Failed emissions

[Burned]

Hi,

I have a 1997 S10 4.3L that failed its emission test on Hydrocarbon and Oxides of nitrogen. It has a misfire and the oil smells like gas. I did a compression test and vacuum test, and both seemed fine.

Here is the data from my latest OBD2 scan:

OBD-II Diagnostic Report

System Status (Mode 01)
Trouble Codes
MIL Status Off
Number of DTCs 0
Continuous Monitoring tests
Misfire Supported Complete
Fuel System Supported Complete
Comprehensive Components Supported Complete
non-Continuous Monitoring tests
Catalyst Supported Not Complete
Heated Catalyst Not Supported
Evaporative System Supported Not Complete
Secondary Air System Not Supported
A/C System Refrigerant Not Supported
Oxygen Sensor Not Supported
Oxygen Sensor Heater Supported Complete
EGR System Supported Not Complete
Fuel System Status
Fuel System 1 Status open loop
Fuel System 2 Status open loop
Diagnostic Trouble Codes (Mode 03, 07, 0A)
Description
Stored Diagnostic Trouble Codes (DTC) (Mode 03)
No Trouble Codes
Pending Diagnostic Trouble Codes (DTC) (Mode 07)
No Trouble Codes
Permanent Diagnostic Trouble Codes (DTC) (Mode 0A)
No Trouble Codes

Monitored Test Results (Mode 06)
Description Value Min Max Units Result
TID $02, CID $04 - Values defined by manufacturer 0 0 Pass
TID $02, CID $16 - Values defined by manufacturer 0 0 Pass
TID $02, CID $26 - Values defined by manufacturer 0 0 Pass
TID $02, CID $36 - Values defined by manufacturer 0 0 Pass
TID $02, CID $46 - Values defined by manufacturer 0 0 Pass
TID $02, CID $10 - Values defined by manufacturer 0 0 Pass
TID $02, CID $20 - Values defined by manufacturer 0 0 Pass
TID $02, CID $30 - Values defined by manufacturer 0 0 Pass
TID $02, CID $40 - Values defined by manufacturer 0 0 Pass
TID $02, CID $12 - Values defined by manufacturer 0 0 Pass
TID $02, CID $11 - Values defined by manufacturer 0 0 Pass
TID $02, CID $21 - Values defined by manufacturer 0 0 Pass
TID $02, CID $31 - Values defined by manufacturer 0 0 Pass
TID $04, CID $20 - Values defined by manufacturer 32768 32767 Fail
TID $06, CID $35 - Values defined by manufacturer 24 88 Pass
TID $06, CID $41 - Values defined by manufacturer 29 105 Pass
TID $06, CID $47 - Values defined by manufacturer 36 213 Pass
TID $06, CID $55 - Values defined by manufacturer 24 88 Pass
TID $07, CID $0C - Values defined by manufacturer 32768 0 Fail
TID $07, CID $0D - Values defined by manufacturer 32768 0 Fail

Live Data (Mode 01)
Description Value Units Min Average Max
03 - Fuel System Status
Fuel System 1 open loop - 1.00 1.00 1.00
Fuel System 2 open loop - 1.00 1.00 1.00
04 - Calculated Load Value 2 % 1.96 2.21 5.88
05 - Engine Coolant Temperature 48 °C 48.00 48.80 50.00
06 - Short Term Fuel Trim - Bank 1 -7.8 % -9.38 -3.42 -0.78
07 - Long Term Fuel Trim - Bank 1 0.0 % 0.00 0.00 0.00
08 - Short Term Fuel Trim - Bank 2 -7.0 % -12.50 -4.86 -0.78
09 - Long Term Fuel Trim - Bank 2 0.0 % 0.00 0.00 0.00
0B - Intake Manifold Absolute Pressure 32 kPa 22.00 30.80 32.00
0C - Engine RPM 694 rpm 639.75 728.36 1575.00
0D - Vehicle Speed 0 km/h 0.00 0.00 0.00
0E - Ignition Timing Advance for #1 Cylinder 20 ° 18.50 21.30 26.00
0F - Intake Air Temperature 39 °C 39.00 39.60 42.00
10 - Air Flow Rate 5.37 g/s 5.13 5.49 7.84
11 - Absolute Throttle Position 0.0 % 0.00 0.00 0.00
14 - Bank 1 - Sensor 1
Oxygen Sensor Output Voltage 0.525 V 0.11 0.72 1.02
Short Term Fuel Trim -7.8 % -9.37 -3.36 -1.56
15 - Bank 1 - Sensor 2
Oxygen Sensor Output Voltage 0.130 V 0.13 0.68 1.03
Short Term Fuel Trim 99.2 % 99.21 99.21 99.21
16 - Bank 1 - Sensor 3
Oxygen Sensor Output Voltage 0.080 V 0.07 0.63 1.02
Short Term Fuel Trim 99.2 % 99.21 99.21 99.21
18 - Bank 2 - Sensor 1
Oxygen Sensor Output Voltage 0.205 V 0.12 0.70 1.01
Short Term Fuel Trim -7.8 % -12.50 -4.86 -2.34
1E - Power Take Off Status OFF - 0.00 0.00 0.00

[mwebb]

at 694 rpm air flow = 5.37 gm/s
too high - these have a MAF sensor ? i thought they were speed density ?
if speed density , intake vacuum is too low
if MAF it would be a digital MAF .

STFT = -8% and LTFT = 0%

whenever i see a vortech engine subtracting fuel , i think INJECTOR
those injector assemblies with the built in pressure regulators leak in to the manifold .... common failure , hard to prove without test equipment

can you get misfire counters ?
both current and history , if yes , display them at hot idle - i bet they will flag 1 or more cylinders

hi HC is always misfire or cat converter or both
hi nox , restricted EGR or some cylinders can be lean because the 02 sensor corrects for total fuel trim , if you are subtracting 8% , the system is correcting for 1 or 2 rich or misfiring cylinders and the rest of the cylinders are getting the same correction
so they are lean

bad cat also is suspect for hi nox but you need to resolve the subtracting fuel at idle thing first

what software are you using ?

[Burned]

When I had a friend check with his Snap on tool it had a random misfire. So there is defiantly a problem there.
I have replaced the injection spider with the newer MFI system last year when I thought I had a stuck poppet and leaky regulator.
Yes these motors have a electronic MAF sensor in the snorkel.

I was scanning with a ELMSCAN 5 USB with Scanmaster software.
I will not be able to check for misfires on this tool.
Maybe those Mode 6 failures can tell me something if I can decipher them.

I am going crazy here because of the amount of things I have replaced.
The cap, rotor, wires and plugs are fairly new. They are also my second set after a shop replaced them again on me. I pulled the distributor on the weekend to look for a worn gear or shaft. Timing chain has some wear. I am thinking the camshaft retard may be off. These motors have a fixed distributor, so i would have to ovalize the hold down bolts to be able to adjust it.

Replaced so far in the last year and half
Plugs, wires, cap, rotor
Intake manifold gasket 5 years ago
Coolant temp sensor
Air filter
Fuel Injection spider
All 4 Oxygen sensors
Catalytic converter (old one was broken up inside)

[Burned]

The three Mode 6 tests I failed and what they are

TID 04 CID 20 - Steady State catalyst test bank 1
TID 07 CID 0C - No EGR off-idle test MAF Out of range high/low
TID 07 CID 0D - EGR decel test

[some_other_dave]

The numbers 32767 and 32768 showing up are a major red flag to any computer geek. Those are "magic numbers"; 32767 is the largest signed integer that can be represented (by one's complement) in a 16-bit word. That tells me that something is funky with the software, even if it is just trying to print a number it doesn't understand correctly.

Misfires need to be corrected. Fuel-smelling oil needs to be changed. (Period. It is no longer as thick as it should be, so it is not protecting your engine parts correctly, and it also contributes to tailpipe emissions.)

Oil that smells like fuel is either due to a very very rich mixture, or possibly from a misfire. So finding and fixing the misfire might solve the problem of fuel getting into your oil.

Once you have the misfire corrected and the oil changed, try another test. You might be able to squeak by.

-soD

[Burned]

Originally Posted by some_other_dave

The numbers 32767 and 32768 showing up are a major red flag to any computer geek. Those are "magic numbers"; 32767 is the largest signed integer that can be represented (by one's complement) in a 16-bit word. That tells me that something is funky with the software, even if it is just trying to print a number it doesn't understand correctly.

Misfires need to be corrected. Fuel-smelling oil needs to be changed. (Period. It is no longer as thick as it should be, so it is not protecting your engine parts correctly, and it also contributes to tailpipe emissions.)

Oil that smells like fuel is either due to a very very rich mixture, or possibly from a misfire. So finding and fixing the misfire might solve the problem of fuel getting into your oil.

Once you have the misfire corrected and the oil changed, try another test. You might be able to squeak by.

-soD

Thing is, I cant figure out why its misfiring. I have changed plugs, wires, cap rotor, even pulled the distributor and looked for wear. The injection system is a year old.
Maybe the EGR is constantly dumping exhaust gases into the intake?
A few more things to try then its time to take it into a shop.

[mwebb]

Originally Posted by Burned

The three Mode 6 tests I failed and what they are

TID 04 CID 20 - Steady State catalyst test bank 1
TID 07 CID 0C - No EGR off-idle test MAF Out of range high/low
TID 07 CID 0D - EGR decel test

there it is again , i flagged it above
MAF sensor is out of range , may not be a bad MAF sensor .

a vacuum leak or clogged or restricted exhaust could flag MAF values as incorrect for conditions

EGR can not run if MAP is out of range as MAP is used for the EGR test
vacuum leak can affect MAP and MAF values .

what is intake vacuum at hot idle ?
should be 20 to 21" at seal level and more important needle must be steady smooth with zero flutter

your system may be in open loop as
Long Term Fuel trim can never be zero , LTFT should adjust total trim to keep STFT bouncing on zero , equal amounts above and below
your LTFT = 0 can not be in closed loop

did those MODE 6 tests fail ? or just not run ?
the ECM will never run a CAT test with a p0300

[Burned]

I guess the mode 6 isn't that important for emissions. My friends Blazer failed the same tests as mine. Yet his passed emissions testing with flying colors.

His MAP read 35kPa, mine read 32kPa.
The only difference I see in the reading of the 2 vehicles is my LTFT, and the fact that his passed all the "non-Continuous Monitoring tests" on the scantool.
Our MAF readings were the same at around 5g/s

The vacuum reading was 20 at idle and it held steady (no flutter)

I am going to pull the EGR and clean it, high carbon in these engines.
I will also take a look at the CAT, I hope its good, its only a year old!
Maybe run some propane around the intakes looking for leaks.

[Burned]

Swapping this out made a big difference!



Time to log more data.