mypoorLS1

iTrader: (4)

My car developed a misfire. Changed plugs and wires. No.1 plug was very black. Misfire was still there. Long story short, did compression test, checked rockers, vacuum leak, fuel pressure, swapped no.1 and no.3 coils then injectors and no.1 plug still turns black right away. Misfire still there. Any ideas? BTW, according to the laser thermometer, that header pipe is 90 -100 degrees cooler than the rest.

LilJayV10

iTrader: (39)

Sounds like you have checked everything the easiest/best way. I'm wondering if the wire that goes to the #1 injector has a short to ground. That's the only other thing I can think of at the moment.

mypoorLS1

iTrader: (4)

I thought the same thing. I cleaned the connector at the coil. There is spark to no.1. Would anyone happen to know which wire in the plug goes to ground?

mlmedina26

Is the spark plug wet? How was the residual fuel pressure once the engine was shut off?

LilJayV10

iTrader: (39)

What year is it? I will check.

mypoorLS1

iTrader: (4)

Its a 98 formula

mypoorLS1

iTrader: (4)

Plug was dry. Plenty of pressure after shutdown. It really seemed like it took forever to bleed it off. Probably half cup of fuel came out before pressure was gone.

LilJayV10

iTrader: (39)

mypoorLS1

iTrader: (4)

Those would be perfect but it looks like schematic for injector, not the coil. But I may not be looking at it right. I'm on my phone

LilJayV10

iTrader: (39)

It is for the injector. I misunderstood which one you wanted. I will get you the other one.

To see if #1 coil is firing hook up an extra spark plug and lay it on the engine somewhere and start it. If you have an inline spark tester that works well too.

LilJayV10

iTrader: (39)

mypoorLS1

iTrader: (4)

Thanks a lot. This will help out a ton. I have to ateast diagnose the problem tomorrow. I'm on my back to Nashville on Tuesday

FAD2BLK93

Just curious, what did the compression test show on each cylinder?

mypoorLS1

iTrader: (4)

200psi. All 8 cylinders were within 6psi

mlmedina26

I didn't see your post about no spark when I posted.

mlmedina26

From the diagram they all share the same ground so look for an open on the ground side cause its the easiest thing to do and then check for a signal from the PCM to the coil. Maybe check resistance values on both ground and power. Hope you can figure it out before you have to leave.

mypoorLS1

iTrader: (4)

It is getting spark. It just seemed weak. Used a screwdriver to check that. I feel as if all my bases are covered, but still have the problem. Guess turbomach is gonna have to bring his diagnostic tool from work.

mlmedina26

Have you tried swapping injectors around just to make sure you don't have a clogged injector?

mypoorLS1

iTrader: (4)

Yes I did.

03turbomach1

iTrader: (2)

Found it...Broken valve spring. Why do it seem like all aftermarket head manufacturer use **** valve springs anymore, GM seem to have the same trouble, with some of there springs too.