Symon623

'03 LQ4 in a 85 Toyota pickup rock crawler...... Jims performance computer and harness clean up. Originally drive by wire converted to drive by cable..

Problem: The more accessories I run, cooling fan, headlights, wipers, heater fan etc, the worse it runs at idle, seems to be better off idle but jerks when the cooling fan cycles on and pulls a load on the alternator..... Unplug the alternator and it runs great accross the band.....

New alternator, computer. Bypassed the computer controlled exciter wire with a key on source through a light bulb to the B post in the alternator plug, larger than stock wiring off the charge post of the alternator. All had no improvement.

No charging system related codes. I have P0102 and P1336 codes, both of which shouldnt effect this problem.

Anyone have anything?

Thanks

rotor vs. piston

iTrader: (3)

Only thing I can come up with is that you may need more/better grounding and/or a larger reserve capacity battery. More so just the grounds.

ls1_chevelle

iTrader: (9)

x2 on grounds. Over ground it all!

and what size is your charge lead off the alt?

Symon623

It runs better on the batteries.....yes 2 of them..... Optima red tops.

Likin the ground idea

Symon623

#8 from the charge post to a common post on the drivers inner fenderwell, #1 from the drivers fenderwell to the starter post, #0 from the starter post to the batteries in the back of the truck..... 14.1 volts at the charge post of the alternator, 13.8 volts at the batteries at idle when no accessories are on.

ls1_chevelle

iTrader: (9)

This is similar to how I have mine wired and I have little notice when the fans are on. However... I am wondering if you grabbed all your 12 volt from the battery and ran a larger lead off the alt back to the batteries. So your accessories draw directly from the batteries, no chance drawing from the alt. Just a thought

Pop N Wood

iTrader: (1)

Believe it or not I have seen similar gremlins caused by dirty battery posts. Every time I hit the turn signals the engine would cut out for a second.

Where do you have your engine computer drawing power from? Try hooking a voltmeter at the power wire going into the computer. Make sure that stays near 14V. Also I would have gone at least 4 gauge from the alternator to your fenderwell common post. That wire is actually more important than the wire heading back to the batteries. When the engine is running the wire to the batteries should only be carrying a few amps but the one coming out of the alt will be carrying the full rated capacity (140 amps?). I wouldn't run the alt wire to the batteries for the same reason. The way you have it hook up is ideal.

I would also run a wire from the battery negative post straight to the block using the same size wire that you used for the positive lug. Lots of people ground the battery through the frame but don't run starter current through body panels.

ls1_chevelle

iTrader: (9)

Many people ground directly from battery to frame. Just make sure the frame is grounded battery, frame grounded to the engine, engine grounded to body.

Symon623

OK, I went home last night and removed the 3 ground wires fron teh back of the block (factory location) and checked them for cracks or broken wires. They looked good but in my application they are a real PITA to access so I moved them to the back of the drivers side head along with the wire mesh ground strap that came with the motor. I hooked the other end of the mesh strap to the cab on the fire wall.......

Went for a test drive and seems to be workng great now..... all about the grounds.... Thanks for the help guys

On a complete side note, another issue I've been fighting is a random hi idle..... usually after driving to get it good and warm. IAC has been replaced, scan tool says that % of throttle under normal idle is 0-0.4% idling at 700 RPM. when the idle is up the scan tool says the 5 of throttle is 8% at 1400 RPM and 12% at 1700 RPM...... any guesses?

Symon623

PCM constant hot goes to the same common post on the fenderwell.... Key on hot gos to the Toyota fuse for "ignition" and seems to be delivering clean, constant voltage.

Understand the alternator charge wire..... I am running the smaller alternator for hood clearence purposes..... th 140 alternator is ¾" taller and I needed the help..... Anyway..... Batteries are grounded to the frame with #0 cable, then I have another #0 cable from the frame to the engine.... Just added the "mesh" ground strap between the engine and the cab and hoping, or so far have fixed that issue.

Symon623

Here's the rig I have the motor in and what I do with it from last Saturday;

http://youtu.be/jmjWtevHYhE

Old Geezer

iTrader: (3)

Check for volt drop when starting, using the frame as a ground source. See what you get.

ls1_chevelle

iTrader: (9)

Yea these LS engines require perfect grounding to work with no flaws. Glad that is sorted out.

Stock engine or is there a cam in it? pcv acting up? if it is leaking it would cause a vac leak which will cause idle problems.

Symon623

It is stock..... it idles nice a smooth now. 700 in or out of gear...... Gonna do the crank re-learn procedure as soon as my buddy gets the right scan tool for it....... I should have known about the grounds since I went through all this on my Dodge CTD......

bczee

iTrader: (12)

I was told my a instructor many, many years ago.. 90% of electrical problems are ground related .. and now with the new engine and cars/truck.. that demand for more electrical requirements and loads.. good clean power supply and grounds are a must !

Glad to see you got it resolved ! Been watching you guys LOL.. These are the type of threads I like to see on this forum.. problems with good suggestion and fixes..

BC

Symon623

So far so good...... did a good old fashioned cleaning of the throttle body and the IAC port and the idle has been pretty good for now..... I will be driving and wheelin it all weekend so I will update on Monday after a few more heat cycles.... Thanks again for all the help guys

Symon623

Had it up in a little snow this weekend and it ran great...... power and torque are fun and driveability was nice and fun.....

I did realize that this rig now has the largest displacement engine of the 3 vehicles I own and it is STILL the slowest of the 3..... WTF?

bczee

iTrader: (12)

Havw you had the engine Dyno Tuned ?... could be any number if of tuning issue.

But then again.. depends on where you are going.. being fast doesn't always get to over the Rock.. But fast makes it a lot more Fun ! LOL

Symon623

I was jokin, it is fast, or quick, gets along great even though I'm pushin 37" tires and a 5000 pound truck..... i was merely having a laugh that is is slower than my other 2 vehicles listed in my sig line..... Some think I have issues.

Back to the 1st hijack topic though...... my hi idle came back last night after I drove it about 10 miles, shut it off for 10 minutes, started and was fine, drove 8 miles, shut it off for 20 minutes then started it and it was up around 1400 then back down to 1000 but never settled in to its normal 700......

Any ideas?

ls1_chevelle

iTrader: (9)

just had a thought... originally was the engine a mechanical cooling fan? I cant remember if the idle rpm increases when the fan clutch locks up when the engine starts running above normal temp(dictated by the water temp sensor and ecu).

Your electric cooling fans should be able to control the temp though, but no need to increase the engine rpm.

again I can't remember if my thoughts are correct or not lol