94 Chevy 350. Back fire through TBI

Discussion in 'GM Powertrain' started by James4012, Feb 23, 2013.

  1. James4012

    James4012 Member

    Alt is brand new. Back in January when I started fiddling with it again It wouldn't drive faster than 20 before it was cutting in and out. I noticed the battery light on at that time. The alt was dead and the battery couldn't cope with the demands of the fuel pump under acceleration. All the sensors this truck has are all new. The ignition module under the dizzy was the first to be changed. I ment it on the first post lol. Everything but the crank and pistons are all brand new. Cam all the way up to the bow tie on the air filter all thread. Everything has been replaced. I'm pulling the dizzy this weekend though. Going to see what happens when I throw the spare from my 305 in it. Ain't got nothing to loose. Worst case, pull the motor and sell it. T_T it's now more valuable then the entire truck is.
  2. geo1

    geo1 Member 100 Posts

    got to be external,right?besides dizzy swap,check power supply at dizzy,thinking fusible link?try wiggle test,and at starter too,any wire with expanded insul,i.e. either side of links,low volts to dizzy make for many diff. situations,keep me informed
  3. James4012

    James4012 Member

    I was talking with a couple of the mechanics as were I work and each of them said Dizzy. I went ahead and installed the 305 dizzy, hooked it back up and ran it down the road. Ran fine, but sadly still back fires. I mean it's not like it causes any problems with the way it runs. Honestly even when I'm driving along at 70MPH, it's doing it every 3 seconds without a single variance in time between back fires, despite that it has no lag in forward momentum. Doesn't stop moving, hesitate or in anyway impede the trucks acceleration. It's just annoying and embarrassing. Oddly, doesn't do it at all under hard acceleration. Go balls to the wall in 4th gear at 60-75MPH and it doesn't do nothing. Throw it in 5th. *pop pop* I'll take a look at the wiring this weekend, though I'm sure all of that is fine :/ *sigh* I love chevys to death. I'd rather push a chevy then drive a ford. But that love ain't mutual it seems XD Also on the replacement dizzy I went ahead and used it's rotor, cap and ingnition module just to check if the originals I had were faulty. No change their either.
  4. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Had a 87 cavalier that would missfire under a steady light load and clear up under moderate to heavy accelleration. Turned out to be a leaking EGR valve.
  5. James4012

    James4012 Member

    This one only does it under casual driving, up to moderate acceleration *depending upon which gear it's in* Doesn't ever under heavy. I replaced the vacuum advance on it last week or so as a last resort if that's what the EGR is, round black thing with a vacuum hose on it. Lol I usually don't know the name of every part, but I usually know what it does at least. The vacuum line on it is new as well. Now maybe the sensor it goes to is bad? I was looking at it here yesterday comparing it to another I have. It's not the one with a filter like this http://contentinfo.autozone.com/znetcs/product-info/en/US/wl2/EVS3/image/4/ It's different. Don't know if that bothers anything.
  6. James4012

    James4012 Member

    Finally resolved the problem. Wasn't the motor at all. Turned out it was the transfer case. The chain inside was busted and rattling and catching on stuff. Changed it out, haven't had a problem yet so far. Truck has no muffler and the I cut a hole in what's left of the pipe in front of the converter, so it's hard to tell where sounds are coming from over the roaring of the motor. Running alright so far (better stay that way to, the motor is all brand new by now lol)

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