94Z28rag

ok, well my car has been running on what seems to be 7 cyl for almost 3 weeks now. its a pretty bad skip/misfire and a decent loss of power. no SES light.

i changed the coil from MSD Blaster back to stock, nothing.
i changed the wires (all Taylor 8mm before and after), nothing.

BUT, last night i decided to pull all the plugs, which aren't very old, and my #5 cyl plug is BLACK. the electrode and ceramic part, basically everything that's inside the block is black. doesn't seem very oily, but could be a leak somewhere.

another thing i tried: i am 90% sure its on the driver's side because i can hear the ticking on that side, and listening to each injector through a screwdriver(as a stethiscope) i found that the #3 injector is not as loud of a ticking. so i started to pull off fuel injector connectors one at a time to see if when i pulled one off there would be no change in the engine sound...

when i did this, i found that when i pulled the #3 cyl injector plug, the car ran exactly the same. no change in anything. i tried it again, the engine sound changed...

i continued pulling, and the exact same thing happed when i did #5 cyl. so its almost like i maybe have a clogged injector or two???

the opti is a year and two weeks old, all new plugs, wires, and coil. no SES light ever. still missing. an oil leak has started and is dripping on the opti, but it doesn't seem like that would cause only this slight problem, i'd think it would be more severe.

last, i'm having the car scoped by my mechanic so we can try our best to diagnose this problem and then i can fix it myself. i have a heated garage and a lift and air tools so its not a problem to do myself.

thanks for any replies, this was a long one. :nonod:

133,000 miles on the car and motor, if that helps.

94 NO TOP Z

I would swap the plug and plug wire on that #5 (just use the old plug wire if you still have them). If it is black it sounds like it isn't firing.

slopokrodrigez

If the plugs look black and velvety, that indicates a rich condition. Once fouled enough, they won't fire the cylinder. That could be the reason the cylinders aren't running. So when you remove the injector plug, the cylinder doesn't change. Being they (I think you said #3 and 5) are fouled, then that indicates there is too much fuel getting to them. Therefore the injectors aren't clogged shut but could be clogged open. This begs the first question, how often have you replaced the fuel filter?

You want to check the fuel pressure AFTER the car is shut down to see if it stays up at the level it was when it was running. If the injectors are clogged OPEN the pressure will bleed down. Another condition a clogged open injector can cause is longer than normal cranking. It can also, although more rare, cause what is called crankcase dilution. Fuel in the oil. Check the smell of the dipstick. Change it if you do.

One quick thing to look at is the vac line on the pressure regulator. See if it's wet, if so the FPR is leaking fuel into the intake and causing a rich condition. BUT this usually effects the right bank cylinders more than anything.

Also, if the engine has been running real rich for a long time, you may have damaged the cat convertor and/or O2's. Also it is a bad idea to run long with a cylinder that is putting in fuel and not firing since it will wash the cylinder of the oil film and could suffer galling. Sometimes refered to as SOUPING.

Let us know what you find.