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Discussion Starter #1
Guys,

'01 Frontier S/C 4wd Crew Cab with AUTO tranny

I've owned my truck for 4 years - and just the other day it had go like I've never seen before. Then the next tank of gas the power disappeared again. So I started trouble shooting and need a bit of help.

Problem: 1 or 2 runs from warmup will result in the following:
* Strong boost w/ immediate throttle respose, rushing air sound with good pull to max
RPM (6100 shift 1 to 2 and 2 to 3). Auto Tranny.

* After 1 or two runs - there is a brief moment of boost then the system drops back to
a very lathargic setting (power loss) and the following occurs:

After power loss:
* poor throttle response (can't break the tires loose if your life depended on it), supercharger whines excessively (no rushing air sound), poor shift quality (hunts for gears), engine starved for air at ~4700 rpm - max engine speed is ~5100 - 5300. You need to release the gas pedal for the auto tranny to shift into next gear (seems it hasn't reached a programmed step in the shift logic). NOTE: This is the way it has always run - so I never realized what I was missing!

Things I've done:

Fuel: Always run 93 octane as recommended. To rule out fuel I filled fresh with 93 octane and added MMTE Octane Boost (race formula). Fuel should be around 103 octane right now. Thought to do this to eliminate spark knock.
Observation: No Change - 1 to 2 runs then back to normal (no power)

next: Air - new K&N air filter (not the FIPK).
Result - No change

3: Cold Start Solenoid: Seems to function properly - hold blow off valve closed when cold - open when hot.

4. Supercharger vacuum solenoid bypass valve: Seems to operate fine - normally open when hot (spring return on supercharger). will briefly close when revving under no - load condition. I assume that means under full load it would stay closed.


Where do i go from here??? I'm thinking a MAP problem, or Knock Sensor?? or some other computer controlled vacuum drop? I need help - Nissan dealer just keeps blaming it on me not using 91 minimum octane fuel - and that has never been the case! There are no active engine codes (don't have a deep scanner though - just codes that would throw off the SVC ENG light).

I want the power back!

Thanks
 

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Discussion Starter #2
Well - got to the root of the boost drop. I finally convinced the dealer I always use 93 octane and they took a look at the system. Found the following problems: 1) vacuum solenoid bad 2) vacuum blow off valve bad 3) knock sensor bad.

Supercharger is now supercharging for the first time in the 4 years I've owned the truck - WOW what a difference. Darned glad it was a Nissan Certified - all the work was done under warranty.

Now I can look at a smaller pulley:)
 
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