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#1
05-02-2009, 10:35 AM
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Mystery missfire
Hello, I am brand new to the forum. I have a 1994 Blazer, 93K miles, with a 350. It has a mysterios dead miss at idle. Will idle than miss, idle than miss. I have changed cap, rotor, plugs, wires, and O-2. No help. Ignition module was changed 2-months ago; new exhaust and cat. Tried to clean the TBI on the intake while running, no help. Checked timing; verified at 0 BTDC. Does ping under load, even with running 91 oct gas. Hooked up scanner; only had EST timing code and cleared that.
Any suggestions would be wonderful on what to do next. 
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#2
05-02-2009, 12:48 PM
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Re: Mystery missfire
¿Have you tried watching the ignition coil with the engine running in the dark? ¿Have you tested fuel pressure while this was happening?
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#3
05-02-2009, 12:57 PM
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Re: Mystery missfire
No actually I haven't checked the coil; I'll get one today and change it out. Thought about it before I posted. Will let you know. I haven't taken a fuel pressure reading either, but have suspected intermittent failure. Never shot a code for it though. Will reply again when I replace the coil.
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#4
05-02-2009, 01:46 PM
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Re: Mystery missfire
Spray carb cleaner around the base of throttle body and see if the RPM's change. I have seen several of these gaskets gone bad and created a vacuum leak.
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#7
05-10-2009, 03:15 PM
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Re: Mystery missfire
Quick update; missfire returned. Checked tightness of TBI before replacing gasket. Retightened 2.5 turns; also changed fuel filter (had black crap in filter; dark black dirt). I'll try that and see what happens...if that doesn't do it I'll drop the tank and change the fuel pump.
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#8
05-10-2009, 04:05 PM
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Re: Mystery missfire
If the throttle body was that loose, Change the $3.00 ? gasket and pick up fuel pressure tester before you drop the tank. No need to throw $$$ at it without testing first.
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#9
05-10-2009, 06:39 PM
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Re: Mystery missfire
Yes, I hear you....just typing away. I'll change the gasket this next weekend. I have one already. Just thought tighting it would suffice for now. I have to drive it this week for work so I'll see what transpires tonight through Thursday. I'll keep you posted.
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#10
05-29-2009, 07:23 AM
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Re: Mystery missfire
Changed TBI gasket and put some Lucas in the gas tank. Still idles a little rough but I will drive it to see if it clears out. The throttle has loosened up dramatically and acceleration is better. I don't think a fuel pump is needed at this time. Thanks for the help.
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