Chevy engine question

[Bill]

98 Suburban 1500, 350 ci.

335k only internal repairs done was a new intake manifold gasket at around 100k I think.

In the past it's thrown P304 and P300 codes, I've replaced the plugs and it was ok. Started running rough, P300/P304 this time thing this time, dumb but I put in Champions. Still rough.

Now it turns over, but will not start. I figured I'd pull all the right side plugs and put in AC Delco and the 2 and 4 are black and dirty with around 100 miles, and 2 had oil on it.

I'm afraid the Gray Ghost may be a goner- something nasty. What would explain not starting and the bad plugs I pulled out?

Leaving for Montana tomorrow to see out son for Thanksgiving so ill be checking TBH when I can but won't be able to try anything for a week until we get back.

[firemedic2105]

Bad coils causing plugs to foul? Did you test the new plugs for spark before you put them in?

[AddisonOil]

I had the same problem with my 99. Changed the coil and is running like a champ!

[SAVIOUR68]

Check fuel pressure as well as the pressure regulator, those older style regulators have a internal diagpram which ruptures and fuel is sucked directly into the intake manifold causing misfires as well as a no start. Regulator is the gold colored thing on the left center picture mounted to the CPI . As you can see that the fuel will flow from the nipple on the regulator and into cyl 2/4 intake runners explaining your issue. Good luck.

http://www.theautoshop.net/VortecMPFI/PC060019.JPG

[Artos]

Good luck Bill.

Wow that's as lot of miles...my 99 only has 180k. That's pretty cool your s has gone so far. My understanding is the 99 was the last year of the iconic 350.

It runs lie a top & drivetrain is solid...it's just all the other little stuff that is wearing me thin. I would love to dump some money into it & turn it into another ranch vehicle some day. The 82 J10 we have is great but boy it gets old on hot / dusty days. An enclosed vehicle with AC//heat is golden every now and then.

[knapper]

Plugs can tell you a lot of info
Black and oily ?
With those kinda miles, I would bet it would be valve seals leaking or rings

These engines did not have seperate coils for each cylinders

[Bill]

Chevy engine question

Here's the 4 plus, front to back left to right. There's only 100-200 miles on these plus.

[Ol Thumper]

Not to be negative but regardless of the problems this time your motor is nearing it's end, it's not real common to get that milage out of one before something major let's go but it appears you have had one heck of a motor over the years. If it were me I would manually check the fire on each cylinder and then run a compression check on each cylinder since you have that many miles just to rule out the obvious. If you have firing and decent compression on each cylinder the next item to check is the fuel pressure. It's simply a process of elimination but with your milage a few other factors come In to play but checking fire, compression and then fuel you can skip through the major items pretty quick.

I have rebuilt over 2 dozen of these motors and everything in between, their about as simple as they come. Once you check the basics report back and we can go from their,

[Bucksaw]

Sounds like its time for a new GM Performance 383HT crate motor.

[mavrick]

One on the left is not firing. Check the coil.

[Wits_End]

I have a 99 Tahoe, it only made it 175K before falling on its face. Rebuilt tranny, transfer case, rebuilt and stroked to 383 and diff gears in front and back all within 5K miles. Runs and tows like a beast now.

Common problems with 5.7L vortec and misfires, many have already been stated:
Spider injectors stuck open causing tons of fuel to be dumped into cylinders. Typically see other symptom such as loss of mpg, changing from 16mpg or so to 10mpg or so and loss of power.
Distributor cap on these get corroded quickly, within a year. They are not perfectly sealed and vent is horrible. Causes loss of power and eventually random misfires, p300.
Have always heard to only use ACdelco plugs. It wont cause it to not start, but just saying.
Check fuel pressure. Should be 60psi minimum with key on, engine off. These engines are very sensitive to this. Would either be regulator or pump.
Timing - If you can scan it, check crankshaft timing with engine running, should be +/-2deg at 2K rpm. With that many miles, your distributor may be worn out and either skipped a tooth or something of that nature. Being off one tooth will prevent it from starting.
Bad gas

Just need air, fuel, and spark....at the correct time.

[Bill]

Chevy engine question

Thanks.
I'm all packed to leave for Montana to spend Thanksgiving with our son. Plan is to hunt mornings (ducks a mile east, public land elk 3 miles west!), work on his house afternoons and then sit back with a couple beers in front of the fireplace evenings.

I'll check the distributor and rotor when I get home. Is the ignition coil built into the cap on this Chevy engine?

[Wits_End]

No. Ignition module is on passenger side of the intake 3/4 of the way back. Just distributor, cap and rotor in thst assembly.

[Wits_End]

Trip sounds like one of my dreams. Good luck!

[Bill]

Great trip, lots of mornings out hunting elk, white tail does and waterfowl. Other than the cow elk that ran down a hill into my son's Dodge RAM rear door, nothing died but a great time together

The Suburban's problems:
- needed new rotor and cap
- thermostat was leaking and not losing so engine ran cold, fuel mixture was too rich as a result.

$400 later, it ran well driving home.