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Discussion Starter · #1 ·
The engine won't take more than 10 - 12 pounds of boost without backfiring and having 15 degrees of retard.

Coil pack and module are good.

Fuel pump is good.

Fuel pressure rises appropriately with boost.

Spark plugs and wires are new.

Cam sensor is new and checked for proper setting multiple times.

Fuel injectors are not clogged.

Each injector is getting proper signal.

Tried multiple chips just to see if that made any difference.

Gas is good and has been replaced.

Turbo was just rebuilt two weeks ago and functions well.

The car has perfect running and driveability up to 10#

The maf has been swapped with a known good one.

I can't remember what else was checked but these are the ones I can remember.


As far as the question of what has changed since last time the car ran right at high boost here is the answer. The engine was rebuilt over the winter. It is ready to come home from the shop but the engine has the condition described above and we are out of ideas of what to check. This is a reputable shop that has years of experience working on these cars. I will not identify the shop because it is not necessary and I don't want to imply that this is their fault in any way. I just want my car to come home and I need help with ideas of what else we can check.


What else can I check? Thanks.
 

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YOU KNOW MY NAME!
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5,673 Posts
There's a hose that goes comes off the boost solenoid that splits into two. If you mix them up it won't boost over 10 pounds. Doubt it would make it backfire tho.
 

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mine did the same thing it ran perfect till i hit 10 to 12 pounds of boost and would backfire like crazy and it was my coil pack.i wouldnt rule it out.
 

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Older than dirt
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"Spark plugs and wires are new." What heat range/brand, are the plugs? What are they gapped at?

What do you have for data recording?
 

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I have had this issue a few times. 1 coil 1 module and 1 intercooler hose clamp. Each time it did exactly what your talking about. gets up to 12#'s of boost then POP. and nothing. If your coil and module test good with that tester that does not mean they are good. I had mine tested with one of those fancy testers and it said the coil was good but it was not. Check those 3 things and you will find your problem.
 

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Older than dirt
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I try to use the Casper tester while the coilpak is still hot...
 
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