Engine Backfire under acceleration

Discussion in '1994 - 1995 Specific Tech' started by 94mustangcobra, Jan 1, 2013.


  1. 94mustangcobra

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    Alright, i've tried everything I can think of before coming on here looking for advice. The car drives fine when you drive easily but when you lean on it, once it hits around 3k it (regardless of gear) it starts breaking up and backfiring. I can hear both fuel pumps on when I start (255 in tank, and 50 gph inline), I've fixed one vacuum leak and replaced a suspect vacuum line to the fuel canistor. Cleaned the mass air sensor and filter, replaced all plugs, plug wires, cap, rotor, fuel filter. Codes from computer are only 511 (it has a chip), 159 (80 mm Pro-M mass air meter). I've pulled the valve covers and looked for broken valve springs and found nothing, leakdown tests show little leakage coming from dipstick, compression tests cylinders are all within 5% of eachother. Only thing I can think is the distributor (MSD pro billet, been on since 2004) has some corrosion on it under the rotor, where the stator (or hall effect sensor......whatever it is) passes. I was thinking of getting a temperature gun or whatever it's called to shoot the headers and see if one is cooler than the rest. I'm lost....any thoughts.....
     
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  2. 11B_stang94

    11B_stang94 New Member

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    ive had the same problem before in a 96 i had. it was the harness to the timing on the front of them motor. only thing i could tell you with the 5.0 being so different is to check all harness connections. i had to replace the harness and its a ****. could be from an clogged injector also, you just have to keep troubleshooting until you find it
     
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  3. toyman

    SN Certified Technician

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    Is the car boosted? The PIP and coil problems quite often do not show up in the DTC's.
     
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  4. 94mustangcobra

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    nah...it's a N/A 347....i forgot to mention i just replaced the coil as well and it didn't solve it.....the reason for the duel fuel pumps is because i'm running a dry shot of nitrous, it was recommended to me by the tuner at Anderson Motorsports. I'm running 30 lb injectors with duel fuel pumps.
     
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  5. 94mustangcobra

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    *update* cleared the codes by disco'ing the battery overnight. At first i checked the codes KOEO at the codes were 511 and 111. All good....cleaned up the distro and went for a disappointing drive....now it's breaking up with any throttle......won't rev in the driveway without backfiring.......ran the codes again and now with KOEO i got: 511 and in the memory it came up with 212 (ignition module circuit failure/SPOUT circuit grounded). After that i did the KOER and got codes 311 and 314 AIR system inoperative during KOER (banks number 1 & 2 with dual heated oxygen sensors).

    Ok now i'm reading the 311 and 314 are for the smog system which is completely removed and i thought tuned around. Smog system is removed from the intake and plugged. Thermactor plugs are in the heads and have been there since 2007.
     
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  6. toyman

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    Unplug the MAF to see if it runs any differently. I would suspect a code if it were a MAF issue but there are always exceptions.
     
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  7. Ryleighsdad

    Ryleighsdad Member

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    I was gonna say coil, but I see you swapped that. Sorry man.
     
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  8. 94mustangcobra

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    yeah i think i've narrowed it down to either the TFI or the PIP in the distributor, still gonna have to shoot some wires to see if anything weird happens
     
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