[93GrandRegal]

I have a misfire in my 1993 Regal Series I. The misfire is noticeable at start up but gets worse as the engine warms to operating temp or when the a/c is turned on. It has been this way since I got it.

What I've done:

-I have checked the coils both cold and warm and they are all within range between 5 and 6 ohms.
-Sparkplugs look fine and wires are new.
-checked the fuel injectors they are all working.
-No oil in coolant or Coolant in oil.
-I noticed the radiator level is never all the way full when I check but no external leaks after pressure test

I'm thinking a possible cracked head with water in the cylinder causing a miss and crack opening wider at op temp, Maybe bad intake valves. Any input would be great.

 

[gtx500hp]

DTC code should pull up which cylinder misfiring on. Very possible leaking intake gasket. Happened to our series 1 95 Transport 3800. Corroded intake from factory causing #5 cylinder misfire. Many years ago.

If intake gaskets have not been done, you are way overdue. I replaced them on our van again about 8 months ago. They were really shot. No dexcool in this engine now, but sure ate them up bad.

You may try spraying carb cleaner around intake to look for a leak. Rougher idle too? Obviously just a start of possibilities.

 

[93GrandRegal]

Thanks for the reply. This car was manufactured pre-dexcool but since i'm not the original owner I dont know it ever had it in the system. It just had water when I got it. Also there is no check engine light just a miss.

 

[gtx500hp]

OBD 1 IS nowhere near as picky as OBD 2. You still could use a scanner. I bought an Actron scanner. It really helped me diagnose our van. A reall wiring nightmare of an issue back then. You really need to find out which cylinder is missing. You may then be able to swap injectors or wires, etc. to find out if it is some thing easier than an air leak...best of luck!

 

[93GrandRegal]

*Update*
Ended up checking the spark to all the wires with a spark tester and got nothing at 35,000 volts on cylinder 4. Switched the coil with the 3-6 coil and the problem moved to cylinder 6 so looks like a bad coil even though the ohms were in spec. I will replace it and give another update. Still don't know what's causing the small coolant loss though. Thanks again.