multible misfire problem please help!!!!!!!!!!!

Hey everyone….long time reader first time poster.

I am having a similar problem to most of the post I have read here about my 99 blazer idling rough. It almost stalls completely at stoplights. Today the motor shut off while driving. I pulled over and the coil wire had melted into the coil.

Let me start by telling you what I have done so far.


new spark plugs (properly gaped)
new plug wires
new coil
new cap and rotor
cleaned the EGR Valve (mine is electric, diff. from some I have seen on this board)
Checked O2 sensors (dirty, black carbon – I cleaned up a little and burned them clean with a torch)
Removed the Cat (also dirty with carbon but I didn’t notice anything loose or rattling)
took to AutoZone to have it checked. Code 300 multiple misfires (this is after everything listed above)

Here are the details on my blazer

99 4.3 V6
102,000 miles

at around 80,000 the motor was rebuilt after the water pump went out and did some damage to the motor – not sure on the details but after it was said and done it was around $2,000

at about 95,000 I ran the car through high water (just came out of nowhere). The car stalled out and would not turn over. The next day I changed the oil, fuel filter and TPS (was not shifting properly).

Since the water damage the car was running fine. Only recently (past 3,000 miles) have I been having idling problems.

I drive for a living and can put 100 miles on my car in a day no problem. I do take care of it, change the oil every 3,000 and maintain the small stuff. I am at a loss here; it has never given me this much trouble.

You may have one or two or more problems.
Only problem with the P300 missfire code it does not tell which cylinders are missing.
Was that the only code?
If idle is bad there should be other codes.
You need to get it on a good engine capable scanner and see which cylinder or cylinders are missing and read out Past and history and present miss fires.
And check camshaft retard setting and fuel trim readings.

Can you feel a engine miss?
Is the check engine light flashing on the road?
What brand of spark plugs did you put in it?

I would also confirm good fuel pressure.

Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

The first place I went to said #2 was misfiring. The second place said multiple. Yes, that was the only codes I got.

1.If you mean feel the engine miss by running rough then yes. Other than that I’m not sure.

2. The engine light is solid no flashing anytime.

3. They were Autolite plugs.

I wouldn’t be able to tell you the fuel pressure; I do not have a meter. I will say this you can smell gas if you are driving behind me on the road but there is no gas smell under the hood. It is also hard to start.

I hope you guys can help me find a solution, I need to get back on the road and make some $.

The first place I went to said #2 was misfiring. The second place said multiple. Yes, that was the only codes I got.

1.If you mean feel the engine miss by running rough then yes. Other than that I’m not sure.

2. The engine light is solid no flashing anytime.

3. They were Autolite plugs.

I wouldn’t be able to tell you the fuel pressure; I do not have a meter. I will say this you can smell gas if you are driving behind me on the road but there is no gas smell under the hood. It is also hard to start.

I hope you guys can help me find a solution, I need to get back on the road and make some $.

First thing pitch the auto light plugs in the trash can and get the AC Delco the book calls for. On a Gm 4.3 you need AC delco plugs.
Make sure it is getting good hot blue spark to all plugs.
Even new wires can be bad.
If no 2 cylinder miss showed up on one scanner check that cylinder real close.
Hold brake and put a pull on engine and pull plug wire on that cylinder and check for miss.

Did you figure out what melted the coil wire?


Rent or borrow or buy a fuel pressure gauge and confirm good fuel pressure.

(Hold brake and put a pull on engine and pull plug wire on that cylinder and check for miss.)

can you explain this?

I have no idea what melted the coil, I was hoping someone here could tel me.

Thanks

In addition to what MT-2500 suggested, what distributor cap and rotor were installed? Some aftermarket caps have problems with breakdown of the epoxy insulation between the bussing.

Since the truck ran through water, was the air filter replaced?

(Hold brake and put a pull on engine and pull plug wire on that cylinder and check for miss.)

can you explain this?

I have no idea what melted the coil, I was hoping someone here could tel me.

Thanks

Automatic transmission?
Warning.
If you have a pace maker do not try it.The ign voltage is real high voltage.:nono:
If automatic have someone help you put it in drive and hold there foot on the brake.
The pull the plug wire off of plug and listen for good hot spark when it is a 1/2 in to a 1 in off.
Then pull it all of the way off and see if engine will miss or watch for RPM drop.
If so that cylinder has a miss.
Good idea to do it on all cylinders.
Just get it rest and put in park between cylinder test.

On the coil wire we can not help if we can not see it.
Can you post a picture.
Or tell how it is burnt.
Burnt or melted or just came apart?

Ok, here is the latest...

I took the car to a shop by my house and asked if they could check my fuel pressure. A guy ran out right then and checked it for free and this is what he said.

The pressure was low until the car cranked for about 3 or 4 sec then got a reading of 55. Once we turned the car off the pressure was gone and dropped all the way to around 15 or so. He recommended a new Fuel Pressure Regulator. What do you think?

I bought a new Fuel Pressure Regulator. The car is cooling down now and I will let you know if the problem is fixed.

Ok, here is the latest...

I took the car to a shop by my house and asked if they could check my fuel pressure. A guy ran out right then and checked it for free and this is what he said.

The pressure was low until the car cranked for about 3 or 4 sec then got a reading of 55. Once we turned the car off the pressure was gone and dropped all the way to around 15 or so. He recommended a new Fuel Pressure Regulator. What do you think?

I bought a new Fuel Pressure Regulator. The car is cooling down now and I will let you know if the problem is fixed.

Proper testing will tell.
Go back to my post no 2.
It tells the proper fuel pressure test.
The line pinch off test will tell you if it is fuel reg or fuel pump.

Always make sure the fuel pump has full fuel pressure to.

I have finished installing the Fuel Pressure Regulator and cleaned up the throttle body. The car runs better (more responsive) but still idles rough and misses at low rpms.

I will have to take it back up to the shop and have the pressure tested again.

Does anyone have the spark plug wiring diagram for our 4.3. I am starting to think I crossed a wire.

Cap top has the # cyl stamped on it and the drivers side front to rear is 1-3-5 and pass side 2-4-6. The drivers side out of cap is not in 1-3-5 order but 3-1-5 out to plugs - look at cap #s. It will backfire if you cross those two.

Cap top has the # cyl stamped on it and the drivers side front to rear is 1-3-5 and pass side 2-4-6. The drivers side out of cap is not in 1-3-5 order but 3-1-5 out to plugs - look at cap #s. It will backfire if you cross those two.

thanks, wires are correct. Any other ideas?