1996 GMC YUKON MISFIRE

[GOOFYLSX]

HEY GUYS IM NEW TO THIS GROUP I WOULD TO GET SOME OPINION ABOUT A PROBLEM IM HAVING HEAR ME OUT I HAVE A 1996 GMC YUKON 2 DOOR IM HAVING PROBLEM WITH A MISFIRE CYLINDER P0304 I CHANGE THE SPIDER INJECTORS THE CAP N ROTOR SPARK PLUGS N SPARK WIRES N IGNITION COIL N IGNITION CONTROL MODULE

I DID GET WHITE SMOG COMING FROM THE TAIL PIPE WHEN IT COLD STAR

IM THINKING ABOUT REPLACE THE HEADS OR REBUILD THE MOTOR

LMK

 

[89Suburban]

Cracked head? Loosing any coolant?

 

[B-train]

Um....before bringing out the "jump to conclusions mat" I'd do some basic checks.
1. Coolant level - checked cold and after several drives. Same or not?
2. Does the white smoke go away quickly (like normal cold exhaust), or is it white and billowing for a bit - very dense.
3. Does the misfire go away relatively soon after startup when white smoke disappears?
4. Does it have a hitch in its giddiup when cranking (ie: a noticeable slow/high spot)?
5. Do you have a good scan tool to check injector cut-out and see if one isn't functioning?
6. Are all electrical connections seated and tight? (Spark plug wires, etc). Did you hear/feel the click when installed.

Basic, but could be effective before motor disassembly

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

Also, please lose the ALL CAPS.

 

[Eman85]

Let's put the wallet away and start diagnosing. You changed a lot of parts, was there any reason for changing or just guessing? You retrieved a code so I'm guessing you have a way of reading a code or did you go to the parts store and have them read it? Did you find anything wrong with any of the parts you changed? How many miles on the truck and how has it been taken care of? Did you do a compression test? Start there and let us know what you find.
Don't know the size of your wallet or how deep you want to go. You're talking past the hundreds when you start talking a rebuild and into the thousands.

 

[exp500]

White smoke is fuel. check fuel pressure at several rpm ranges while driving if possible (6 foot hose under wiper blade), as well as key on eng off.
Unplug cold start sensor for a test start.
Next check O ring at fuel inlet to injector. Next check fuel pressure regulator.
Could possibly be timing also.
Report back here all your findings.

 

[east302]

Adding to the above, when were the intake gaskets last replaced?

 

[West 1]

I helped a friend fix his 99 5.7L with a #5 misifre. Random, would come and go. Ended up being carbon build up on the valves making them sticky. Sometimes they worked perfect with no mis fires and sometimes it was a dead miss.

A leak down on that cylidner will show if it is an issue with exh valve or intake valve and rule it out quick.
A compression test would let you know if the cylinder is intact.

If you continue to run it with a dead cylinder you will be buying new Cats soon, they don’t put up with excess fuel for long.

 

[GMCChevy]

White smoke on cold start is pretty normal. When you changed the plugs did you check what they looked like? That would have been a good starting point. Or if you still have them do they all look the same?