OBD II Scanner (Engine load at idle) [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: OBD II Scanner (Engine load at idle)


Mistral150
01-01-2010, 04:57 PM
After I bought my scanner, I looked at live data page and there was ENGINE LOAD % and mine was about at 25 % at idle and at 200. Is it too much or normal ?

I wounder if anyone here could compare this data with mine. I'm still trying to find the cause of low MPGs (10 mpg). Plugs changed (AC-DELCO Iridium). Thermostat changed (GM). Air filter ok.

Thanks for you time.

Chickenhawk
01-01-2010, 05:51 PM
Ignore that.

Look at the oxygen sensor data for sensor 1, bank 1. It should fluctuate rapidly above 0; from about 200 mV to 900 mV. What are your readings, and how fast are they changing?

Now check oxygen sensor 2. This is your downstream sensor, and the readings should be pretty solid, with few fluctuations. It should read close to 0. What is that reading and how fast is it changing?

Now look up your readings for short term fuel trim (STFT) and long term fuel trim (LTFT.) These readings will be expressed asa percentage and should be +/- less than 8%. The STFT should bounce a lot between +/-5%. The LTFT should be pretty steady and ideally will be near 0. What are your readings for STFT and LTFT?

Next, read the many threads here on mileage.

Nobody can say exactly what is wrong or whether anything is wrong because driving conditions and driving styles vary. But there are certain common causes of much poorer than normal mileage figures.

The funny thing is that we tell people to look for these things time after time, and for some reason, very few people actually come back to report their findings. I guess some people would rather just throw parts at the problem or hope maybe some mechanic will stumble across the answer (or combination of answers.)

The common causes of decreased mileage are:
- city versus highway driving
- driving style
- plugged cat
- bad thermostat
- lazy oxygen sensor
- worn or wrong type spark plugs
- winter gas
- bad fan clutch
- oil sludge buildup
- dirty throttle body
- changing tires to ones with a higher rolling resistance

(These are in rough order, from the most effect to the least.)

So let us know what your scan tool reads, what your mileage is and what you have already checked. Good luck and stick with it!:)

Mistral150
01-01-2010, 11:53 PM
Ignore that.

Look at the oxygen sensor data for sensor 1, bank 1. It should fluctuate rapidly above 0; from about 200 mV to 900 mV. What are your readings, and how fast are they changing?

Now check oxygen sensor 2. This is your downstream sensor, and the readings should be pretty solid, with few fluctuations. It should read close to 0. What is that reading and how fast is it changing?

Now look up your readings for short term fuel trim (STFT) and long term fuel trim (LTFT.) These readings will be expressed asa percentage and should be +/- less than 8%. The STFT should bounce a lot between +/-5%. The LTFT should be pretty steady and ideally will be near 0. What are your readings for STFT and LTFT?

Next, read the many threads here on mileage.

Nobody can say exactly what is wrong or whether anything is wrong because driving conditions and driving styles vary. But there are certain common causes of much poorer than normal mileage figures.

The funny thing is that we tell people to look for these things time after time, and for some reason, very few people actually come back to report their findings. I guess some people would rather just throw parts at the problem or hope maybe some mechanic will stumble across the answer (or combination of answers.)

The common causes of decreased mileage are:
- city versus highway driving
- driving style
- plugged cat
- bad thermostat
- lazy oxygen sensor
- worn or wrong type spark plugs
- winter gas
- bad fan clutch
- oil sludge buildup
- dirty throttle body
- changing tires to ones with a higher rolling resistance

(These are in rough order, from the most effect to the least.)

So let us know what your scan tool reads, what your mileage is and what you have already checked. Good luck and stick with it!:)

Ok !! I'll bring my results tomorrow.

Bought this TB 2003 it had 89000 KM so I knew I had to do the plugs, thermostat, tire inflated correctly, my driving is smooth, fan clutch ok, the throttle body has to be clean, air filter ok.

:thx

Chickenhawk
01-02-2010, 07:06 AM
You already made some good choices and you have your own scan tool, so you are pretty well equipped for almost anything that can go wrong in the next few years - with the help of this forum, of course.

Since you changed the plugs anyway, you might as well buy a new upstream oxygen sensor. Even if it is in perfect shape - and we'll know tomorrow when you bring us your scan tool readings - it should be replaced. If it happens to be the original one, they can almost weld themselves tight to the manifold after a few years, so it is good to get a fresh one in there anyway.

Since your mileage is WAY down, go through my list and see what you might have missed. Getting your cat checked is a simple process at any muffler shop. They will screw in a compression gauge into the hole that the front oxygen sensor fits in and measure the exhaust backpressure. (Anything over 4 psi is bad.)

Here's a tip: if you are half-thinking of getting an exhaust backpressure test done, buy the new O2 sensor but don't put it in until AFTER the test. Let THEM sweat with a breaker bar to get it out. (If you take it to a muffle shop, bring your new O2 sensor with you; they will LOVE you because it means that can simply snip off the wire and use a deep socket to get the old one out. The slotted oxygen sensor sockets will NOT hold the torque necessary to remove one when it is almost seized in place.)

In the summer, you should be able to easily get 600 kilometers on a tank of gas on the highway, and 500 with a mix of city and highway.

In the winter, with a little bit of 4wd, lots of idling in the city and lots of cold starts with winter-blended gas, you would be very lucky to get 350 kilometers on a tank.

Tis the nature of the beast.

Mistral150
01-02-2010, 10:01 AM
Ignore that.

Look at the oxygen sensor data for sensor 1, bank 1. It should fluctuate rapidly above 0; from about 200 mV to 900 mV. What are your readings, and how fast are they changing?

Now check oxygen sensor 2. This is your downstream sensor, and the readings should be pretty solid, with few fluctuations. It should read close to 0. What is that reading and how fast is it changing?

Now look up your readings for short term fuel trim (STFT) and long term fuel trim (LTFT.) These readings will be expressed asa percentage and should be +/- less than 8%. The STFT should bounce a lot between +/-5%. The LTFT should be pretty steady and ideally will be near 0. What are your readings for STFT and LTFT?


Do I check these on idle ??

Chickenhawk
01-02-2010, 02:51 PM
Yes, idle is fine.

Wait for it to warm up so that it runs in "closed loop" mode.

Mistral150
01-02-2010, 07:40 PM
There it is... I finally got my results from the scanner.
Recorded LIVE DATA from hot motor and running idle and based on 20 frame recording.

ECT: 203
STFT: -1.56% to 5.47%
LTFT: Steady -5,47%

O2 sensor Bank 1: 60 mv to 810 mv fluctuating up and down
O2 Sensor Bank 2: Pretty steady at +/- 700 mv but went down at 350 mv

Today I bought my throttle body cleaner and hope to clean it on sunday (it has to be done).

Other thing... I unplug the battery when I did the plugs and the scanner as

not finish the "EVAP" testing, how long it takes to finish or anyway to

stop the test ?

Tanks again for your support.

Chickenhawk
01-02-2010, 10:01 PM
Everything looks fine. It is maybe running a touch rich, which is why it is compensating with a very slight lean fuel trim.

Your coolant temp is a touch low, and that might be the reason.

Clean the throttle body, disconnect the battery while you do so and let us know if there is any improvement.

Don't worry about the "evap" test. It takes at least three cycles, with the coolant and OAT over a certain amount, and you have to be driving a certain distance before it even performs the test. If you drive a fair amount of miles to work, it could run several times a week. If you do nothing but short trips, it may not even run more than once a month in the winter.

Mistral150
01-02-2010, 10:47 PM
Your coolant temp is a touch low, and that might be the reason.


About the ECT... I changed the thermostat so it is brand new OEM and was woundering if US and CAN thermostat could have a difference in temperature ?

Everything looks fine. It is maybe running a touch rich, which is why it is compensating with a very slight lean fuel trim.

So I dont have to change O2 sensors ?

Thanks again. :thumbsup:

Chickenhawk
01-03-2010, 12:29 AM
If those readings for the front oxygen sensor are fluctuating rapidly, then no.

By rapidly, I mean up and down several times a second. (Or at least, as fast as your scan tool can renew the data.)

If there are several seconds between fluctuations, then yes, you need to change it.

Aren't scan tools wonderful? They can tell us so much of we know what to look for.

I wouldn't worry about your coolant temp. It is not bad. Keep an eye on your gauge and if someday it decides to read a hash mark on the cool side instead of the normal 12 o'clock position, then it is time to change the thermostat (again.)

Mistral150
01-03-2010, 12:39 PM
Today I cleaned mt throttle body with Canadian Tire Throttle body cleaner (Not Carb cleaner) and rubbed it with toothbrush and it was pretty easy to do. I broke the locking clip that retains the electrical connector to TB :worried:, I unpluged the battery for all the work time (45 min.).

I'll be back to bring the data from the scanner and MPG's after a full tank. I hope it has done something good. :hail:

:thx:thumbsup:

Mistral150
01-04-2010, 07:46 PM
There it is... I finally got my results from the scanner.
Recorded LIVE DATA from hot motor and running idle and based on 20 frame recording.

ECT: 203
STFT: -1.56% to 5.47%
LTFT: Steady -5,47%

O2 sensor Bank 1: 60 mv to 810 mv fluctuating up and down
O2 Sensor Bank 2: Pretty steady at +/- 700 mv but went down at 350 mv

Today I bought my throttle body cleaner and hope to clean it on sunday (it has to be done).

Here is the new data from scanner AFTER cleaning TB.

ECT: 203
STFT: -7.03% to 3.13%
LTFT: Steady -3.13%

O2 sensor Bank 1: 50 mv to 840 mv fluctuating up and down
O2 Sensor Bank 2: Pretty steady at +/- 740 mv with lite fluctuation

:undecided :thx

Mistral150
01-19-2010, 05:15 PM
I have my new results...

Went from 10 mpg to 13.5 MPG (Winter)...Thats a 3.5 mpg gain :thumbsup:

:thx

Kage_
01-19-2010, 11:58 PM
Not bad! What make/model scan tool are you using? I need to get one for my '04, but there are a ton of em ranging anywhere from $30 to more than I can afford.

Kage_

Chickenhawk
01-20-2010, 03:16 PM
There are essentially two types of so-called 'scan tools.' One is more properly called a code reader, because that's all it does; it reads (and often resets) trouble codes.

The other type (which is way more expensive) actually ties in to all the sensors in your vehicle and can read the data coming off them.

THIS is the one you want. Being able to read live data can go a LONG way to diagnosing emissions-control problems.

You can also buy an ABS scan tool that can read ABS trouble codes. (They are not cheap either.) They can't reset trouble codes, but can read them.

Scan tools that could read BOTH engine and ABS trouble codes were not allowed by law until very recently. The government didn't want home mechanics to be able to diagnose ABS problems so they mandated that scanners could only read engine codes. (This is why the Actron ABS code reader is not allowed to reset ABS codes.)

Now, there are some scan tools that do both engine and ABS codes, and can read live data from the engine. (Check out some of the Innova scan tools, for example.)

At the next level of scan tool is the tool that can CONTROL the engine. These are typically made by Genysis, Snap-On, Modus (same as the Snap-On) and GM (the famous and infinitely useful Tech 2.) They start at $2K and go way way up from there.

For most enthusiast owners, the live-data scan tools such as the Innova 3130 that I use is a good value. Here is a good comparison chart between the various tools:
http://www.canobd2.com/Products/Tools.aspx

awer25
01-20-2010, 04:41 PM
I bought this one (http://cgi.ebay.com/ebaymotors/ODB-II-Professional-Auto-Scanner-Tool-ODB2-ODBII-2_W0QQitemZ160394864382QQcmdZViewItemQQptZMotors_A utomotive_Tools?hash=item25584766fe) and it worked great. It's $65 + shipping and reads the computer's live data stream and also freeze frame data (a "snapshot" of the data stream when the trouble code was thrown). It doesn't do CAN though, which I think is necessary for '06+ or '07+ Trailvoys.

skoehlke
01-20-2010, 05:05 PM
Would Freeze Frame data work? A frined of mine has an Actron CP9175. Can I get the same info from that one?

awer25
01-20-2010, 05:22 PM
Would Freeze Frame data work? A frined of mine has an Actron CP9175. Can I get the same info from that one?

You can see the freeze data with that one, but you can't view the data stream. You need the CP9180 for that.

rbarrios
01-20-2010, 05:32 PM
this is also available for your laptop.
I dont know how it compares to those handheld units- but looking at the owners manual(online) it appears to also supply the data you mentioned below.

http://www.myscantool.com/

KNBlazer
01-20-2010, 07:33 PM
you clean the throttle body yet? and then disconnect your battery for 30 minutes.. ? what were your results...

Mistral150
01-20-2010, 07:57 PM
I did not see any improvement cleaning my TB, it was not very dirty.

Next thing I did this week end, is sea foam by the brake booster vacuum then put the rest in fuel tank and put a new air filter (Napa Gold) I'm waiting for the next fill up :coffee

:thx

longhorn262
03-10-2010, 11:36 PM
This is what my sensors or reading. Im thinking the cause for my bad mpg is a bad thermostat running pretty cool. Is the LTFT supposed to jump around like that?

longhorn262
03-11-2010, 09:13 PM
anyone?

cgallo
03-11-2010, 11:30 PM
anyone?

I think the readings are good ans acceptable..there are somo STFT High but I think is a normal correction if you qit your foof of you gas pedal...for me if you have a problem with MPG, you need to search another thing...Mine only gets 11 or 12 MPG in City with alot of stops and Highway 15 mpg:eek:

Super 88
03-12-2010, 11:55 AM
anyone?


I would say your temps are too low. 179 - 183. The thermostat rated temp is the temp it starts to open (usually around 190 - 195) so the vehicle should run at LEAST that hot - usually somewhere around 200 - 205.

willisJ
02-15-2011, 03:42 PM
Ignore that.

Look at the oxygen sensor data for sensor 1, bank 1. It should fluctuate rapidly above 0; from about 200 mV to 900 mV. What are your readings, and how fast are they changing?

Now check oxygen sensor 2. This is your downstream sensor, and the readings should be pretty solid, with few fluctuations. It should read close to 0. What is that reading and how fast is it changing?

Now look up your readings for short term fuel trim (STFT) and long term fuel trim (LTFT.) These readings will be expressed asa percentage and should be +/- less than 8%. The STFT should bounce a lot between +/-5%. The LTFT should be pretty steady and ideally will be near 0. What are your readings for STFT and LTFT?

question if anybody knows.. i'm trying to track down some same mileage issues with my envoy using torque (on my android).

the upstream oxygen sensor should be bank 1 sensor 1 as above, the downstream sensor is bank 1 sensor 2? or bank 2 sensor 1 (or sensor 2)?.. I am going to try bank 1 sensor 2 first and see what that says, anybody know for sure?

also, stft and ltft.. looking thru the torque forums and a couple other places, these should equate to fuel trim bank 1 sensor 1 and fuel trim bank 1 sensor 2.. i think those are correct but has anyone else used this app to check??

thanks

willisJ
02-15-2011, 05:47 PM
question if anybody knows.. i'm trying to track down some same mileage issues with my envoy using torque (on my android).

the upstream oxygen sensor should be bank 1 sensor 1 as above, the downstream sensor is bank 1 sensor 2? or bank 2 sensor 1 (or sensor 2)?.. I am going to try bank 1 sensor 2 first and see what that says, anybody know for sure?

also, stft and ltft.. looking thru the torque forums and a couple other places, these should equate to fuel trim bank 1 sensor 1 and fuel trim bank 1 sensor 2.. i think those are correct but has anyone else used this app to check??

thanks

annnnd next time i'll look at available sensors thru torque when it's all plugged in and running instead. all the bank 2 and bank 3 crap disappeared bc we don't have them lol..

ok so..

o2 bank1 sensor1 jumps all over the place. it was measuring in volts instead of millivolts but the theory is the same.. jumped consistently between .1 and .9 around 2-4 times a second

o2 bank1 sensor2 i was hoping was the rear o2 sensor, and now i'm hoping it's not. it stayed steadier than sensor1, but was nowhere near zero. it stayed right around .7, .6, .8, etc. when i was in stopped traffic for a minute or two it did drop to 0 (but so was sensor1) but when i started going again it jumped right back up to .7ish

stft was also as expected.. +/-5%.. noticed a spike here or there to -8 or +10 but the majority of the time was quickly jumping around the lower numbers

ltft i thought was bank1 sensor2, but again now i hope not. it did stay rock steady, however it stayed rock steady at 99.2%


any thoughts?? doing plugs tonight or tomorrow, also gonna clean the tb while i'm in there, just did the thermo and temp sensor (which lead to all of this bc i did the thermo/sensor and my mileage dropped while coolant temps increased)

Fishsticks
02-15-2011, 07:17 PM
annnnd next time i'll look at available sensors thru torque when it's all plugged in and running instead. all the bank 2 and bank 3 crap disappeared bc we don't have them lol..

ok so..

o2 bank1 sensor1 jumps all over the place. it was measuring in volts instead of millivolts but the theory is the same.. jumped consistently between .1 and .9 around 2-4 times a second

o2 bank1 sensor2 i was hoping was the rear o2 sensor, and now i'm hoping it's not. it stayed steadier than sensor1, but was nowhere near zero. it stayed right around .7, .6, .8, etc. when i was in stopped traffic for a minute or two it did drop to 0 (but so was sensor1) but when i started going again it jumped right back up to .7ish

stft was also as expected.. +/-5%.. noticed a spike here or there to -8 or +10 but the majority of the time was quickly jumping around the lower numbers

ltft i thought was bank1 sensor2, but again now i hope not. it did stay rock steady, however it stayed rock steady at 99.2%


any thoughts?? doing plugs tonight or tomorrow, also gonna clean the tb while i'm in there, just did the thermo and temp sensor (which lead to all of this bc i did the thermo/sensor and my mileage dropped while coolant temps increased)

I use Torque as well.

My fuel trims looks similar to yours, with 1x2 being locked a 99.2%, I suspect this is a math error on the extended PID but I haven't really messed with it.

I'm reasonably sure that O2 1x2 is the upstream O2 sensor and 1x1 is the downstream. My 1x2 has always moved faster and with a greater range than my 1x1. My upstream O2 sensor has less than 10K miles on it.

My coolant temp sits between sits around 195* give or take, depending on driving/stopped status.

willisJ
02-15-2011, 07:29 PM
I use Torque as well.

My fuel trims looks similar to yours, with 1x2 being locked a 99.2%, I suspect this is a math error on the extended PID but I haven't really messed with it.

I'm reasonably sure that O2 1x2 is the upstream O2 sensor and 1x1 is the downstream. My 1x2 has always moved faster and with a greater range than my 1x1. My upstream O2 sensor has less than 10K miles on it.

My coolant temp sits between sits around 195* give or take, depending on driving/stopped status.

good to know on the fuel trim.. i saw a couple posts on the torque forums about ltft as well but nobody answered them.

and really, your o2 1x2 moves quicker than 1x1? mine is completely opposite, and i thought from previous posts that 1x1 is definitely the upstream.

who knows..