Today

[DeeJayy]

So today I pulled my temp sensor wire out of the sensor and I started the car and the fans turned on full blast the whole time but I put it in drive and it jumped hard. I plugged it back in and it didn't do it anymore. Any thoughts?

[03glgold]

Ghosts

[RalphP]

Thoughts?

That it was doing what it was supposed to do?

Fans on high in case the car's overheated, and run it rich which would make it jumpy.

RwP

[ndkpyro]

Had this happen on my 01 malibu the computer gets crazy temp readings when there is a open and jacks up trans pressure

[AleroB888]

Yeah, my first thought was "Why did you do that?" lol

[DeeJayy]

Originally Posted by RalphP

Thoughts?

That it was doing what it was supposed to do?

Fans on high in case the car's overheated, and run it rich which would make it jumpy.

RwP

Jumpy only when I shift it to drive. Like a hard thud. I think its just the computer not recognizing that nothing is connected there.

[DeeJayy]

Originally Posted by AleroB888

Yeah, my first thought was "Why did you do that?" lol

To see if my fans would kick onto high.

[RalphP]

Idle would also be up higher - which would make it more of a "thud" when you shift it in.

Idle is up higher because the mix is richer.

Why were you driving it with the sensor unplugged is the next question. It doesn't need to be driven to verify the fans are on.

Also, why were you checking this? Have you picked up a reader or scan tool that allows you to see what temp the ECU is seeing yet?

RwP

[03glgold]

maybe he doesn't have access to said scan tool and really can't afford one, so before going through the extra expense he wanted to take a basic troubleshooting approach to make sure the fan plate still turned on

[RalphP]

*shrug* OBDII/Bluetooth adapter can be had for $30 or so from Amazon, Torque Free is, well, free, only requires an Android device with Bluetooth (amazingly, such cell phones can be had for free on 2 year contracts!)

I can't see doing much without such like myself.

But eh. I'm olde skool, prefer to see the numbers instead of just jacking around.

(I still don't know why he was trying to drive it ... disconnect the ECT to check the fan, sure. Plug it right back in, though, because the ECU is going to do some really funky stuff to protect the motor from the boundary condition he emulated.)

RwP

[03glgold]

I do agree with you on the driving part...I wonder if he is having computer problems though and that would possibly explain the fans as well as the fact that his gauges now only come on when they want to, and sometimes it doesn't want to start...I agree with you that numbers are good to have, I didn't even know they made obdII/ bluetooth adapters, and that free phone isn't free because you have a monthly bill...not everybody has a 2 year smart phone contract...I have a prepaid pos phone because it gets done what I need it to do

[RalphP]

Well, the "free on a 2 year contract" - I would pay the same contract price each month if the phone was $0 up front or $599.95 up front, so no additional (a better phrase than "free", true.)

I'm betting with the intermittents he's got a problem with the ignition switch, or the ignition switch contacts, but that's just a SWAG from previous experience on these parts from GM (specifically in Malibus, Cutlasses, Grand Ams, and the few Aleros my nephew got into the yard back when he owned one ... )

As to the Android device - they also make units for iDevices for the Apple fanbois and a lot of Android tablets support WiFi, so it's not such a stretch that someone may own a tablet that will also work. Torque doesn't work for an iDevice, however.

I also have a nice USB / OBDII device I used on the Malibu until I found the Bluetooth adapter ... it was more like $50, but still, no additional if you already own a Macintosh or Windows laptop.

RwP

[MilzyZ34]

idle speed would be 1200 instead of 675, but there are far worse things from doing that ...

commanded air-fuel at wide open would be 9:1 (black smoke, risk of leaking fuel past rings into engine = BOOM)

timing advance gets a +14 degree adder at -40, to help warm up the car. if the car is already warm, +14 degrees on top of the commanded timing table = BOOM

in other words, don't do that.

[MilzyZ34]

stock fan settings are set to come on only above around 220 degrees or hotter. high speeds don't come on until 230 or so. if you want them to come on sooner to help keep the car cooler, this is one of the features we offer on our pcm's.

[a.graham52]

Originally Posted by MilzyZ34

idle speed would be 1200 instead of 675, but there are far worse things from doing that ...

commanded air-fuel at wide open would be 9:1 (black smoke, risk of leaking fuel past rings into engine = BOOM)

timing advance gets a +14 degree adder at -40, to help warm up the car. if the car is already warm, +14 degrees on top of the commanded timing table = BOOM

in other words, don't do that.

i would think that with the coolant temp sensor unplugged the computer should see a fault and put itself in "limp-home" which includes things like max line pressures in the trans (causes the hard thud), and also the fans to come on all the time. i dont belive the computer would allow things to get out of hand with timing and fuel trims because of the "fault" in the system. it would be different if somone programmed the computer to think it was normal.

[MilzyZ34]

when it's unplugged, it defaults to -40 degrees F, which puts it into the tables at that temp. there is no limp-mode for ECT that I know of. There are "limp-modes" when the pcm declares abuse for various reasons, if you exceed speed limiters, or if there is a problem with the maf or O2 sensor, and the vehicle resorts back to speed density. There are some different tables for the engine and trans if the sensors show they are too hot, and then measures are taken to reduce power or shift easier, but as far as low temps go, I don't see anything like that. people often think that every sensor will have a code if it malfunctions, and this is simply not true.

now as for what I said, that's true that if you run it wide-open throttle at "negative 40 degrees" it will command afr to be 9:1. 9:1 is so rich though that I'm not sure even 14 degrees more timing would blow it up now that I think about it. Running 9:1 would probably drop a 140whp stock alero down to about 70whp to give you an idea how much power that drops.

[WhiteV6]

It will throw a code on the 2nd error. Also, you have to put the CTS and AIT on a switch with resistors to give a usable reading, and throw them right before you floor it so that the computer doesn't have time to react and change the fueling beforehand. Trial and error are necessary to find the best settings.

[Redog]

Originally Posted by AleroB888

Yeah, my first thought was "Why did you do that?" lol

Me too

Originally Posted by DeeJayy

To see if my fans would kick onto high.

You get the same result when you turn on the AC full blast. If the fans don't kick on with the AC on, you have a problem.

Redog almost overheated this week. first day it's in the high 80's here, AC on full blast, stop and go traffic because some dumb eff doesn't know what a green light means, and I get the warning chimes. Temp gauge is half way between red line and 3/4.

Windows down, heat on full blast, car started to cool down a bit. Take another route and constantly moving dropped temp too.

One of the wires on my fan switch broke off, thus only powering one fan. Fans back to stock until I can rewire them

[AleroB888]

lol

You know, I understood this stuff pretty well before I read this thread. Now I'm totally confused