Brand New ACDelco Coil Pack & Module, Still Backfiring/Popping at WOT...

[thepremier]

Just as it is decsribed in the title, I am still experiencing backfiring/popping under the hood at WOT. I surely thought that replacing the Coil Pack & Module with brand new ACDelco parts would solve the problem, but to my disappointment, it did not go as I had hoped.

What else could be the cause of this problem, because at this point I am clueless.

Any help will be greatly appreciated.

Thank You

 

[xXch0dyXx]

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[Royal-T-Ltd]

How much boost are you running?

Depending on how much boost you are running, you could be blowing out the spark... i had this problem a while ago and now run a TIGHT .032 gap instead of the .035 - some people run even smaller gap..... double check your plugs... EASY and CHEAP fix and insurance. HTH:wink:

 

[Evans Ward]

Known good plugs wires on the car? Do you have another set of plug wires you could throw on there? I just had the same problem and it turned out to be a faulty wire letting go at the insulator connector under the boot. Are you sure too that your car is getting enough fuel at the boost level you are running? If not sure, verify. HTH.

 

[ROYAL_6]

double check that you hooked up the wiring from the module to the coil pack the right way.... also check your plugs, and your spark plugs wires... start with the simple stuff first, believe me it is alsways the smallest and dumb's thing..... also check the gap on your plugs... make sure they aren overly gapped...

 

[MikeL.]

#3 exhaust lobe...wiped

....that was my popping under boost. If all the other suggestions on the above posts check out okay, pull the valve cover and see how much movement the rocker arm has compared to the others. This was my excuse to go roller :biggrin:

 

[VadersV6]

Just rotate the motor till #1 intake is open, then check the #1 exhaust rocker/pushrod for slop. There should be no lash. Rotate and open the #1 exhaust then check the intake rocker/pushrod for slop. Once again, there should be none. Go down the line and check all of them. No need to fire the motor up with the valve covers off and splash hot oil in your face. Pop the cam sensor cover off and feel the interrupter ring/shaft for excessive slop/damage, and check that the ring hasnt damaged the sensor groove in the cap.
Also, how long does it take for fuel pressure to drop after shut down?

 

[87NAT]

Check crank sensor for rubbing/cracking or just plain broken. That was my problem.:redface:

If popping/sputtering under high boost drop plug gap to .28 and see if that helps.

 

[Louie L.]

Assuming that you are sure that you have adequate fueling ,timing and your MAF is fine try this.
Start the car. Un plug the CAM sensor and go check for popping at boost. remember engine wont re start with out plugging sensor back.

 

[GNRick]

A scan tool might help. Mine indicated a bad TPS sensor, although it seemed to work fine with key on but engine off.

 

[thepremier]

At WOT, the knock reading on my Scanmaster was at a 19.0 I bought the motor from Nick over at ArizonaGN, and he also put the motor in my car, so I'm pretty sure he tuned everything appropriately.

I was hoping that it was something as simple as a bad coil pack or module, but it seems to be something more complex, so I will just go ahead and let somebody who know what he is doing figure out the problem.

I guess I will be making a call to him, and hopefully he can figure out what the problem is with the motor. I appreciate everybody's input in regards to my problem.

 

[meanchicken]

Please post back once you know what the root cause is.

Not trying to high jack your thread, but my newly bought 87 is doing the same thing. Under WOT and low in the power band (like right after shifting into a new gear), the boost shoots straight over 15 and into the red (pegs the OEM boost gauge). The engine feels like it loads up a bit as the boost builds and then I get the "POOF" ...followed by nothing for about a second except a cloud of smoke out the pipes and then the engine sputters back to life and power slowly comes back.

Mine is mostly stock except for an unknown old school chip the last owner put in it several years back.

I'll be doing the spring cleaning this weekend and hoping I figure out what the cause while doing it.

This string is giving me a lot of things to look at along the way, but I really want to know what you find out from your mechanic.

Thanks!
Tim

 

[BlackMetal]

Also interested to see what you find out. I had popping/sputtering problems a while back but was lucky enough that replacing the coil pack cured all.

Keep us informed.

 

[TurboBuRick]

Also interested to see what you find out. I had popping/sputtering problems a while back but was lucky enough that replacing the coil pack cured all.

Keep us informed.

I thought yours was still missing after coil pak & module then someone recomended that one sensor...or mabye I'm wrong.

 

[GNRick]

Hi,

Any update? Thanks.

 

[TurboMonte 2]

+1 for Crank Sensor--clearances inside & out of interruptor ring?? Could be an inexpensive/ relatively easy fix,,,

 

[thepremier]

Update... Found The Problem

As my prior post described, I was having backfiring/popping under the hood at WOT.

The problem actually turned out to be that I was not getting enough fuel pressure. I went out and purchased a fuel pressure gauge kit from kirban, and installed it, and it came back with a 32 psi reading at idle.

Next I installed the new Walbro 340 fuel pump kit + hathotwire harness, and the first change after I completed the installation was that the fuel pressue reading on the gauge jumped up to 40 psi at idle.

At this point, I no longer had a rough idle, and it was now nice and smooth.
Next I took it out for a test drive, and I couldn't believe the effect that the new pump and hotwire had on the performance.

The car seemed like a completely different vehicle, no more popping, backfiring, or any other issues...

Needless to say, I was very happy to finally figure out the problem and get my GN running hard once again.


Just wanted to share this information with you guys, and once again, thank you for all of those who helped me out during the process.

 

[Aztlanahauc]

Mine was doing the same thing before it popped a head gasket...


Looks like a Walbro and hotwire kit are added to the list now.