Car is hesitating/w a backfire while building boost or just into boost

Turbobuick#1035

New Member
Jun 4, 2018
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Ok guys see if you can think of something as I’m outta options here. Car starts fine,idles fine and runs fine at normal driving. Once I start to get on it and boost starts, it hesitates and even a backfire will occur. Here’s everything I’ve swapped out with good known working parts to try this process of illumination. I’ve changed a the coil pack and module,I have a MAF translator so I put a new MAF on there nothing.I even went back to a stock MAF, i’ve swapped out the O2 sensor, I tried a new map sensor, fuel pressure is fine fuel holds as boost is building it’s not dropping off, The battery is fine the alternator is fine, I change the computer I change the chip that did not fix the problem. The cam sensor cap was changed. Changed the wires, put new plugs. TPS is good and set correctly. The problem is still occurring. What else could it be? Any suggestions?
 

blackazz

Not a Gn
Sep 1, 2008
1,258
212
63
Grand nashville
I'm having the same problem as you. Does it come an go as if you hit a switch?.some days I come out an it drives like a dream then well driving it switches up on me.then bucking surging an back firing like a machine gun.

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Turbobuick#1035

New Member
Jun 4, 2018
21
1
3
40
I'm having the same problem as you. Does it come an go as if you hit a switch?.some days I come out an it drives like a dream then well driving it switches up on me.then bucking surging an back firing like a machine gun.

Sent from my SM-G930T using Tapatalk
Mine does not come and go..it happens every time I get on it..can’t figure it out yet
 

Rick the pool guy

Active Member
Feb 7, 2017
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Massachusetts
Ran into this a couple of years ago I did the same thing for parts .took a good module off a running car same problem. So after chasing the problem for hours .We decided to go with a brand new module out of the box and coil and it fixed the problem.
Don't know why or how but it worked
Put the parts back on the running car and it didn't have the problem that the other car had
 
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berserker6

Assistant to the regional manager
Oct 1, 2009
1,234
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jersey
I once had a problem where in any gear the second I would get in to boost the car would shut off for a split second and then clear up. Idled fine. Drove fine except for that specific issue. It was the wire coming off the alternator and over to the battery. It would short out on drivers side exhaust under acceleration.
 
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lhbarrett

Member
Jul 25, 2003
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Check if the air intake pipes are sealed correctly/tight. What are you using for air intake? Could be un-metered air entering behind the Mass Air meter. Is your plug gap correct? Boost pressure? If above 12 lbs turn it down.
 

NY Twin Turbo

All the good stuff.....Times 2.
Dec 10, 2014
2,622
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Westchester NY
In my limited experience, a bad coil pack will cause it to sputter backfire and miss under boost, and a bad module will cause it not to run at all.........maybe intermittently, but not at all.

But a bad plug wire or 2 will do the same as a bad coil pack. Don't trust that they look 'just fine' or they are 'brand new'. Look very closely at them. Twist them around your finger and look for cracks and splits. Especially near the boots. Build boost in the pitch-black dark as someone looks around under the hood for lightning. As soon as you cross over from vacuum to boost, that spark will jump out of that wire at the first spot it can find easier than the plug.
 

ScottHeidinger

Active Member
May 2, 2015
684
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northeast Florida
Have you checked your voltage. My alternator was crapping out on me and it started running as you describe your issue. It didn’t light up the idiot light but with my AC and lights on it would break up under boost and I noticed my fuel pressure gauge was reading lower than usual. I didn’t have a voltage gauge at the time so I assumed it was my fuel pump. Then my radar detector started powering off saying low voltage when I would sit in traffic. Car started fine every time I drove it. The only other time it would break up as you describe my intercooler coupling wasn’t all the way tight and under boost it would leak. It didn’t blow off completely and looked fine but leaked under boost. Have you checked all your intercooler hoses and clamps?
Someone else already stated that the fuel pressure should rise 1:1 with boost. I have a electrical fuel pressure gauge on the pillar to make sure. They aren’t cheap but I feel much better knowing my fuel system is working properly.
HTH


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Turbobuick#1035

New Member
Jun 4, 2018
21
1
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Do you have a Scanmaster ?? We need more info , KR , fuel pressure rising with boost , & what plugs .
Have you checked your voltage. My alternator was crapping out on me and it started running as you describe your issue. It didn’t light up the idiot light but with my AC and lights on it would break up under boost and I noticed my fuel pressure gauge was reading lower than usual. I didn’t have a voltage gauge at the time so I assumed it was my fuel pump. Then my radar detector started powering off saying low voltage when I would sit in traffic. Car started fine every time I drove it. The only other time it would break up as you describe my intercooler coupling wasn’t all the way tight and under boost it would leak. It didn’t blow off completely and looked fine but leaked under boost. Have you checked all your intercooler hoses and clamps?
Someone else already stated that the fuel pressure should rise 1:1 with boost. I have a electrical fuel pressure gauge on the pillar to make sure. They aren’t cheap but I feel much better knowing my fuel system is working properly.
HTH


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Voltage is fine..checked that..had fuel gauge running off the rail to my windshield..fuel pressure is great
 

Turbobuick#1035

New Member
Jun 4, 2018
21
1
3
40
check to make sure the positive battery cable isn't hitting the downpipe
Will do
Check if the air intake pipes are sealed correctly/tight. What are you using for air intake? Could be un-metered air entering behind the Mass Air meter. Is your plug gap correct? Boost pressure? If above 12 lbs turn it down.
everything is tight..plugs are brand new. .28 gap every part swapped out was right off another GN that was running perfectly
 

Turbobuick#1035

New Member
Jun 4, 2018
21
1
3
40
Ran into this a couple of years ago I did the same thing for parts .took a good module off a running car same problem. So after chasing the problem for hours .We decided to go with a brand new module out of the box and coil and it fixed the problem.
Don't know why or how but it worked
Put the parts back on the running car and it didn't have the problem that the other car had
The coil pack and module swapped out was off a perfectly running GN.
 

Turbobuick#1035

New Member
Jun 4, 2018
21
1
3
40
Ok guys see if you can think of something as I’m outta options here. Car starts fine,idles fine and runs fine at normal driving. Once I start to get on it and boost starts, it hesitates and even a backfire will occur. Here’s everything I’ve swapped out with good known working parts to try this process of illumination. I’ve changed a the coil pack and module,I have a MAF translator so I put a new MAF on there nothing.I even went back to a stock MAF, i’ve swapped out the O2 sensor, I tried a new map sensor, fuel pressure is fine fuel pressure builds to 60 and more before i let off so it’s not running lean. The battery is fine the alternator is fine, there no wire alternator wires or battery wires touching any of the headers or down pipe. I change the computer I change the chip that did not fix the problem. The cam sensor cap was changed. Changed the wires, put new plugs. TPS is good and set correctly. The problem is still occurring. What else could it be? Any suggestions?
I should have said fuel pressure moves as demand get greater..alky turns on as it should. It starts at 5 to 7 lbs of boost I’m not even getting to wot
 

TurboBuRick

Moderator
Staff member
Feb 18, 2006
9,176
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South subs. of Chicago
You have a cam sensor issue. Did you check the wheel? What kind of cap did you swap? If it’s a Casper’s, get rid of it.

Make sure the cam sensor wheel is not moving around. Make sure the tab on the wheel is not broke. Any play at all is a problem. Focus close on the cam sensor..
And put a stock cap back on it...
 
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