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Need help asap. Can't solve misfiring problem

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Old Dec 29, 2016 | 07:41 PM
  #1  
Mattkovitch's Avatar
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From: Boyertown, Pennsylvania
Car: Firebird
Engine: 305 tbi
Transmission: 700r4
Need help asap. Can't solve misfiring problem

I was driving it all day (1991 firebird 305 TBI) stopped at a friends house to pick up a few parts he was selling to me. And went to leave and it wouldn't stay running unless I kept giving it gas. It died once trying to get it out of his driveway. I got it home (5 minutes down the road) foot to the floor just to keep it moving. I tried it later and it would start up and misfire a bunch, they seemed like random misfires not certain cylinders. It would stay running on its own at idle. I replaced the spark plugs (the ones in it were AC delco and looked to be in okay shape) with AC delco plugs, the parts store only had pro start wires (I wanted AC Delco or MSD, but I need my car running so I bought them) replaced all plugs and wires, set the gap correctly on all the plugs, no wires are in the wrong place everything was correct. I started it and now it sounds like it's misfiring even more, and won't stay running longer than 4 or 5 seconds. I replaced the ICM next (don't remember what brand, it was the more expensive one at the parts store) and the problem persists. It sounded like it was running better, maybe it's just in my head, but again won't stay running sounds like only a couple cylinders are firing. What do I do next? Clogged cat? Bad distributor? I don't wanna keep buying parts that aren't gonna fix it. All the while all the new parts I ordered a few days before this happened are getting here and I just wanna take it out and drive it with all the new stuff before it really starts snowing here in PA.
(it is getting fuel, you smell nothing but raw unburnt gas coming from the tail pipes everytime I try to start it)

Last edited by Mattkovitch; Dec 29, 2016 at 07:45 PM.
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Old Dec 29, 2016 | 08:52 PM
  #2  
G.Penrod's Avatar
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From: Clinton, UT
Car: 86 Iroc Z-28
Engine: 5.0 TPI
Transmission: Automatic
Re: Need help asap. Can't solve misfiring problem

Not sure if it's exactly the same but my TPI was having the same type of issues. After I did a tune up it was still happening. I took out the ECM and found that the PROM wasn't fully seated. After I reseated it the car ran perfectly. Might be a long shot but could be worth giving it a look at.
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Old Dec 29, 2016 | 11:21 PM
  #3  
Mattkovitch's Avatar
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From: Boyertown, Pennsylvania
Car: Firebird
Engine: 305 tbi
Transmission: 700r4
Re: Need help asap. Can't solve misfiring problem

Where is the ecm on these cars?
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Old Dec 30, 2016 | 09:17 AM
  #4  
navy02ws6's Avatar
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From: Atlanta
Car: '02 T/A WS6, '91 T/A, '91 Camaro RS
Engine: LS1, LB9, L03
Transmission: T56, 700R4, 700R4
Axle/Gears: 4.10 10 bolt, 2.73 10 bolts
Re: Need help asap. Can't solve misfiring problem

IIRC, it's behind the lower dash panel on the passenger's side.
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Old Dec 30, 2016 | 09:27 AM
  #5  
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naf
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From: Lexington, SC
Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: Need help asap. Can't solve misfiring problem

replacing the distributor cap and rotor is a routine maintenance type of thing. do that if the age and/or condition of your existing set is at all questionable.

these pieces/parts don't usually just up and die for no reason. ignition components will usually begin to fail when heat soaked and may work fine again after cooling down.

i would next check your fuel pressure and look for a good spray pattern from both injectors.
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