Report: How I "cured" Knocking On 00 Vulcan

Originally posted by apolinaras@May 5 2004, 11:19 PM
I suggest very much against t-stat swap. ECU will think that engine has not completely warmed up and will dump extra fuel into the mixture, so you will run rich, your MPG will SUCK big time.
Believe me, I have been through this hell for past year or so, service advisors at Northridge Ford here in Chicago know my voice when I call (that is how much I have tortured them). It is Atlanta plant idiots who failed to build headers right, they are not being cooled properly. The TSB I had done on my car to set the computer straight did not do $hit but waste my half day.
Change the sparks, flush the coolant, pop-in the Water Wetter. Cheaper, quicker!

BTW, call the dealer and check if you have an outstanding brake switch safety recall, I just found out mine did (and I follow these things very closely).

Click to expand...

You're referring to the engine running in a constant open loop. Engines will do this if the computer determines that the coolant isn't hot enough; it'll run blindly, which means dumping fuel into the engine to prevent detonation (because rich is better than lean.)

Closed loop occurs at a temperature below 180, though; I haven't found any solid numbers, but the places I have found reference 130 (I bet it's a bit higher than that.) Putting a lower temp thermostat in may be able to decrease the temp of the engine to a point where pinging will cease; if this is true, actual MPG will raise, because detonation is actually the engine working against itself. The engine should also feel more powerful, although the increase may be negligable.

In the least, if a lower temperature thermostat reduces temperatures too much, a CEL will appear, saying "Insufficient Coolant Temperature for Close Loop" or something along those lines. Our Explorer gets that in the winter, because the thermostat won't close all the way. If the light comes on, put the old temp thermostat in, simple.

More than likely, it's a timing issue. Either the gasoline is of too low an octane rating or too low of a grade or some condition in the engine is creating excessive heat, or a combination of the two.

Have a compresion test done to measure your compresion ratio. 9:1 Ratio will call for 91 octane or higher. 8:1 is normal for 87 octane. 10:1 is dangerous for regular vehicles, unless you are programmed to run on 100 octane fuel on a regular basis.

The spark is igniting too far away from the spark plug or the spark is too weak. If your timing is over advanced, then the spark plug is igniting too early. You may need a new knock sensor or have the computer reflashed or try a better spark plug.

Other general reasons for preignition, knock & pinging, self-ignition:
-too-lean fuel/air mixture (not enough gas for the air present)
-incorrect valve timing
-engine cooling system inadequacy
-faulty exhaust gas recirculation (EGR) valve
-high intake-air temperature
-driving in too high a gear
-excessive carbon deposits
-poor combustion chamber design/shape

Try a different fuel source. Some companies don’t put key additives in their fuel mixture to help against knocking. Domestic vehicles need all the additives available to run without denotation problems. Sunoco Gas, Union 76, Texeco all use Oxidation inhibitors. This prevent gasoline from developing gums that clog up the works. When gasoline reacts with oxygen in the air, peroxides or gums can form and degrade the fuel’s antiknock quality and attack plastic parts. Soluble gum can lead to engine deposits, and insoluble gums can plug fuel filters. Inhibiting oxidation is particularly important with fuel-injected engines, which may be subject to higher temperature and oxygen-exposure stress.

I know that bulk gasoline companies (generic, store brand name fuel ei, Costco, SAMS) and Arco do not use Oxidation Inhibitors or Corrosion additives in their fuel mixtures. This can adversely effect the performance of our vehicles. Most foreign cars are unaffected by this, because their programming and emissions are different. So stay away from cheap bargin fuels if you want your car to last.