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vortec 4.3 V6 misfire

fordsucks!

fordsucks!

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Vortec 4.3 in my 2005 Astro van. Just started a real nasty misfire. At first it was a P0300 random misfire, after a few miles it has transformed into a P0305 (#5 cyl misfire)


I have opened up the dog house and looked at the distrib, plug wire etc, don't see anything out of the ordinary, will start digging into it tomorrow but does anyone have any input?

I've had these Vans before where the fuel injection spider causes issues, I'm hoping this is not the case as zero space for wrenching!
 
fordsucks! said:
I wish. Traditional six point distributor that spins off of the crank.
Click to expand...
I would start with wires and plugs, if not then it's the distributor cap and rotor.
I just had a 97 5.7 that was doing a p0300 then it quit.
After checking fuel and spark I popped up the cap and the rotor was sitting on top.
One screw loosened up and fell and the other sheared off.
 
Cap and rotor is a pretty common issue to run into on any 4.3. Stick with Delco parts as I've seen the aftermarket stuff not last very long.

One item of concern is the distributor itself. They have a plastic housing with bushings for the shaft to spin against. The bushings wear out and causes the shaft to wobble. That makes the spark irratic but would not show itself as a cylinder specific misfire. It would be random, p0300 type misfire where it jumps around.
 
Thanks all. I did cap and rotor today, zero change. Still running like a tractor with immediate p0305.

We'll try spark plug and a wire next, but if it's beyond that then I want to assume fuel injection spider. I have $105 diagnostic appointment set 4 days from now.
 
ZooMad75 said:
Cap and rotor is a pretty common issue to run into on any 4.3. Stick with Delco parts as I've seen the aftermarket stuff not last very long.

One item of concern is the distributor itself. They have a plastic housing with bushings for the shaft to spin against. The bushings wear out and causes the shaft to wobble. That makes the spark irratic but would not show itself as a cylinder specific misfire. It would be random, p0300 type misfire where it jumps around.
Click to expand...



This is good info... might be worth pulling the cap again and see if the shaft is sloppy loose. Might even pull the distributor out to check it.
 
4.3 can have a bunch of issues...

Plastic distributor housing is important to check.

Don't forget intake gaskets. There are updated versions (felpro) that are available at basically any parts store. The failure we these tends to be coolant passages though.

If you wanna tear into it and just replace some stuff, I did intake gaskets and spider injection through Rock Auto for just over a couple hundred bucks.

I have seen a bunch of 4.3 heads crack, but if I remember correctly it was earlier versions. Again, if I remember correctly, it would crack between seats and then kill the valves. It has been so long since I was in the machine shop that I could be totally off base here...
 
Seen quite a few 4.3's at my friends shop come in with carboned up EGR passages that may hold open the EGR valve enough to cause misfires at idle..he takes the valve off and reams out the passages with a drill bit and a rifle type wire brush..
He's replaced many "spiders" and distributors on them too..also some injectors--if one injector has an intermittent short it causes the others to "misfire" too..mouse chewed wiring has been found on several trucks he worked on also..
 
SpeedlabDan said:
Plug OK? Plug wires go bad too start with the basics
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Bingo! #5 plug was not okay. I mean it was a cheap autolite brand, totally black and I didn't see anything physically wrong with it, but I put a new AC Delco in and boom problem is gone!!!!

Someone clearly has done a full ignition tune-up on this van before, the plug wires, plugs and distributor are all cheap replacements.

Thank you all so very much! Just save me a ton, 110 would have been the diagnostic fee tomorrow


20210221_150750.jpg
 
It only takes one dead soldier to ruin the whole platoon when it comes to spark plugs....congrats on a lucky cheap fix!..

My friend has had several GM trucks come in skipping ,or run much worse after a fresh tune up with the customer supplied platinum spark plugs..(especially Bosch ones for some reason)--often tossing in a set of "regular" AC plugs cured all the poor running issues..
 
Platinum plug caused skips have been around about as long as there have been platinum plugs. Way back on Compuserve, in the automotive section, most of us had a pre-written answer when someone posted a problem with misfires after a tuneup.
Basically it went along the lines of: If your vehicle did not come from the factory with platinum plugs, and you put platinum plugs, that is the problem.

When platinum started coming on strong, there were lots of ads about its long life. Given the high voltage applied to spark plugs, it just never seemed likely to me that the difference in resistance could cause that much trouble.
But something sure did.
If you swapped out regular plugs for platinum, you were almost guaranteed a misfire problem. Non-platinum engines' ignition systems just could not handle them.
The resistance of platinum at any given size is almost 10 times greater than copper, but at these tiny distances, the differences are also tiny.
But something sure makes a difference.
Of course, platinum is a famous catalyst, so it could be affecting the burn, but if it was, then it should be doing it for all engines. Plus the amount of it that the air/fuel mix is exposed to is so small its effect should be negligible.
 
All the vortec's with distributors have cap and rotor issues, the wear out in 10 or 12k miles. The spider injection system used to be the main problem, but once replaced with updated unit will last a good long while.
I mostly dealt with v8 not to many v6, but the 4.3 is just a sawed off 5.7.
 
Fordum said:
Platinum plug caused skips have been around about as long as there have been platinum plugs. Way back on Compuserve, in the automotive section, most of us had a pre-written answer when someone posted a problem with misfires after a tuneup.
Click to expand...

Yes the problem plugs are Autolite platinum, repair plugs AC Delco iridium
 
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