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L32 3.4 wierd MPG


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#1 yoheer

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Posted 29 September 2020 - 12:15 PM

Hello. I need some help with log analyz. I'm trying to sort out what is wrong with the car, but can find nothing. My friend has a 95 firebird with L32 3.4 engine, automatic.
The car runs good, but MPG is awful for this engine. It is about 11 MPG.
New o2s, tps, fuel pump, injectors installed. No check engine light present. The car is stock.
We've collected logs and have a CSV file. Everything seems to be okay. I don't like MAP readings, they are 1.5V at idle, but Alldata says thats okay.
Can anybody take a look at the Log file? 
Thanx in advance. We are stumped and do not know how to solve the problem.

Logs made with scan9495 v6

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Edited by yoheer, 29 September 2020 - 12:17 PM.


#2 Injuneer

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Posted 29 September 2020 - 01:13 PM

I looked at the log on my iPad and it seems like the further to the right you look, the actual data is offset several columns from the column labels in the top row.

 

Maybe it will look better on my Windows laptop, using Excel.


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 yoheer

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Posted 29 September 2020 - 11:51 PM

Edited

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#4 Injuneer

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Posted 30 September 2020 - 07:45 AM

The .xlxs version is still a bit of a problem.  The first version had about 12 unlabeled columns on the right side, apparently dropping out column labels randomly.   Comparing the two files, the problem is due to the European use of the "," in place of the decimal point ".".  As a result, a number like 25.56 which the .csv file treats as a single entry, and gives it its own column, shows up as 25 , 56 in three different columns.      I think that will complicate my mathematical analysis.

 

I don't know enough about the formatting of Scan9495 to know if that can be changed.   I'll ask

 

@GaryDoug

 

to see if he can explain what needs to be done.

 

What is your concern about MAP sensor voltage?  The important thing is what the PCM converts that voltage to in kPa.  The idle MAP is about 40 kPa, which is indicating a vacuum (MAP - Barometer) of about 62 kPa (18.4 "Hg).  Maybe a bit low on vacuum, but not unheard of.



#5 GaryDoug

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Posted 30 September 2020 - 08:10 AM

There are two ways to fix the scan log file problem. The cause is that in Europe and some other countries, the comma is used in place of our period (dot) as the decimal point in numbers. To make the log file correct, you have to change that to a period/dot.

 

1. In the pc setup, change to US format

 

or better....

 

2. In the setup just change the comma to a period (dot).

 

You can change it back after the scan is done if you like.

 

In the Windows search box, type "Region". Click on "Region Settings". Click on "Additional time, date and regional settings" at the upper right. Click on "Change data, time or number formats". Click on "Additional settings". Change the decimal symbol to a period. Click on "OK"

 

 

 

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gallery_14511_2130_2884.jpg
1998 Trans Am - LS1/A4 - all stock - one owner - driven daily - Scan9495 author


#6 yoheer

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Posted 30 September 2020 - 08:26 AM

Thank you. I'll ask him to do this

#7 ZumpTA

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Posted 03 October 2020 - 06:50 AM

Are you using fuel blended with ethanol?


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#8 yoheer

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Posted 21 October 2020 - 04:54 AM

There is no such fuel in here

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#9 Injuneer

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Posted 21 October 2020 - 08:48 AM

Downloaded, looks useable.  I do have to familiarize myself with the 3.4L V6 data.... I don't get many of these to look at.  May take me a bit more time than usual.

 

The very last column is labeled "NoCamSignal" and if that is an indication of whether the ECM is receiving the cam position sensor data, it appears that it is cutting in and out.  I'll need to look through the factory service manual for the significance of this.   If "1" = no cam signal, the signal is missing 36% of the time.

 

Does the air conditioning work?  There is an indication that there is an "AC Request", but all the other data - clutch, feedback, pressure, temp - appears the A/C is not working.  If there's no A/C I can just hide all those columns to simplify the data.

 

 

 

 



#10 GaryDoug

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Posted 21 October 2020 - 09:04 AM

Downloaded, looks useable.  I do have to familiarize myself with the 3.4L V6 data.... I don't get many of these to look at.  May take me a bit more time than usual.

 

The very last column is labeled "NoCamSignal" and if that is an indication of whether the ECM is receiving the cam position sensor data, it appears that it is cutting in and out.  I'll need to look through the factory service manual for the significance of this.   If "1" = no cam signal, the signal is missing 36% of the time.

 

Does the air conditioning work?  There is an indication that there is an "AC Request", but all the other data - clutch, feedback, pressure, temp - appears the A/C is not working.  If there's no A/C I can just hide all those columns to simplify the data.

 

 

 

 

I think you can ignore the "cam signal missing" / "NoCamSignal" item unless it is on constantly. If I am remembering correctly, that normally flashes on and off. Staying on all the time could indicate a fault.


gallery_14511_2130_2884.jpg
1998 Trans Am - LS1/A4 - all stock - one owner - driven daily - Scan9495 author


#11 Injuneer

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Posted 21 October 2020 - 12:16 PM

OK.

 

Thx



#12 yoheer

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Posted 22 October 2020 - 01:23 AM

A/c is not deletet, but it is empty, no refrigirant



#13 Injuneer

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Posted 4 weeks ago

Few questions:

 

1. What brand are the O2 sensors?  The 3.4L has 1-wire (unheated) sensors, that can be very sensitive to operating temperature.

 

2. Why are you concerned about the 1.5 volt MAP reading?  The intake manifold vacuum at idle averages 64.8 kPa (19.2"Hg), which is acceptable.  You can calculate intake manifold vacuum by subtracting MAP (average = 39.6 kPA @ 1.55 volts) from BAROMETER (104.4 kPa).  A bit high for barometer.  What is the elevation above sea level where your friend lives?

 

3. What is the condition of the EVAP system - carbon canister in driver side rear fender to purge solenoid on engine)?  Possible source of a vacuum leak.

 

4. PCM runs in speed-density.  Critical inputs used to calculate mass air flow are RPM, MAP, IAT, and CLT.  The readings from these sensors seems rational.  For example at idle, RPM ranges from 710 - 904 RPM, MAP from 37.3 - 44.3 kPA (possibly indicates a rough idle/misfire), IAT 80 - 81degF, CLT steady at 215degF.

 

5. Were the changes you listed ("New o2s, tps, fuel pump, injectors") replaced in an attempt to solve the poor fuel economy?  Did any of them make a significant difference?  Have you checked the fuel pressure?  Are the injectors a good quality part - there are some very inexpensive Chinese counterfeits that are terrible)?

 

So far, the thing that puzzles me is the fact the long term fuel trims (LTFT) seem to drift up and down at random.  I'm looking for a correlation to something like duty cycle on the EVAP and EGR systems.



#14 yoheer

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Posted 4 weeks ago

1. O2 were in delco boxes, but they look like bosch
2. 295ft above sea
3.evsp seem to be okay
4. Dunno why it is in speed density
5.you,re right. Nothing made any effect. Pressure is okay. Injectors are gb remanufacturing
I can easily disable evap and egr in ecu

#15 Injuneer

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Posted 4 weeks ago

Did you check the EVAP vacuum line from the purge solenoid to the intake for leaks?  Did you check the EVAP purge solenoid for being stuck open?  How about the line from the purge solenoid to the canister?  There is evidence the ECM reads the engine as running rich under most conditions, and is reducing injector pulse width to reduce fuel, using the long term fuel trims.  But that is not always the case.  Under some driving conditions, for any specific fuel trim cell, the ECM drifts around between adding fuel and subtracting fuel.  That's when it becomes important to start looking for a cause, like malfunctions in systems like EVAP and EGR.

Ditto with EGR.  The problem is not that the ECM activates it.  The problem is leaks, valve stuck, etc..

 

It's programmed to run in speed-density.  I only mentioned “speed-density” because I was not aware if you knew that it was how the fuel demand was calculated, because the engine does not have a mass air flow sensor.  Hence, the importance of accurate sensor input from the MAP and IAT sensors in particular.  But I don't see any issues with those inputs.

 

I'll keep looking, but so far there is no obvious problem.



#16 yoheer

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Posted 4 weeks ago

Will check and report, thanx




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