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efi issues

2K views 7 replies 4 participants last post by  redheadedstranger 
#1 ·
well boys here is my problem, i went to the highlifter mud nationals this last weekend and after day one my brute started having issues with idling, like it was loading up in the middle of the powerband and when i would come to a stop if i let off the throttle it would just die, the only thing i changed was i ran a higher octane fuel in it, it is efi and im using the power commander BUT higher octane gas shouldnt affect the a/f mix like that should it?
 
#2 ·
What brand/kind of higher octane fuel did you use? It could have been oxygenated, which will definitely affect jetting.

Depending how high you went. It could have changed jetting some. Drain the tank, and put in your normal fuel and see how it run then. that would be the easiest test to eliminate that.

The power commander, does that replace your CDI? I would put the stock unit back on also. We've seen the after market units do weird things on the carbed units. So it wouldn't be surprising if they do the same on the EFI..
 
#3 ·
What brand/kind of higher octane fuel did you use? It could have been oxygenated, which will definitely affect jetting.

Depending how high you went. It could have changed jetting some. Drain the tank, and put in your normal fuel and see how it run then. that would be the easiest test to eliminate that.

The power commander, does that replace your CDI? I would put the stock unit back on also. We've seen the after market units do weird things on the carbed units. So it wouldn't be surprising if they do the same on the EFI..
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im not sure about the oxygenated part....but we tuned it with about a 95ish i would guess, and i was running straight 101, and as for the pcIII it doesnt replace the ecu, just piggybacks inline to the injectors, but on my bbk it wont even start without the extra fuel, although if someone doesnt have a fix soon im goin carbed hahaha
 
#4 ·
you should get it tuned on a dyno, a tuning center can tune the EFI with a custom advanced tune. meaning they adjust each cyinder by it self, to get max power.

what i think is wrong with your machine is if you had it tuned to run 87 oct and switched to 101 oct, you was running way to rich as higher OCT fuels burn slower then low oct fuel.

put it this way diesel fuel is 300 oct. this is why you need 20:1 or higher to burn it.

if you dont have the right cams and pistons, and A/F ratio to burn the higher oct fuel, for one your wasting your money on it and too, over time hurting the engine.

get it tuned up right and enjoy the power. if your EFI isnt throwing codes at you its failing.

also before i forget did you setup the throttle POS sensor when you hooked up the PC3. you PC3 coul be of setting , pull your plugs if they are black your way to rich, if they are white your way to lean.

a dyno will auto adjust the A/F ratio for peak performance.

call up dynojet and find the nearst dyno tuning center near you.
 
#5 ·
Sounded like he was running 92-94 octane. Then went to a 101 octane. That shouldn't be a big enough jump to make it go haywire.

It shouldn't harm the motor either. It'll actually run cleaner and little cooler. Granted you can go too high of an octane and experience negative effects.

Plus he said he has a big bore kit. So the higher octane still shouldn't be a prob.

Try the plug chop. Pull them and see what they look like.

Did you make a few runs in the mud? Maybe we could be looking at a mud/water issue. Airbox/filter all clean?
 
#6 ·
Did you make a few runs in the mud? Maybe we could be looking at a mud/water issue. Airbox/filter all clean?
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I'm thinking along those lines too. Did it act up as soon as you changed fuel, or did it happen later on?
 
#7 ·
could also be a blown head gasket, could be anything if you think of it, but i wouldnt say its the EFI system. unless i looked into everything else first, but i stand with having it dyno tuned for max performance. downloading maps, or going by the seat of the pants isnt going to make it perform to 100%.


also do a leak down test, check for leaking valves or piston rings.
 
#8 ·
i know its not in the motor itself unless its the valves out of adjustment a hair, motor was litterally built 3 weeks ago and dyno tuned, just not tuned perfect, soooo im looking at their map and its leaned out on the low end for some odd reason, and it happened about an hour or so after going up on octane, the dyno center i took it to didnt have a load cell or dual sniffers, the one i have an aptmnt at monday has both, hope that is the fix im looking for, oh and once i was up in the rpms the motor runs perfect on the 101 throttle response is perfect, thats why it was really giving me a headache about the low rpms being the issue
 
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