Backfire at WOT

[85TurboTtype]

Hello,

It has been quite a while since my last post. I have had 3 children in the last 4 years! Twins in the last year alone!! Ya, I know... I'm crazy.

At any rate, I can idle fine and get into the gas until I'm at full WOT. As soon as I get into it it starts to snap, crackle, POP! I put new spark plugs in it last year. AC 42's gaped to 35. I just rechecked the gap today. I have 2 fuel pressure gauges that are reading appropriate fuel pressure. I have not checked my cam sensor yet, but haven't been near it in years. I have the LS1 MAF with trans plus as stated in my signature. I do have a scanmaster and have checked the most common settings for all of the readouts. The BLM's seem a bit high at 140, but I did just reconnect my battery. I'll get all of the specks and post here in a few minutes at idle, as I can't WOT and give those numbers because of the BACKFIRE! Please start go shoot some ideas my way if you could. I also, need to grab a Trans Plus Manual. Where can I download the PDF for that?

Thanks everyone!

Matt

 

[forzfed]

Sounds like you might have a bad coil. Have you checked the resistance?

 

[85TurboTtype]

That I have not. I have heard about doing this before in my readings of other symptoms. What would be my process for doing this please. That sounds like an easy first step in the diagnosis.

Thanks,

Matt

 

[pajo]

+

I would say all of the above - either coil or module or plug wires ..?

 

[85TurboTtype]

Brand new MSD 8.5 plug wires too. Thanks for the reply.

 

[pajo]

forgot

And forgot to say welcome to the club of twins - I have 5 kidsand the last two were twins - boy and a girl- Thank you GOD.

 

[forzfed]

That I have not. I have heard about doing this before in my readings of other symptoms. What would be my process for doing this please. That sounds like an easy first step in the diagnosis.

Thanks,

Matt

Pull the plug wires off each coil and put your multi-meter to the resistance(ohm) setting, should be set around the 20k range. You should see approx 12-13k of resistance going across the terminals of the coil, coil runs front to back.

I can't see it being a plug wire because I would think it would be breaking up right from the start, but it could be a module. When my coil went it ran good but every once in a while it popped, till it got much worse.

 

[bmackinnon]

Agree that it sounds like a failing coil pack... but would like to verify your statement of 2 fp gages reading appropriate pressure... you HAVE verified that the fp pressure is rising exactly 1:1 with increasing boost pressure.... and HOLDING.... ie... you are watching the fp while driving and it is rising in relation to boost..... correct??

 

[85TurboTtype]

Pull the plug wires off each coil and put your multi-meter to the resistance(ohm) setting, should be set around the 20k range. You should see approx 12-13k of resistance going across the terminals of the coil, coil runs front to back.

I can't see it being a plug wire because I would think it would be breaking up right from the start, but it could be a module. When my coil went it ran good but every once in a while it popped, till it got much worse.

I will try this tonight or tomorrow morning and give feedback ASAP. Thanks again!

 

[85TurboTtype]

Agree that it sounds like a failing coil pack... but would like to verify your statement of 2 fp gages reading appropriate pressure... you HAVE verified that the fp pressure is rising exactly 1:1 with increasing boost pressure.... and HOLDING.... ie... you are watching the fp while driving and it is rising in relation to boost..... correct??

I'm 90% sure this is true. I will also watch this more closely the next run after I test the ohms. If the ohm test fails, then I will attack that first!

 

[85TurboTtype]

JUst so I know, what is the recommended coil for our cars and where would one get them? FRom mike at full throttle?

 

[forzfed]

Get a Delco one, not sure if Mike sells thems. Check Gbody parts too. I lucked out and found one at a local dealership here for $57, it was sitting on their shelf for 10yrs and they just wanted to get rid of it. Here is a link to one...
HIGHWAY STARS - nos4gn Buick Grand National Parts 1986 1987 Buick Turbo Regal T-Type GNX parts

Also, if you have crazy high resistance then the coil is shot.

 

[85TurboTtype]

Just so I'm 100% sure on this procedure. I'm using my multimeter on the ohm setting of course. Then putting the red (+) on one terminal and the black (-) on the other terminal to get a reading? Front to back like stated earlier...... Thanks everyone. You guys here are always very helpful! :biggrin:

 

[forzfed]

Just so I'm 100% sure on this procedure. I'm using my multimeter on the ohm setting of course. Then putting the red (+) on one terminal and the black (-) on the other terminal to get a reading? Front to back like stated earlier...... Thanks everyone. You guys here are always very helpful! :biggrin:

Sounds right.

 

[85TurboTtype]

Sounds right.

Well, good news and bad news. The readings were 11.91, 12.80, **** Nadda! So, I guess I have found my problem, but now I need to buy a new one! Thanks everyone for your input. Very appreciated :biggrin:

 

[bmackinnon]

Yup.... 11-13k is good, ****nada is not...:tongue: ...use AC Delco for sure....and remember that the new coil pack will probably come with the spade terminals straight.... they don't pre-bend them so you don't have to straighten them, connect the wires to the module, and re-bend them...causing potential fatigue crack/break of the terminal.... once you connect them bend them sideways to the correct angle so they don't dig into the potting mat'l of the module , and potentially short the coils... as shown here:

http://www.installationinstructions.com/FYI/ccci-failure.pdf

Oh, and if you find the potting mat'l of the module has turned to nasty goo, you might want to think about shopping for a module also (AC Delco, as well), as the gooey module may not be far behind the coilpack...

Just a fyi....

 

[TrAb]

Mine was doing this exactly and it turned out to be the coil pack. It was one i got from autozone, i replaced it with a delco one and now its doing great.

 

[TurboBuRick]

One more thing, make sure your not over boosting. Check your boost lines on the solenoid and actuator.

GL

 

[85TurboTtype]

And forgot to say welcome to the club of twins - I have 5 kidsand the last two were twins - boy and a girl- Thank you GOD.

It sure is fun!! Let me tell you!!

 

[tzque]

I have had the same problem discussed on this on thread . I have one question . I also need the harness that they coil pack plugs into . My friend suggest that I get one from the junk yard . What do you guys think and where can I pick one up . I wish I head read this earlier so far I have installed a fuel pump and hot wire kit two things I already needed anyhow . Thanks guys