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Old 09-05-2008, 01:10 AM   #12
AleroB888
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Location: Fort Knox area, KY
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Update

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Originally Posted by AleroB888 View Post
................But soon, as the car warmed up and the computer settled in, an off-idle stumble developed. Not just from a standing start, but also a hesitation when stabbing the throttle from a low rpm cruise...........

Quote:
Originally Posted by AleroB888 View Post
...........I got a Walbro 255 LPH fuel pump installed a couple of days ago, gave it a day for the computer to settle things in, and did a scan. It seemed to make the Envoy injectors work even better, and I should have left them in to see if the pump change would gain anything at the track..............

The jury is still out on the 35 and 36 lb injectors, the hesitation issue now seems to have been from another source, related to the supercharger. I have not had a chance to retest them, and now the 28 lb units are back in. Also, the 1999 runs about 10 psi less fuel pressure than the later models, and the stock pump is rated lower as well. I went to a later model FPR.

My first Walbro pump failed, as did an Autozone OEM unit. I tested an inline Walbro as a booster pump in a setup with the Autozone OEM, but no success on that yet either. Right now I have a second Walbro in-the-tank unit installed with wiring directly to the pump. I just made a 1200 mile road trip to sea level, never letting the tank go below 3/4 full. This should be interesting, to say the least.
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2003 GL MP62 supercharged / 2004 GLS stock
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