What controls engine timing in Crown Vic/Grand Marquis?

[Oleg Volk]

My engine knocks in hot weather when under a load. I tried higher octane gas, no change. Taking it to a mechanic when I first bought the car did not improve matters, either. Any suggestions on what to investigate next?

[charby]

Could have a weak exhaust valve spring(s) causing ignition in the exhaust chambers, had this happen on a 300 six in a ford I used to own.

[matis]

http://www.ford-trucks.com/forums/forumdisplay.php?f=35

Oleg,

I don't know if this is your problem, but it sounds like it may be:

The above url will take you to Ford-Truck Enthusiast.  Go to Ranger/B-series, then to the 2nd sticky: Technical articles....  There, about 5-6 down from the top you will find an article entitled: How to de-carbonize the 4.0 engine.

I was surprised to read how easy this is to do -- the instructions were taken verbatim from a Ford TSB, and this is embedded in a thread that discusses this problem.

It may be what is causing your problem.


If this does not solve the problem, I"d suggest you go the the Crown Vic/Marquis forum and look for threads that deal with it.

I hope you find an easy (and cheap) fix.

matis

[caseydog]

Question:  1997 Ford Crown Victoria 4.6 mileage: 62k.  My problem  is pre-ignition spark knock.   We can use several different kinds of gasoline but we must use 87 octane.  I don't of any way lower the timing on a D.I.S. Our service techs don't seem to know what to do. Any help will be greatly appreciated.

Answer:   The ignition timing is not adjustable.  Several things to try are de-carbon the combustion chambers, check oxygen sensor for lean condition and check knock sensor for proper operation.



Wish I was closer Oleg , hard to do over the internet.

Ray

[Oleg Volk]

One of my friends thought it was the knock sensor, then said that the car doesn't have one...but the manual says that it does. I am confused now...

Mine is a 1997.

[garyk/nm]

Oleg,
Go to your nearest AutoZone and ask them to do a code scan (free). This will show any sensor problems. If any codes show up, problem solved. If not, I would suggest  a product called Seafoam. It cleans the intake and combustion chambers of buildup. Follow the instructions to the letter, and I think you will be surprised (and pleased) with the results.  Also, run a bottle of injector cleaner through the system. Lucas is a good choice, as are others.

[Sindawe]

Oleg,

If your manual is genuine Ford, or Helm supplied one, trust that.  Better if you can physically locate said sensor.  I've heard good things about Seafoam for removing carbon from combustion chambers as well.  

Also, this site: http://www.bobistheoilguy.com/ has a great forum for information on internal compustion engines, additives, cleaners and the like.

[cfabe]

Oleg,
Go to your nearest AutoZone and ask them to do a code scan (free). This will show any sensor problems. If any codes show up, problem solved.

Easy on this. The error codes just indicate that there is an error condition. The appropriate action is not always to replace the sensor or sensors associated with the code. For instance, an exhaust leak can cause an O2 sensor lean code, but the fix is not to replace the sensor, but to repair the cause of the problem, the leak. Autozone offers this service because it sells tons of sensors for them.

As for oleg's problem, engine timing is not easily adjustable on your engine. The suggestions to use a top end engine cleaner are good, carbon deposits in the cylinders can cause hot spots which will cause knock. Also make sure you have the proper heat range spark plugs installed.  The EGR system could also cause this if it is malfunctioning. My uncle had a problem on an Explorer where the wires in the MAF sensor got dirty and were causing the engine to run lean (which increases cylinder temps and can cause knock), and his solution was to carefully clean the sensor.

[Gun Runner]

First, you might want to try the forums at:

http://www.crownvic.net/

One thing that can certainly cause knocking is the air/fuel mixture going too lean.  This is usually caused by a defective oxygen sensor or un-metered air entering the intake tract.  A faulty o2 sensor should normally throw a code though.  Check to make sure the spark plugs are gapped within specs.  If running higher octane (89-93) gas doesn't seem to help there are a couple more things you could do.  You could try running spark plugs a heat range colder (see: http://forums.modulardepot.com/showthread.php?s=&threadid=2218 for proper plugs).  You could also try a 180 degree thermostat, especially if you have a clutch driven mechanical fan.

A couple more...  Have you tried unplugging the battery overnight yet?  Remove the negative cable and just let it sit.   This effectively resets the EEC  to the factory setting and lets it start over.

You could try unplugging the Mass Airflow Sensor (MAF), it should be right downstream of the airbox. with a plug on it containing 4 wires.  Once unplugged the car will revert back to the older pre-OBD II "speed density" way of measuring the amount of air being drawn in.  If this solves your problem you've definately got a faulty MAF.