86'gn Backfire/sputter Under Boost?

[SNAKE250R]

Someone Please Help! My 86' Gn Started Backfireing Under Boost Awile Back,i Thought My Boost Was Too High So I Kept Backing Off,no Help.called Mike, Fullthrottle,he Said Do Tune Up.installed New Hp Feul Pump W/hot Wire,boost Gauge,new Adj.fuel Pressure Reg.new Ac O2 Sensor,ac42ts Plugs,cleaned Iac & 9"k&n,fuel Filter,ac Pcv,wires,adjusted Tps .44 - 4.56 On Scanmaster, Car Is Mostly Stock W/flowmaster Exhaust,77k Miles,poston Thumbwheel Chip,gutted Cat And Other Mods Listed. I Got All That Done,ran The Car 1 Blast Good,second Blast Backfired Threw Intake Again,this Time With Code 34.called Mike,now Have A 3" Impala Maf W/translator.now No More Codes But Still Backfires Or Misses Under Boost At 10psi But Less Violent. I Have Boost Set At 17 Psi.fuel Pressure 40psi-no Vacuum,translator On On On Off,base 4,ran Best At 2 On Wot.car Seems Rich With Over 800 Mv Under Boost.i've Tried Different Wot Trans Settings And Fuel Pressure Settings With No Help.

 

[Razor]

Maybe chip is the problem?

Or...

Whens cars pop under load, typically its ignition related. Meaning plug gap too open, bad wires, or bad coil pack. The higher the boost the worse it gets.

So if you gap your plugs at .032, wires are new.. then my bet is coil pack or ignition module.

 

[bmackinnon]

Coil pack/ignition module.... almost for sure..... ohm the coil pack between pairs of towers... should be 11-13k.... if so, 'probably' just the module. stick with AC Delco..

 

[at7we2]

I've been dealing with the EXACT same intermittant symptoms for a LOOOONG time now (approx. 3 years! ). Still haven't been able to track down the problem. While trying to diagnose the problem with my car I've done a lot of online research into these symptoms. The symptoms you described apparently have several different possible causes, but the most common (from what I've read and heard from talking to local Buick owners) is *usually* the coilpack, as stated in the previous posts.

I've either replaced or temporarily swapped-out almosts every component in the ignition and fuel systems (some of them multiple times!), I've run bypass wires for this and that, I've checked grounds, installed new grounds swapped chips, Translators, ECMS, MAFs - it still pops and stutters intermittantly.

Good luck, I hope it's a simple, inexpensive fix.

Rob

 

[challengermike]

I am sure you know but check to make sure that the positive battery cable isnt hitting the exhaust manifold when the engine torques up.

 

[SNAKE250R]

Thanks For All The Replys, I Was Planning On Checking The Positive Cable.i Will Check The Coil Packs And Module With Plans Of Replacement Both I Have Read Threads On But I Needed Some Reasurance.i Should Of Posted With You Guys Sooner Rather Than Try To Get Tech Help From Mike At Fullthrottle,he Is Helpfull But Seems Like He Couldn't Be Botherd Or Is To Busy.plugs Are Gaped To .35 ,any One Know What Base Settings To Start With On Maft With 3" Impala,also My Iac Is 68 At Idle And I Cant Seem To Adjust Down To The 20-30. Thanks Again

 

[GNRick]

You've probably come across my fix if you've been able to search on this board. When I had that problem it was a bad TPS sensor. Even though it checked out with key on and engine off, my scan tool showed that it had a drop out under load. New sensor fixed it. I've also read a bad crank sensor can cause problems like you described.

 

[SNAKE250R]

I Ordered A New Ac Coil (ac Part That Said "made In China" $114.00) With New Gasket ,installed It ,drove The Car And Fixed My Problem With A Seat Of The Pants Holly #@ht! Also Idles Smoother. I Just Need To Fine Tune My Fuel,boost. Thanks For All The Help Guys!!