Backfire through throttle body at boost

[slick6732]

To start out, the car was parked for about two months in storage, due to Indiana winter. I did start once a week throughout the storage.
My problem is when I get to about ten pounds of boost, I get a backfire or pop through the throttle body and the boost gauge jumps to about twenty pounds very quickly, before I can let off the throttle. Does it moving when rolling into it just enough to build boost. Have only did it twice in fear that I may cause damage to internals, jacking around with it. What I have done: Pulled both valve covers and checked to see if all rockers are moving, which they are. checked all hoses from breather up to turbo for holes and to make sure one had not slipped off. Not getting any strange reading on scanmaster!
Although today running with the hood open I was listening for vacum leaks and I could hear a grinding noise at the down pipe puck and if I move the lever underneath that controls the puck the noise goes away, the sound is almost like the puck is riding on the fins of my turbo, could it be related to the problem I am having with the backfire? It is a th 3" dp
Any suggestions would be great, stumped and need places to start looking, downpipe is coming apart tonight so i will keep you posted on what I find in there. Thanks in advance

 

[HelloBozos]

Your over boosting!!,Might have to open up the puck hole on the turbo or get new vacume Actuator,Lastly might be running out gas,check pump an change fuel filter

Enjoy!

 

[slick6732]

Thanks, weird you brought up the gas! Left it sit outside one night before I started driving it again and someone stole all the gas out of it and left me their hose!! Filter is probably a good place to start!!

 

[Ttype6]

To start out, the car was parked for about two months in storage, due to Indiana winter. I did start once a week throughout the storage.
My problem is when I get to about ten pounds of boost, I get a backfire or pop through the throttle body and the boost gauge jumps to about twenty pounds very quickly, before I can let off the throttle. Does it moving when rolling into it just enough to build boost. Have only did it twice in fear that I may cause damage to internals, jacking around with it. What I have done: Pulled both valve covers and checked to see if all rockers are moving, which they are. checked all hoses from breather up to turbo for holes and to make sure one had not slipped off. Not getting any strange reading on scanmaster!
Although today running with the hood open I was listening for vacum leaks and I could hear a grinding noise at the down pipe puck and if I move the lever underneath that controls the puck the noise goes away, the sound is almost like the puck is riding on the fins of my turbo, could it be related to the problem I am having with the backfire? It is a th 3" dp
Any suggestions would be great, stumped and need places to start looking, downpipe is coming apart tonight so i will keep you posted on what I find in there. Thanks in advance

You have a bad ignition coil.

 

[TurboBuRick]

Bump the cam sensor slightly ccw.

 

[adowningusa]

Had a similar issue with my previous GN. Turned out I needed to replace the valve springs.... Just a thought.

 

[kidglok]

You have a bad ignition coil.

this did the same thing to me

 

[slick6732]

Thanks for the posts, Valve springs are new, Will swap out coil with a known good one I have here, checked cam sensor. While spending half the day going thru the car I noticed the elbow coming out of the turbo was loose actually had two bolts backing there way out!! Just tightened them up, but off to work so I won't know if that makes a difference until tomorrow!!

 

[slimtastic]

if theres a poping noise in the intake and you see the boost flutter up sharply then you could be getting a lean backfire in the intake

 

[SpeeednV6]

same thing happed to me at one time. I replaced the coil...solved the problem. I made sure the sparkplugs were gapped tight.

 

[slick6732]

Update time, Have went thru all grounds, vacuum lines, fuel pressure is good, battery jumps around from 12.1 to 13.2 constantly on scaanmaster while cruising. Somehow I have gotten rid of the backfire, but the car runs and idles great. When you roll into it (not hard) just enough to build some boost, it will come alive and pull strong to about 12 pounds of boost then it falls on its face, kind of flutters. Any thoughts? Coil? MAF? Going to change plugs over weekend and check wires! Appreciate all the help you all have given me so far

 

[groumoutis]

Are you hearing a noise when it falls on its face? Kind of like a farting sound? If so check your connections/hoses from the turbo to the intercooler and from the intercooler to the throttle body. I bet one is loose. I need to get over to Muncie and meet some of you guys on the east side of the state.

 

[GNRick]

Happened to me once. Blew the up pipe off. Turned out to be a dead spot on TPS sensor.

 

[Chuck Leeper]

"battery jumps around from 12.1 to 13.2 constantly".............Not right. U should find this problem, and correct it.

 

[slick6732]

I agree Chuck, I just can't seem to find the culprit, Battery is new. May have to take it and have the altenator checked, supposedly it has a 300 amp altenator on it.....Lost for now!!!

 

[Chuck Leeper]

I'd start w/ that "300A" alternator.....
Also, bad grounds in the system can/will send the volt meter nuts...
Check volt drops across all the circuits. Check for hi ohm readings on all grounds.
I just recently had this on my 55. [All new install w/ HD cabling, everything bolted w/ star washers, etc]
The gas ga was whacked. I checked the ohm reading on the ga/body ground...22 ohms. Should be <1, IF all's well.
My volt meter was also reading funky.[low by at least a volt]. I checked the welded ground studs for the gauges and pcm. 26 ohms! Cleaned, added no nox to the connectors, retightened. Now it's<0.2 ohms. Volt meter is now at 13.7/14.1.

 

[mgmshar]

Whenever I hear about a car running like yours, where it acts up after reaching a certain boost level, I immediately think of two things...

1. MAF going bad.
2. Coil pack going bad.

It "could" be a lot of things, like some of the things others have previously posted, but in my mind MAF and coils are the most likely. Try eliminating those first by swapping them out with known good parts.

And yes, if your voltage is fluctuating between 12 and 13 volts while cruising, something is wrong in the electrical system, which may or may not be contributing your other problem. 300A alternator? Wow, that thing must be huge! The stock one is only 120... I would really wonder about that alternator. Maybe consider swapping that out with a known good one to see if your voltage stabilizes. Your voltage should be relatively steady while driving at a constant speed. The only exception is when something that draws a big load turns on, like the radiator fan, at that time the voltage will drop for a second and then come back up to normal. Otherwise, the voltage should stay stable within about a half volt range if you're driving at a constant speed.

Good luck,

Mike
Sent from my HTC Droid Incredible using Turbo Buick

 

[slick6732]

Good call on the coil !!!!!! Changed it out today and running like a champ again Battery voltage still jumping around, but I will find the right wire eventually! Thank you all for your input, you guys are all great!! Tons of knowledge in this place

 

[slick6732]

I'd start w/ that "300A" alternator.....
Also, bad grounds in the system can/will send the volt meter nuts...
Check volt drops across all the circuits. Check for hi ohm readings on all grounds.
I just recently had this on my 55. [All new install w/ HD cabling, everything bolted w/ star washers, etc]
The gas ga was whacked. I checked the ohm reading on the ga/body ground...22 ohms. Should be <1, IF all's well.
My volt meter was also reading funky.[low by at least a volt]. I checked the welded ground studs for the gauges and pcm. 26 ohms! Cleaned, added no nox to the connectors, retightened. Now it's<0.2 ohms. Volt meter is now at 13.7/14.1.

Have taken off and cleaned all ground cables, except for the fun ones on the back of the block. They are next, will also have the battery and altenator checked....Thanks for the help