Anyone know the temperature of the stock thermostat on a 94 explorer 4.0L? I have a pinging problem and am wondering if going to a cooler thermostat might help the engine run a little cooler and help with the pinging problem. Does this sound like a good idea or a complete waste of time?

 

Forcing the engine to run cooler may mask a pinging problem, because the computer will artificially enrichen the mixture. If the engine doesn't come up to the temperature it expects (192-195 F), then it constantly runs in "warm-up mode" instead of the most efficient mode.
That said, there are several possible fixed for pinging on the 4.0 OHV. It seems to be a common problem.
1) tighten the lower intake manifold bolts. they seem to work loose over time. The first time I had problems with my engine pinging this fixed it. Now I periodically tighten them as a matter of preventive maintenance.
2) Clean the MAF. This worked the second time I had a pinging problem. A dirty MAF sends an incorrect signal to the computer about the amount of air coming in, causing the computer to run the engine lean. Along similar lines, a vacuum or intake leak downstream from the MAF will allow unmetered air into the intake, causing a lean condition and ping.
3) Decarboning the cylinders. A little seafoam, water, or your favorite method for removing carbon from the cylinders. This is also a common fix.
4) Dirty injectors that don't allow enough fuel in, thus causing the engine to run lean.
5) A bad ECT can also cause a ping, by sending a high temperautre reading to the computer, causing it to run the engine lean.
That should be a good start. Let us know how it goes.

 

THanks for all the suggestions. I have already tried several of these, and some have helped more than others.

1. Tighten the lower intake manifold bolts. I think I did this. Are there upper intake manifold bolts? I tightened the bolts that hold the intake to the block. Are these the bolts that you are referring to?
2. Cleaning the MAF. I have done this, and it didn't help.
3. Decarbon the cylinders. I did this last week, and this is what I had the most luck with. It didn't eliminate the ping, but it helped a lot.
4. dirty injectors. Is there a way to clean them without taking off the intake? Should I just dump a detergent fuel additive into the gas tank?
5. I'll look into this.

I did use my old, old voltmeter to pull codes from the computer, and if I was reading them correctly, the code was 33. The hayes manual says that this is the egr valve not opening because of insufficient flow. The egr valve and egr pressure sensor were both just replaced. I know the code is new, because I cleared the codes and then disconnected the battery for good measure for about 15 minutes. What else could be causing this error code?
Thanks.