The way how those platinum +4 work is probably a very good design for a motor which has the spark plug located in the centre of the cylinder head (4 valves, hemi style).
How ever if you drop them in a 2V 4.6 L modular (spark plugs located on the side of the combustion chamber), they don’t work properly:
Out of those 4 prongs of the spark plug, at least two get way to hot, probably due to their location in the combustion chamber. Those two prongs were snow white which means that the temperature that has been created on the spark plug was so hot, that it burnt the carbon deposits 100%. This causes “hot spots” which can create pre ignition -> pinging.
How ever the other two prongs were brown / grey coloured, which means incomplete combustion or not enough temperature.
I do not recommend you to use those Platinum +4 plugs in your car. They can only create troubles but no real power gain.
Sorry this is not a mustang put I thought it might be of some use.
It was time to change my sparkplugs (almost 90K).I decided to try bosch +4 plug's # R3 385 or part # 4458. After installing the new plugs the engine (454 vortec) the engine was running rough. I had no time to check the problem had to go on a planned trip of 600 miles total.The truck ran terrible, when I returned home I changed the plugs back to a new set of AC 41-932's. The engine ran like new. All of the Bosch plugs were dark and oily.I called Bosch and told my story to a service agent (Joe) .He told me to stick to original plugs in that engine and to call a techie for a refund (lost receipt).I asked Joe to get back to me as to what the problem was . After sending plugs to him I recieved them back with a letter.
The sparkplugs submitted for inspection have been evaluated All of the spark plugs are gasoline and oil fouled. The submitted spark plugs are the correct plug for the application. No defects were found.
This situation would not be considered a warrantable condition and therefore Bosch can not provide any compensation assistance in this matter.Tha spark plugs submitted for evanuation are being returned to you.
We apologize for any inconvenience this situation may have caused you.
Automotive and Diesel Products
So does anyone have an idea why the old AC plugs ran fine, the Bosch plugs ran bad and the new AC plugs ran fine ?
This is the answer I wanted from them mainly because I had such high hopes for these plugs.+4 I want to know why there plugs did not work. I know the Bosch plugs were fouled, but I know they didn't have many miles on them and they made the truck run rough at an idle, gave me poor gas milage, and less power. They ran bad, right from the start.
Electricity follows the path of least resistance. If the resistance to all four posts was exactly (and I do mean EXACTLY) the same, you would get 4 sparks. But they would be weak sparks, because the available spark energy would be divided by 4.
At best, you'de get two sparks, both weaker than required. What happens to any engine when spark energy is reduced by 50%? It pings, runs bad, and gets bad gas mileage.
There's no magic in spark plugs. Not yet, anyway. A $1.50 Autolite will make the same power as a $10 double platinum plug. It just won't last as long. I use standard autolites in everything, and I never have ignition problems. Even in my 550hp small block.
I've seen problems with bosh in general. My friend had a '91 Escort GT and had a set of bosh platnums in there and the ground fell off in the combustion chamber. Anyways the +4 plugs are a waste of money for anyone no matter the engine. There will only be one spark that comes off the electrode at one time, it doesnt make sense to get the +2 or +4 waste of money and the fact that its just a sales pitch just to get peoples money for a bogus product. Unless there is four electrodes and and four wires that go to it followed by a x4 coil pack thats the only instance you will get four sparks at one time. well thats my two cents.
A forum community dedicated to Ford Mustang owners and enthusiasts. Come join the discussion about performance, builds, modifications, reviews, engine swaps, classifieds, troubleshooting, maintenance, and more!