BOBthe4dH8r

iTrader: (1)

i finished swapping my 99 ls1 into my 86 3/4 ton siverado 4x4 and had little to no problems, but ive been daily driving it now for a month or so and ive noticed that when the efan turns on, via the pcm signal, the idle drops quite a bit and it SEEMS to have a slight loss in power.

it runs pretty good when its cold (considering its a 5600lb square hunk-a-steel on 35in tires and an old granny 4spd manual lol )

motor is completely stock (only has 69k mi)
pcm was sent to lt1swaps
i only have the low speed signal hooked up right now

any input would be appreciated thnx

ls1nova71

iTrader: (4)

All mine have done that. They have a slight drop in RPM when the fans come on. Never noticed any loos of engine power though. I wouldn't worry about it unless its loosing a lot of power.

BOBthe4dH8r

iTrader: (1)

im not really worried about the idle but im pretty sure that there is a power difference. and i think i read somewhere that if you have weak batt and your fans turn on it pulls some juice from your coils n stuff. is this true. i do have a cheap little napa battery but it doesnt act like a weak battery at least not while starting the motor.

can anything cause a noticable power loss when up to temp (200* ish) maybe i have a different problem. it runs fine. its just MUCH more rowdy when its cold and the fans are off

BOBthe4dH8r

iTrader: (1)

anybody got any other suggestions

BigEd_72455

iTrader: (7)

Get a DIGITAL volt meter from wal-mart. $20 range. hook it to the leads for the cigarette lighter, or raise the hood and hook them to the battery.

wait for the electric fans to kick on, and see what the voltage drop is.

What size wire is going from the alternator to the battery? If its smaller than an 8 gauge, you should upgrade it to larger. Have the battery itself checked. have the alternator tested while on the car. They can apply a load to it to see what the alternator is putting out. usually the reason for voltage drop all of a sudden is either fans going out, alternator is weakening, not big enough wire coming off alternator to support the load, or weak battery.

My ex-wife's focus had a bad habit of eating alternators. Until I added a second power wire from the alternator to the battery which was 4 gauge. Lights got brighter, car started faster. lots of improvements in the electrical system.

Also, make sure you have a good ground for the fans. and that that ground is going straight to the battery if possible with 12 gauge wire or larger. They dont look like it, but those efans pull a large amount of power while running. Usually 30+ amps.

One other thing, if you have the room... Check NAPA to see if they have a POWER UNIT battery, and look for the BIG ONE with top studs. Actual threaded studs. Those are some high power batteries. I have one in my S-10. Works perfectly all the time. Also has a high reserve capacity for longer times of just sitting and listening to a good song.

gofastwclass

iTrader: (2)

One of my cars started surging only when the fan would come on. Since I have HP Tuners, I started to log voltage and other a few things and realized the voltage dropped while the fan was running. I replaced the fan and all has been well.

As Big_Ed stated, power and grounds on these engines can't be stressed enough. This isn't an SBC with a carb, everything needs power or it simply won't go.

BOBthe4dH8r

iTrader: (1)

thanks guys. i really appreciate the help. i think im gunna start with wire size. i know that the wire off alt to batt doesnt actually go to the batt, i put it to the starter and its only a 10 maybe 8. the relay that runs the fan is a 25a Derale fan relay from summit. BUT the fans killed power and idle even when i was running them off a cheap toggle switch for the first few days so i think the relays fine. i will check all my grounds too. the fans are the stock fans out of my camaro with less than 70k miles on em so they should be good same with alt.

thanks guys. il post up what i find