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Discussion Starter #1
I have a 1996 GST with many "bolt ons".

THE PROBLEM: Runs great until I drive about 15 minutes, then once really warm, the car bucks when the turbo starts to boost. Happens in all gears, feels like the fuel is being cut off to the engine. Idles great, runs fine if I keep the turbo from boosting.

HAVE TESTED: The mass flow meter, plugs, grounds

Check engine light has been on since I bought the car (3500 miles ago) but explained by many as "normal" because of the extras. Car has 75000 miles and just replaced the timing belt.

The add-ons significant to this discussion are:

Greddy 18G Turbo (running about 18 lbs)
Greddy Intake
Greddy Front Mount Intercooler
Greddy BOV
New Iridium plugs and NGK wires
3" Down Pipe
High Flow Cat
Thermal Research exhaust
Larger fuel pump
Super AFC
Blitz dual solonoid boost controler
Stock injectors

Any ideas???
:confused:
 

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Stock injectors? Good grief, do you at least have an egt or even an a/f gauge? Thats a bit too much boost your running with stock injectors.
The check engine light might be the 2nd o2 sensor, but no one knows until you find out.
 

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Wires

Check your plug wires. If they are getting worn or have a small hole in one of them that will cause it to feel like its missing on a cylinder.

Reason is, When you accel and as the RPMs get higher and the boost hits, the computer ups the voltage to the plugs causing the spark to jump to a ground before it gets to the plug and it missfires.

Get another set of wires and see if that helps. Also, Turn the boost down to about 15# and see if that helps.

Another note. GET RID OF THOSE IRIDIUM PLUGS !!! :D
Get the NGK's, there only about $2 a plug and they work GREAT!
 

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Discussion Starter #4
Thanks.

I have an Air Fuel LED and super AFC, the older dial in kind.

EGT?

Have suspected the O2 sensor, but 2 mechanics have disputed. I'll test it.

Plug wires are new NGKs, doubtful since they were just examined w/ plugs. I'll test w/ Magnicore wires that I have.

Plugs are NGK Iridums! $36 for 4. I thought this was a GOOD thing !?! I know Platinum plugs are bad for this car.

I'm Planning 550 cc RC injectors from the local guys at TURBOCHARGERS.COM... do you recommend using a higher CC?

The engine feels like the fuel is sparatically cutting on and off when It's at full tempature and I boost over 4 psi. BUCKS.
 

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Elite DSMtalker
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Hummmm

Plug wires are new NGKs, doubtful since they were just examined w/ plugs. I'll test w/ Magnicore wires that I have
Hummmm..... Still would not hurt to try the other wires.


Plugs are NGK Iridums! $36 for 4. I thought this was a GOOD thing
IMO anything other than the regular ol NGK BPR7ES plugs, are just a waste of money.


I'm Planning 550 cc RC injectors from the local guys at TURBOCHARGERS.COM
550's should be just fine with the 18G. I think Road Race has the lucas 550's for around $290 for all 4.

boost over 4 psi. BUCKS
You might also check for a boost leak.
 

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Re: Hummmm

91TalonTSi said:


You might also check for a boost leak.
If it runs fine otherwise, I'd be willing to be this is it. Go to www.vfaq.com and find how to build a boost leak tester.
 

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Discussion Starter #8
If there was a boost leak, wouldn't it buck all the time, not just when warm? Plus w/ 17-18 pounds of boost, I would think it would have blown a hole in a leak by now. I'll test and let you know.

Will try the wires, I have them anyway and it's easy.

What's the value of knowing the exhaust gas tempature? Are the benefits worth the cost?

THANKS! Im going to plug in a datalogger and see what she has to say.
 

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re:humm

What's the value of knowing the exhaust gas tempature? Are the benefits worth the cost?
Its just another tuning method. The leaner you run, the higher the temp of the cylinders of your engine. So not only can you tune for max performance, you can also keep your pistons at a safe temp and prevent melting shit :) So yes it is worth it to me.

PS. On a side note, I would get 550cc Injectors ASAP. With the 450's and 18# of boost on an 18G, The Injectors are most likely @ 100%

Turn the boost down to 15# and see if that helps.
 

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Discussion Starter #10
It was a blown head gasket. Repaired and also replaced the boost controller. Runs like a bat out of hell now. Roasting the tires in third at 70 MPH.
 
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