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Random Multiple Misfire, Running out of Solutions

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Old 07-23-2011, 04:16 PM   #1
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Random Multiple Misfire, Running out of Solutions

My 01 Blazer was idling really rough, throwing the random misfire code for a couple weeks, I changed all the spark plugs, wires, and cap and rotor, no difference. Then my truck started blowing steam out from the hood, turns out my intake gasket blew. The weird thing is that after it blew, my rough idle and misfire problem went away. Next day I go and get new gaskets, a new thermostat, and a new spider injector. Everything gets installed and now my idle and misfire problems are back, but now only after the car heats up. If I let it sit overnight it starts up faster than ever before and runs fine until it heats up. Then if I go to start it maybe an hour after it's been turned off, it has to crank for about 6 or 7 seconds before it starts. Does anyone have any idea what the problem could be?
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Old 07-23-2011, 06:15 PM   #2
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Re: Random Multiple Misfire, Running out of Solutions

She runs good cold then runs like poo when warm... Sounds like the o2 sensors need to be swapped for new ones... My z28 did the very same
Old 07-26-2011, 10:18 AM   #3
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Re: Random Multiple Misfire, Running out of Solutions

ignition control module is also prone to failure once the motor heats up. causing random misfires.

most parts places can test it, and the coil, but make sure it is good and hot when you take it in. i always put it on the dash, with defrost on high heat on the way to the store.
Old 07-26-2011, 06:41 PM   #4
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Re: Random Multiple Misfire, Running out of Solutions

could be stopped up exhaust (cat)
bad coil
bad icm
could also be a bad fuel pump, check fuel pressure when warm. it could be failing,
what about fuel filter?
any vacuum leaks?
Old 07-27-2011, 03:26 AM   #5
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Re: Random Multiple Misfire, Running out of Solutions

I already replaced the coil, I cleaned the EGR valve out as best I could with brake cleaner, I'm gonna get some carb cleaner and a wire brush and do it again, but then misfire code has gone away. The idle is still pretty rough, and it still starts hard when it's hot. What are the chances the brand new spider injector is defective? Fuel filter and pressure check is my next step, I'm not sure of any easy way check if my cat is clogged, though I've definitely considered that as possible cause. I'm gonna try a new crank sensor tomorrow, and I'll likely pick up the O2 sensors as well, since those have brought up codes in the past. As far as I can tell there aren't any vacuum leaks.
Old 07-29-2011, 03:25 PM   #6
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Re: Random Multiple Misfire, Running out of Solutions

any updates? I am having a random misfire, but my truck is running good other then low idle
Old 07-29-2011, 09:27 PM   #7
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Re: Random Multiple Misfire, Running out of Solutions

just had the same problem with me 98 blazer ran great until warmed up did the basic cap rotor plugs wires and didnt fix it finally took it to the shop and it ended up being coil coil module and then the computer had to re learn the new parts they said runs great now
Old 08-03-2011, 01:17 PM   #8
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Re: Random Multiple Misfire, Running out of Solutions

Sounds like you need to do a full diagnosis...

Don't Throw any more parts at it until you can get some one to help you figure it out. (I made that mistake on my wife's truck thought it needed a tune up... 800$ later I find out that the intake valves are burned on multiple cylinders.)

- I'd wait on The crank sensor and the o2 sensors Unless you know they are bad.

To check the cat just unbolt the exhaust and ensure that the core isn't broken or has melted craters burned into the face (engine side) (you will need new gaskets to put it back on or the flanges will leak)

-you can Test for vacuum leaks with a "smoke test" most competent repair shops can do this test.

-I might would go for a leakdown test and a head gasket test and rule those out as well.

I might would suck up my pride and take it to a shop that has the Snap-on or Tech-2 scan tools and can do a full diagnosis on it. there are still a few shops out there that diagnose and not just sling parts
Old 08-03-2011, 02:19 PM   #9
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Re: Random Multiple Misfire, Running out of Solutions

first thing.

if the gasket were lekaing internally into the cylinders than you o2 are toast due to the coolant. coolant has silicone in it and silicone will destroy o2's. I have seen this alot on BMW's and GM where headgaskets were blown and then the car/truck will run liek crap once at running temp. no codes will be set.

remove both pre-cat o2. crank eng. if it runs better than you have a stopped up exhaust. if not htan you exhaust is fine. removing them relieves the back pressure.

then check fuel pressure. if you dont have 60 psi than it will run poorly.

yes do the free stuff first b4 you go and fling more parts at it.
Old 08-03-2011, 03:24 PM   #10
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Re: Random Multiple Misfire, Running out of Solutions

And if I have a stopped up exhaust then I'll have to change the cat?
Old 08-03-2011, 03:27 PM   #11
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Re: Random Multiple Misfire, Running out of Solutions

Quote: Originally Posted by S15vortecpwr
if the gasket were lekaing internally into the cylinders than you o2 are toast due to the coolant. coolant has silicone in it and silicone will destroy o2's. I have seen this alot on BMW's and GM where headgaskets were blown and then the car/truck will run liek crap once at running temp. no codes will be set.
I did not know this... I guess that's why that some gasket makers say O2 sensor safe and some aren't.
Old 08-05-2011, 01:42 PM   #12
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Re: Random Multiple Misfire, Running out of Solutions

I've had a car once apon a time, lol, that when cold would run like a champ, and once it warmed up, it would start to run like crap. And once it got to operating temp and sometimes past, it would be running like complete POS. Barely make it to 5 if you were lucky. Hope this isn't happening to you. Mine was a plugged cat. One die I was driving it home from work, and all the sudden it got loud a crap(blew out donut gaskets). Ran like a champ all the time after that, but the damage internally was already done. That pressures gotta go somewhere!
Old 08-05-2011, 04:09 PM   #13
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Re: Random Multiple Misfire, Running out of Solutions

I have a friend who just replace the cat on his 96 Jimmy, but his Jimmy is beyond repair, so he's gonna sell me the whole thing for $500 and I'll take what I need off of it.
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