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******* SPACESTATION
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Discussion Starter · #1 ·
About every week or so my CEL will come on, I read it and it has 3 codes:
0300 random multiple misfires
0302 cyl 2 misfire
0307 cyl 7 misfire

The truck doesn't miss when it's runing, the light only comes on after I start it.
It's got brand new 8.5mm MSD wires, so even though induction shouldn't be possible with those wires, I insulated every other wire with convolute (flex conduit).

My question is, what would cause it to read a misfire when I crank it up? I spin the starter long enough. It only throws the code every week or so, and never when it's running. Only right after startup.

Any ideas?
The truck runs great, but this is getting very frustrating! :banghead:
 

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******* Yankee
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What are the condition of the plugs? Check cap on the top of the plug (I don't know the proper term). Did it unscrew a little causing a bad connection?
Maybe a crack in the cap letting in moisture? When you first fire it up it gives you a misfire code but then the moisture evaporates and it runs fine. Hope you figure it out. Lets us know what you find.
 

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Chizzle1,

I've got the exact same problem. I've had the truck for almost 4 years now and every once in a while at startup it will throw the same codes. I've replaced cap, rotor, wires, plug and coil, still throws the code every now and then.

Temperature and weather don't seem to matter either. I have to bump the engine three times before it will crank when it's cold (the engine, not the weather). If it's warm it will fire as soon as I bump it. But if I let it sit for more than 15 or 20 minutes, I have to bump it 2 or times again.

Hope someone can help you with this so maybe I can learn something from it.

Good luck.
 

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******* SPACESTATION
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Discussion Starter · #4 ·
It hasn't thrown the code since I installed the convolute...maybe MSD wires aren't as insulated as advertised.
At any rate, if the convolute fixed the problem I will get some more and insulate all the wires, right now I only insulated every other one.
 

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Derelict
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392 Posts
TSB 18-48-98 is all about ignition system cross fire and how to reroute the wires to fix the problem.
 

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******* SPACESTATION
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Discussion Starter · #7 ·
how would changing plugs affect induction?
the same plugs have been in it for a while, this only started after I upgraded coil & reconnected IAC.
I will be driving it to work all next week, so if it doesn't misfire again, I will chalk it up to induction since I have installed the convolute over every other plug wire.
I don't think I should have to insulate with MSD 8.5mm wires, but oh well.
 

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I have just had my magnum in the shop for code 3 engine misfire. It has supposedly turned out to be a bad PCM----that tells the engine what to do do. The valve and sparks are good, but the computer bad. My CEL would come on and try to reset itself (3 good starts) but fail eventually. I waiting....good luck.
 

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******* SPACESTATION
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Discussion Starter · #9 ·
honestly, if that's all that is wrong with it, I wouldn't pay the $$$ or $$$$ to get it replaced.
Is the truck actually misfiring, or does the CEL just come on for no reason?
Mine was only setting the CEL on start up and would not misfire while running.
Since installing the convolute, no CEL so I'm guessing i was still having a problem with induction for some reason.
 

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******* SPACESTATION
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Discussion Starter · #10 ·
Chizzle1,

I've got the exact same problem. I've had the truck for almost 4 years now and every once in a while at startup it will throw the same codes. I've replaced cap, rotor, wires, plug and coil, still throws the code every now and then.

Temperature and weather don't seem to matter either. I have to bump the engine three times before it will crank when it's cold (the engine, not the weather). If it's warm it will fire as soon as I bump it. But if I let it sit for more than 15 or 20 minutes, I have to bump it 2 or times again.

Hope someone can help you with this so maybe I can learn something from it.

Good luck.
just so I understand what you are stating: you have to crank it three times before it will fire and run?
Have you tried cycling the key from 'off' to 'on' 3 times? If that helps it could be a fuel pump problem, as cycling the key will actuate the fuel pump.
Try that and see what happens.
 

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chizzle1 said:
just so I understand what you are stating: you have to crank it three times before it will fire and run?
Have you tried cycling the key from 'off' to 'on' 3 times? If that helps it could be a fuel pump problem, as cycling the key will actuate the fuel pump.
Try that and see what happens.

Yes, I bump it three times to start it. It will start if I just keep cranking it, but I don't like doing that to the starter.

I put a vacuum/pressure gauge on the fuel line once and cycled the key three times. Each time I cycled the key the pressure would go up. But on the first cycle the pressure was low. I can't exactly remember the numbers right now. I hoped that tuning the PCM with the Hypertech would help the problem, but sorry to say it didn't.

I got a feeling I'm going to be replacing a fuel pump before spring rolls around again.
 

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******* SPACESTATION
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Discussion Starter · #12 ·
I put a vacuum/pressure gauge on the fuel line once and cycled the key three times. Each time I cycled the key the pressure would go up. But on the first cycle the pressure was low. I can't exactly remember the numbers right now. I hoped that tuning the PCM with the Hypertech would help the problem, but sorry to say it didn't.

I got a feeling I'm going to be replacing a fuel pump before spring rolls around again
didn't you just answer your own question?
If the pressure is low on the first time the key is cycled on, try cycling it a couple more times prior to start up.
You will need to replace the pump soon, but this should keep you from having to engage the starter more than once.

by the way: the hypertech does nothing to your fuel pressure. It's a 'piggy back' system (like Superchipcs, Jet, etc) that changes what the PCM sees, not what it's programmed to do.
 

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chizzle1 said:
didn't you just answer your own question?
If the pressure is low on the first time the key is cycled on, try cycling it a couple more times prior to start up.
You will need to replace the pump soon, but this should keep you from having to engage the starter more than once.

by the way: the hypertech does nothing to your fuel pressure. It's a 'piggy back' system (like Superchipcs, Jet, etc) that changes what the PCM sees, not what it's programmed to do.

Even though the pressure increases with each key cycle, I still have to bump the ignition a couple of times or just let it keep on cranking before it will start.

The thoughts on the hypertech were more about timing adjustment than fuel pressure. With the additions of new 3923 autolites, MSD coil, MSD 8.5 wires and the ProFlow 1002 I was hoping that it would improve the hard start problem.

But as you pointed out, I'm going to be replacing the pump before too long.

Thanks for the info Chizzle1.
 
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