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Hesitation, backfire, possible miss? Help.

  • Thread starter Thread starter Fett
  • Start date Start date Jul 29, 2008

Fett

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Nov 2, 2004
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Jul 29, 2008
#1
  • Jul 29, 2008
  • #1
Ok, this started a few weeks ago....sort of. I started having a backfire issue randomly. I would really notice it during the first few minutes of driving when the car was cold, if I was accelerating between 2500 and 3200rpms I would hear a popping backfire through the exhaust...a distinct popping, almost sounded like a physical POP. The car would hesitate/buck/lose power at the same time, I would normally let off the gas coast for a second, and get back on it and it would go away. After warming up, it wouldn't happen again.

Today, out of the blue, the car started running like total crap. Drove to work normally, started it up for lunch and the hesitation exhaust popping was very much present. Under ANY accel, it would buck and hesitate...and generally feel like it didn't have all it's normal power.

After work I started working on spark. I changed the plugs, the old ones seemed slightly worn, but none of them were cracked, gaped to far/close, or fouled that I could see. Nothing changed after the plug change. So then I disconnected my MSD, again no difference. I also datalogged (Tweecer R/T) to watch my TP sensor to see if there were any flat spots. Worked fine, at idle it reads 1.03, at WOT it reads 4.7....and during full, slow sweep....there were no jumps or gaps in voltage.

I did datalog my WB and my stock O2s, as well as load and timing back when I was originally feeling the backfire, but even when the car backfired I didn't see anything off in my datalog that gave me any idea of the problem, my A/F looked ok.

I am at a loss, and obviously am thinking a thousand different things. From an injector loading up a cylinder, to TFI, to dizzy.....even bad gas or filter. The thing that is throwing me is the fact that, even though I was getting the random backfire, todays problem came out of the blue. It wasn't an issue where it slowly started running worse...it just all of a sudden started running like crap. So whatever was causing the backfire all of a sudden went south....quick.

I don't expect anybody to have a single answer...I'm just looking for ideas.

Thank you.
 

Fett

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#2
  • Jul 29, 2008
  • #2
Forgot to add, my fuel pressure never faltered during any of this.

So the things I have ruled out are plugs, bad MSD, and fuel pump/pressure.
 

MY 85 GT

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Mar 7, 2008
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Jul 29, 2008
#3
  • Jul 29, 2008
  • #3
Wow sounds excatlly what my car is doing right now...... Myabe its what im going to change out my Magnetic pick-up in the Dizzy? Actually im changing my whole dist....my car is 23 yrs old ...Thought it mught be a good idea...
 

Fett

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  • Jul 29, 2008
  • #4
Yea, I'm kind of pointing at that myself. I figure, I must be loading up with fuel somehow, either bad injector....or something isn't right with ignition.

I figure my next step will be to try TFI module....cheap enough and easy enough to change. I HATE throwing parts at my car....but given the issue, I can't think of any other way to solve it.
 

jrichker

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  • Jul 29, 2008
  • #5
What codes did you get? Is the smog pump system still intact and functional?
 

Fett

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Jul 30, 2008
#6
  • Jul 30, 2008
  • #6
jrichker said:
What codes did you get? Is the smog pump system still intact and functional?
Click to expand...

That's a problem because I get no codes because of my Tweecer, I have smog, tad/tab, egr, and evp all disabled through the Tweecer.

The only way to get codes would be to disconnect the Tweecer and wait for codes to show up. I might have to do that just to see what, if any, misfire codes I get.
 
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