- This topic has 6 replies, 4 voices, and was last updated 9 years, 9 months ago by
.
-
Topic
-
Has a known failed purge valve solenoid (throws code P0496 occasionally, hard start after refueling…) but has recently started to idle rough and is throwing code P0171. Not sure if it is related to the bad purge valve solenoid or not, but I was able to pull freeze frame data if anyone can help me analyze it and determine if there is another issue. I will hopefully be checking fuel pressure tomorrow.
P0171 SYSTEM TOO LEAN (BANK 1)
FREEZE FRAME DATA:
FUEL SYS 1 CL
FUEL SYS 2 NA
CALC LOAD(%) 21.2
ECT(*F) 190.4
STFT B1(%) 29.7
LTFT B1(%) 26.6
ENG RPM 1588
VEH SPEED(MPH) 32
SPARK ADV(*) 39.0
IAT(*F) 48.2
MAF(lb/min) 0.8
TPS(%) 14.5
O2SLoc B1S12_____
B2S_______
RUN TIME(sec) 635
COMMAND EVAP(%)0.0
FUEL LEVEL(%) 51.8
BARO(InHg) 29.8
ECU VOLTS(V) 14.070
LOAD VALUE(%) 21.2
EQ RATIO 1.000
REL TPS(%) 4.3
AMBIENT(*F) 37.4
TPS B(%) 14.9
ACC PEDAL D(%) 25.9
ACC PEDAL E(%) 25.9
COMMAND TAC(%) 0.8
-
Replies
-
Looking at fuel trims being positive the computer is adding fuel usually from a vacuum
leak. This link should help further.http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Here’s where I’m at now. Tested fuel pressure 52 PSI, drops about 10 PSI after 30 minutes with engine off.
I’v been doing a lot of research on fuel trims are reading O2 Sensor voltages. After the car warms up, the fuel trim pegs lean, and the primary O2 sensor reads between .015 .025 volts, barely any fluctuation mostly flat lines. The downstream sensor reads normal, then slowly matches sensor 1. So I have the fuel trim maxing out lean, and both O2 sensors reading lean. When I pop the throttle, the O2 sensors come back on line and the fuel trim normalizes. While driving everything seems normal but maintaining a steady speed the O2 sensors both read low.
I cannot find any vacuum leaks. Tried water, brake cleaner, and even blew smoke through the vacuum lines. I also cannot hear anything. It’s definitely running lean, what would be a good next step?
I had actually cleaned the MAF as well. Fuel pressure was 52 PSI.
Is there a specific way to test the MAF, or a specific operating range I can watch while the vehicle is running?
The best way to check all of these sensors, including O2, is to use a scan tool that can display the live data stream. The sensor operations are quite simple to learn and interpret, as long as you can access the data. If you will be doing a lot of DIY on your vehicle(s), you should invest in a scan tool.
If you have a scan tool, to check the MAF, watch its pid and snap the throttle. You should a sharp rise then a curve back downward. Edit: You could also do this with a voltmeter and backprobing the pins, but that is more difficult than watching the scan tool. On the voltmeter, the wide open throttle should hit between 4 and 5 volts (if it is a 5v sensor, most are) and then drop back down to between 0-1 volt on closed throttle. To find the correct pins to backprobe, with the key on and engine off, you would find a +12v and ground for the heater, a wire that reads 0v, this is the voltage reference and is 0 when the engine is off, and the other should read 0.1-0.5 volts. That is the one you want to probe and read volts from here to ground. There may be other wires in there too, such as an IAT connection or additional grounds, but you are only interested in the one reading millivolts. Start the engine, set up your voltmeter and probes, and while watching the meter, snap the throttle. You should observe the voltage spike and then fall back down as described above.
- You must be logged in to reply to this topic.