Serious spark knock!!

[hockeytown]

Need some help with my 92 Explorer! I have just replaced my MAF for the second time (still under warranty) and my TPS sensor and I am still getting real bad spark knock. Is there another sensor that I'm missing? The truck has 142,500 miles on it and it was running great. At 130,000 I had the check engine light come on accompanied with a breif surge that occured prior to the check engine light coming on. I pulled the codes and found out the MAF was bad and replaced it. Everything was running great then one day last week the check engine light came on again along with the surge. Like a dummy before I pulled the codes I replaced the TPS sensor and that did not help. I pulled the codes and discovered that it was the MAF again and replaced it. Now the check engine light is not coming on but I am still getting severe spark knock when you give it gas. How do I get rid of the spark knock??

 

[MrShorty]

One thought. Remember that codes point to circuits/systems rather than components. In other words, an MAF code does not necessarily mean a bad MAF. It means that the signal the computer saw was different enough from what the computer expected it to be that it threw a code. As an example of what I'm saying, if you take the air intake tube off and run the engine, you will get an MAF code no matter how functional the MAF is, because no air is flowing through the MAF.
One question: Is your MAF code a KOEO code, a KOER code, or a continuous memory code? If you don't know, then let's find out, because that will help us in diagnosing your MAF problem.
I used the example of disconnecting the intake tube on purpose. One common cause of ping is any vacuum leak or air intake leak downstream of the MAF. This causes the engine to run lean which ultimately causes it to ping. One interesting vacuum leak that is common to the 4.0 OHV is a lower intake gasket leak. Over time, the bolts that hold the lower intake on loosen, which allows a leak. Usually tightening the bolts is enough, but occasionally the gasket needs replaced.