just charged my $60, what an effin ripoff....

I also Seafoamed the motor, but little white smoke came out??? Def. did not cloud the neighborhood like I had hoped.

I am running a tank of Premium through it and will test it out on Regular when thats done and see if I have cleared the pinging..........

 

[tedrisch]

PS: it's running like a sewing machine right now..........