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Discussion Starter #201
My parts came in yesterday and went ahead and installed the fuel pulse damper this morning. The short term fuel trims went more negative as expected from the previous install. The car runs more smooth but the stumble is still there, but this time instead of stumbling hard at 3000-3500 rpm and triggering a P0303 with the CEL staying on, it shifted the stumbles back down to 2600-3000 rpm triggering the CEL, but it goes on for less than half a second and then stays off. Below 4000 rpm, the short term fuel trims go negative as low as -15%. I wouldn't have thought that a damper can have such an effect on afr that much.
 

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You have to have something funky going on with that stumble. There is no reason it should be back...

Maybe fuel pump is on it's way out?

Have you thought about new rails?
 

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Discussion Starter #203
You have to have something funky going on with that stumble. There is no reason it should be back...

Maybe fuel pump is on it's way out?

Have you thought about new rails?
I don't think the pump is going out. It's just the typical stumbles when going 1000cc and up injectors. The harmonics in the fuel line shifted the stumbles lower than where it was. My car is a little different. It didn't stumble on the older Cobb stage 2. OTS V3.33 and up, it stumbled hard. It just needs fine tuning. It's scheduled for a retune to take advantage of the higher compression and to remove the stumble.
 

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I know what you mean when you say your car is weird, mine was weird too... I never really even had the stumble. I guess if I had to point out a time when I had it, the car was completely stock. I ended up building the lines with the older style FPR and a damper on the return because it just seemed like a good idea lol
 

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Discussion Starter #207
I will be experimenting with another fuel damper to see how it affects the stumble. It will be the OE damper from an older STI, but this time on the return line.
 

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Discussion Starter #208
The quick connect to AN fittings leaked heavily. I had to resort to cutting the IAP stumble kit and installed the return side damper. It smoothed out the stumbles a little and the CEL doesn't stay on as easily. The feed side will have the Radium Engineering damper go back on, but this time with the plastic quick connects. Those have not leaked on me, yet(knock on wood).

Also, my HKS Premium Suction kit arrived today. I'm going hard turbo inlet and MAF.
 

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I have considered the aftermarket fpr. I have one ready to go in. I thought it would go away after installing the IAP stumble kit, which it did, but not for the bigger injectors.
I'm upgrading injectors soon... so I'm sure I'll eventually be doing rails and FPR as well. Sigh. It's only money, right.

Just need COBB to release more info on the flex fuel option so I can get my bearings on what to start collecting.

These cars and the stumble are so finicky.
 

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Discussion Starter #212
I'm upgrading injectors soon... so I'm sure I'll eventually be doing rails and FPR as well. Sigh. It's only money, right.

Just need COBB to release more info on the flex fuel option so I can get my bearings on what to start collecting.

These cars and the stumble are so finicky.
I kinda curious on how Cobb will do flex fuel. I did the Delicious Tuning kit.
 

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Discussion Starter #216
I did the test drive with just the Tomei fpr and 06 STI return line damper. The stumble was still there and it set off the CEL, but it didn't stay on. It did however, smooth out the stumbles a bit. I decided to go ahead and install the Radium Engineering fuel pulse damper with the boost/vacuum port. It removed most of the stumbles, but it's very faint. I think another driver will not notice it. Now it just needs fine tuning. It does run a little rich below 4krpm and idle.
 

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Discussion Starter #219
I would say for the initial drive on the freeway, my temps are about 176 when normally around 195 at 65 degrees ambient. A little too cool but it would be great at the track based on this.
 
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