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Jeremy Phipps
Jeremy Phipps, Chevy Technician
Category: Chevy
Satisfied Customers: 111
Experience:  12+ years automotive diagnostic and repair experience, Chevrolet/GMC Truck fanatic. =D
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1995 chevy blazer: diagnostic..4 misfire..rotor..only 200 miles driven

Customer Question

I have a 1995 chevy blazer with a 4.3 litre vortec cmfi system I ran diagnostic on it and got po304 cylinder number 4 misfire, new plugs wires cap and rotor also new crank sensor. Checked compression it is at 120 lbs in that cylinder as well as the others one was 130. The plug is dry black carbon fowled after only 200 miles driven. Spider injection working fine as far as i can tell aany suggestions i replaced the plugs with a platinum bosch crossmatch to ac delco plug. Help no idea at this point.
Submitted: 8 years ago.
Category: Chevy
Expert:  Jeremy Phipps replied 8 years ago.
Hey Carrie.
The Bosch Platinum plugs have very different characteristics from the OEM ACDelco plugs, and quite often will cause a misfire on Chevrolet engines. I actually had the ceramic part of a Bosch platinum plug blow completely out of the engine on my old 2.8 litre S10 Blazer. No one seems to know the details as to why they don't work very well, but I've come to avoid them at all costs, especially on GM V6's. The aftermarket "crossfire" distributor caps are also very prone to problems, so you want to get the cap directly from Chevrolet whenever you do an ignition tuneup.

The fact that the spark plug is dry and dark is a good sign that you (probably) don't have a problem with the injector, so you should be safe there.

Are you having any driveability problems with the truck? Do you feel the misfire at idle, or when you accelerate?