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04-25-2012
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#1 |
 Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,480
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Back fire at start
Just put headers and exhaust on the car. Now when I start the car in the morning, it backfires? kinda'. Injectors leaking fuel into cylinders? I've only had the car for a year and I don't know if they've ever been changed.
TIA Steve 
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04-25-2012
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#2 |
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Join Date: Mar 2009
Location: Orlando, FL
Posts: 1,828
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Re: Back fire at start
I was experiencing backfires on a consistent basis when I had a vacuum leak.
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2004 Z06/Z16 LeMans Commemorative Edition 1991 ZR-1 #302 White/Gray (sold) 1991 ZR-1 #1147 Red/Saddle (sold) |
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04-25-2012
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#3 |
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Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,480
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Re: Back fire at start
It only does it when I first turn the key, before it really fires up. Seems to be running fine. Altough the idel has been high, and fluctuating. Maybe a vacuum leak, or just 'cause it's breathing better.
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04-25-2012
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#4 |
 
Join Date: Jul 2007
Location: Bartlett, IL
Posts: 7,169
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Re: Back fire at start
leak in the exhaust at one of the pipe joints will do it too
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1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978 |
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04-25-2012
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#5 |
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Join Date: Mar 2009
Location: Orlando, FL
Posts: 1,828
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Re: Back fire at start
High fluctuating idle is another common sign of vacuum leak. How is your cruise control and HVAC working (do all the different vent positions function properly)?
__________________
2004 Z06/Z16 LeMans Commemorative Edition 1991 ZR-1 #302 White/Gray (sold) 1991 ZR-1 #1147 Red/Saddle (sold) |
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04-25-2012
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#6 |
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Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,480
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Re: Back fire at start
haven't used the cruise lately. HVAC seems to be ok, but I'll pay closer attention. It does this before the engine even fires up. Like one of the cylinders had some fuel sitting in it.
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04-25-2012
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#7 |
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Join Date: Mar 2009
Location: Orlando, FL
Posts: 1,828
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Re: Back fire at start
yes, mine was doing the same thing when I had a vacuum leak at the junction of the check valve and the line that supplies the HVAC and cruise systems with their vacuum.
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2004 Z06/Z16 LeMans Commemorative Edition 1991 ZR-1 #302 White/Gray (sold) 1991 ZR-1 #1147 Red/Saddle (sold) |
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04-25-2012
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#8 |
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Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,480
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Re: Back fire at start
Sounds like I better start looking for a vacuum leak. I would have thought a vacuum leak would only be a problem after the car was running.
Key on, engine not running- vacuum pump cycled at 1 min, 45 sec's. It only ran for about 2 seconds. |
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04-25-2012
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#9 |
 
Join Date: Jan 2009
Location: Portland Oregon metro area (Washington side)
Posts: 3,207
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Re: Back fire at start
I get a backfire every time I release the key too early after a start.
Solution: I keep the key turned a little longer.
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Scott  Vett owner since 1979._It's about the car and the people |
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04-25-2012
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#10 |
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Join Date: Jun 2010
Location: back in lone pine
Posts: 591
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Re: Back fire at start
might ck and see if the hose connected to the sensor at the back of the plenum is tight , it gets oil and heat soaked and can leak .
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