hey there my name is Kees im new here i just bought my firebird 86 LG4 a couple of weeks ago and already had a lot of problems with it and i still have a lot of problems ahead so you proabably will be hearing from me often.
One of my biggest problems of the moment is that when i slam accelerate the accelerator the engine drops dead for a split moment and then picks up and pushes the rpm needle up in no time. I only have this problem from idle both running in park/neutral and in all drives. i thirst thought it had to do with the igintion but the sparkplugs/wires/vacuum advance and ignition module have just been replaced by myself. The only thing i can think of now is that it is the carb (it`s a Holley 600cfm) another thing is that there is no ecm control anymore in the engine there is a normal ac-delco HEI ignition and all sensor wiring is removed.....strange. So where do i have to look at when i start investigating the carb the mixture is good 1 1/2 screw out on both sides tand the (electric)choke is disabled, probably jammed inside.
Now im looking to this incredible messageboard wich i've learned a lot from already for help.................

 

My guess would be over carberation. But I could be wrong. Something like that sounds like the fuel/air velocity dies for a momment, makes the fuel drop out of suspension, and then picks up and improves as air velocity increases through the intake and carb. The stock LG4 carb, I BELIEVE, but am not sure (so please, nobody kill me) flows something like 600+ CFM, but has vaccume secondaries. Are those Mechanical or Vaccum secondaries? If you said, I must have missed it.

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86 IROC-Z, Retired for winter, weird oil leak (drains out in about 3 minutes), new 355 other than that, TPI, 700R4, edelbrock headers, removed AC/Air pump, heater plate conversion - no heater (loL). 14.8@90MPH

Next project (think I'm going to scrap the IROC)- mid 80's monte carlo, 383, edelbrock performer RPM intake, cam, holley double pumper carb, sportsman 2 heads, NOS. Hoping mid/high 12's on motor, mid 11's on spray.

 

Slow is right, that's classic lean bog. Too much carb will cause it. Also, a poorly functioning accelerator pump will do it.

Does the car go a little then die? If so, try smaller pump squirters. If it's flat right off idle, check the pump adjustment. If that's OK (no clearance between the duration screw and the lever) try a pump cam kit.

What carb and cam?

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"So many Mustangs, so little time..."

 

It`s a holley 600cmf with vacuum secundairy
and im pretty sure it`s not to much fuel because then the problem wouldend be the same in park and drive right. with pump do you mean the main fuel pump or the accelerator pump if it's the acceleretorpump where is that located on a holley and how can i adjust it

 

I mena the accelerator pump. Your problem is too little fuel at that critical instant, not too much. The pump itself is on the driver's side of the fuel bowl, underneath; the linkage is on the side of the bowl in front of the throttle lever. You can't miss it.

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"So many Mustangs, so little time..."

 

RubyRed,

Welcome aboard! If you have a problem (or a list of them) you've come to the right place. You'll get lots of opinions, support, and some very expert advice from the many members. Stop in any time with questions or problems. We only ask that when you have an experience that can help another member, please post your input.

Slow Iroc and RB (as usual) are right on the problem. It sounds as if the mixture is lean on throttle tip-in. The accellerator pump would get my vote as well.

Again, welcome aboard, have fun, and come back often.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

RR,

Incidentally, the accellerator pump is located here:



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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0