How can you tell if you have the wrong type of spark plugs? The guy I bought my 1994 Z28 from said he put NGK Spark Plugs in the car, but I'm afraid that he put in the hot burning plugs instead of the cold. My car misses once the car gets up to operating temperature. I am well aware that this problem could be cause by a wide variety of things, which is why I am not ruling anything out, other than the alternator because I checked it already.

Also, does anyone have spark plugs that they recommend for my Z?

 

im using ngk tr55ix iridium plugs

 

The brand of plug is not that important, although in a particular car, some work better than others. What is really important is the heat range, tip type, and reach, which is indicated by the numbering on the plug. Get a NGK plug chart and see if the right plug was installed. I have found that on an unmolested engine the best performing plugs are the ones that the factory initially installed, but they may no longer be available.
As for the misfire when hot, hot plugs do not ususally cause misfires, but then can cause preignition and pinging. Most likely there is a bad plug wire, or some part of the ignition system that fails when hot, or there is a sensor problem which shows up when in closed loop. Force the engine to stay in open loop by unplugging the MAF wires. If the misfire stops then you need to scan for a bad sensor or a new MAF.

 

My MAF was backwards up until I noticed it last week. I switched it around but would that have anything to do with it?

 

I believe that you can still get the Delco platinum plugs. I have those in my car and they were installed about 1.5 years ago.

 

Quote: I'm afraid that he put in the hot burning plugs instead of the cold

You may not be understanding what the difference is between a hot plug and a cold plug. It has nothing to do with the spark size or temp, the combustion temp, etc.

A hot plug is one in which the center electrode or "tip" is more exposed inside the plug shell. This means that there's less contact area for heat to be conducted away from the center electrode into the plug shell and consequently it stays hotter. OTOH a "cold" plug is one in which there's a large contact area betwen the center electrode and the shell so a lot more heat is conducted from the tip to the shell and the center electrode is colder.

The danger of using a hot plug where it isn't called for is that the tip can act like a glow plug and cause preignition (detonation). Hot plugs are very handy on an older engine that burns a little oil and tends to foul plugs though.

Pull one of you plugs and check the numbers on it. There are NGK online application guides that will tell you what you have.