misfire/pop on boost PLEASE HELP

[Loosenut]

I just got done putting my motor back in the car. I drove it 150 miles with the wastegate disconnected. It ran great at all rpms. I then hooked up the wastegate with a very low boost. As it comes up on boost it starts to pops and bucks like its misfiring. I have been going nutty trying to figure out the problem.

Heres the car.

86 gn with new .20 over girdled lower end, pro ported intake and heads, new 210-205 broken in right, te64e with 3k on it, mease downpipe, new cam sensor, new r42 ac plugs gapped at .030, new msd wires, new 340 pump with hot wire kit, new billet reg. set a 45 psi, new translator plus with extender chip, new 72 lb. injectors, ground extender, all grounds new.


Thing I have already done to try to fix it:

checked maf, load tested all power wires and grounds, replaced plug wires, coil pack and module, crank sensor, coolant temp sensor, o2 sensor and circuit, adjusted boost, adjusted fuel pressure, replaced translator, checked vacuum, adjusted tps, reset cam sensor, checked terminal tightness on the pcm, injector harness.

IM out of ideas. Has anyone had a similar problem or have any idea how I can fix this.

PLEASE HELP. Im almost out of hair to pull out!

Any help would be greatly appreciated.

Andy

 

[jastrckl]

fuel pump/pump voltage/fuel filter/fuel pressure regulator? I'd check and make sure your fuel pressure is increasing with boost as a start.

 

[TIMS87GN]

I'm still learning here too, but this sounded familiar and I'll throw this out to help. With that disclaimer said I'm going to point you to your translator.

Check your dip switch positions in the translator. Switch #3 can make a difference if it is set wrong. I believe it should be set to "off" if you are running the extender. (Guys please correct me if I'm wrong on this!) I had a non-extender in mine with the switch set wrong. When I put my extender in it cured my detonation problem at only 12#s.

I'm no expert, but I hope it helps!

 

[Maltman]

Ditto on what Tims87gn said....same symptoms....same solution!

....thanks to TurboBob

Here's the thread:

http://www.turbobuick.com/forums/showthread.php?s=&threadid=54341&highlight=miss+at+wot

..you'll notice how early Bob chimed in an how long it took before I noticed it....ticks me off that I missed his post.

Let us know if that helps.

 

[TurboBob]

He has an Extreme, for which the position of Switch 3 doesn't really matter.

But, the specified dip switch settings for an extreme are On On On On.

I'm waiting on some TL files....

Bob

 

[83ttypecooled]

misfire

Hi,
No wonder only 4 have responded out of 81 hits. This is a tough one... Have you checked fuel pressure under load? I know you have a Walbro340 installed, but this problem sounds like a lean misfire. I went through this trouble, ended up being the fuel pump. Do you hear fuel rushing through the system on key up?
The other possibility would be ignition, and once again, I know you have replaced all the pertinent components. Do a coil output test for the heck of it. You never know....
As Sherlock Holmes says, "if you remove the impossible, then what remains must be the truth" Good luck!

Dale

 

[86gn]

Always worth a look is to make sure the keyway in the cam sensor is not missing,Mine would do the same thing under load there was enough force to move the window under the cap.

 

[Loosenut]

Thanks for the help, please keep it comming!

The fuel pump is brand new from Racetronix with their hot wire kit.

The o2's are good, its not leaning out.

Andy

 

[Mustang 1]

You will think that this is stupid, but I have had my share of experience with this problem more than once. Check the plug wires, especially look at the ends at the coil pack. Lokk for rust and/ or corrosion. Also, look for rust or corrossion at the terminals on the coil pack. If any exist, replace the effected parts. This has been the cause of the same problem for me. Do not assume that the wires are good! I did, but my Taylor race wires were bad in less than 1 year! Also, one other time, popping and sputtering under boost, I assumed the fuel pressure was inefficient, so I turned it up to spec and the condition worsened. Upon changing the gauge, the fuel pressure was at 80 psi at idle! So, the bad gauge cause me to run excessive pressure, which resulted in the same type of problem. Hope that this helps!

 

[Loosenut]

Ok, heres an update.

Just started it and disconnected the cam sensor and same problem.

Also, checked fuel pressure and it is at 40 at idle and climbs to about 50 on boost. The needle fluctuated a little when it began to sputter.

Im outta ideas here......

Andy

 

[Loosenut]

Mustang, I have brand new MSD plug wires and the terminals are spottless.

Thanks
Andy

 

[milesengineer2]

I am not sure this will help at all.

What kind of Fuel Pressure Regualor are you running?
I had the same problem. Mine turned out to be the regulator. I was using the holley one with the threading in the vacuum inlet. Turned out that the threads were not very accurate and tight with the screw in the top of the regulator. As more boost was being blown it actually made the pressure flutter due to the air getting around the screw. My fuel pressure would actually go from 52-65, at 17 lbs of boost. Alky was turned off and base fuel pressure was around 38, static. In second or third at a wide open burst the 0/2's would jump to almost 900. Took forever to find the problem, now the car runs like a dream.

HTH