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Random Misfires - Runs Rough (Intermitently)

  • Thread starter Thread starter extremetrek
  • Start date Start date May 21, 2008
E

extremetrek

New Member
Mar 30, 2005
106
0
0
Prescott, AZ (66.6%) Central Point, OR (33.4%)
May 21, 2008
#1
  • May 21, 2008
  • #1
Greetings,

Ever so long ago I got great help with my personal 5.0 so i'm hoping you guys can come through just as well on my roommate 04 v6. Im really unfamiliar with this setup, heck the first time I popped the hood I was astounded to find the dizzy missing...go figure, so please bear with me.

The vehicle recently has been running rough and misfiring. Its happend on two seperate occasions the latest the worst. In between the car runs perfectly normal. This last time we came to a light and the car began sputtering and shaking, gas pedal to the floor resulted in absolutely no effect on the engine whatsoever. Shut the car off, restarted it, still ran pretty rough but with enough time it started to move and finally shifted out of 1st (Auto) and cleared up a bit. It seemed so long as it was about 2.5k it was ok. Then heading back home, it started again, slowing down for a light got to about 20mph and suddenly no engine response via the gas pedal, massive shaking and perhaps a backfire (though I couldn't confirm this) again shut it off, restarted and it was ok. The common thread here was that the first time it was 90+ deg in Phoenix and the second it was 90+ deg here in Prescott so that may be a clue.

In all of this the CEL was flashing, so she decided to run it to the clueless ones at Autozone to scan it (I only have an OBD-I reader). The guy who scanned the car told her he hated his job and so on, and reported that there was a generic (all-cylinder) misfire code in memory. He only did the engine off test no engine running diagnostics were performed. Today I pulled the plugs and everything looks perfectly normal the wires are fine, I checked other things I know like the MAF and everything checks out fine. My thinking is that there is either a fuel flow issue (FPR? FP? Other?) or somethings up with the PCM. We're leaving out of state and her mother will be needing the car while we are away so we have about 1.5 weeks before we have to break down and go to the stealership. Any advice would be greatly appreciated!
 

cjones

Founding Member
Jul 20, 2002
1,561
0
37
Avondale, AZ
May 21, 2008
#2
  • May 21, 2008
  • #2
how long til it will restart??

does it only do it when she's low on fuel??

what's the fuel pressure when it happens??

she should take it to another autozone or store to have all the codes run (KOEO, KOER). the first question on the diagnostics routine is "are any other codes present?".
 

Skymarshal

Member
Nov 5, 2004
572
0
16
Dallas
May 21, 2008
#3
  • May 21, 2008
  • #3
Replace the plugs. I had a similar (but not as severe) misfire, and eventually tracked it down to a cracked plug that would occasionally spark through the porcelain and ground out. It's a cheap thing to try.

It might also be a camshaft position sensor. If it's providing bad data, the engine will lose its timing and valvetrain synchronization.
 
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