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Discussion in 'The Garage' started by NJjeff, Feb 11, 2014.
Replace the fuel filter while you're at it...under the back seat.
I did monitor the both O2 sensors I believe the outputs are acceptable.
(snipped from post #14)
Within I'd say a few minutes the O2 sensor very quickly began to oscillate between .85 v and .03 v. Values were slightly changing but the high and low centered around those numbers. It switches quickly, I'd guess like 2 cycles per sec.
Rear O2 sensor switched slowly from .8 (something) to .03 (something). Frequency was several seconds before a change.
I've owned the car since 22K miles (now 104K) and I've never added anything but regular fuel to the tank.
I was tempted to replace both sensors but I hate throwing parts at something. From what I have read the O2 sensors output values are normal.
29 - 11 = 18 in of vacuum
I think you have it.
I did receive a reply (very quickly!) from the OBD software mfg. I snipped out most of the reply but below is the bulk of it.
MAP is manifold absolute pressure.
(Manifold Vacuum) = (Atmosphere) - (MAP)
I think I got it now.
So take a partly cloudy day, the barometric pressure is around 29". (not sure what it actually was yesterday)
Subtract it from the MAP sensors readings (in my case ~24 when hard on the throttle)
That = 5" of manifold vacuum at nearly WOT.
When going down hill closed throttle it was around 7, so 29 - 7 = 21" manifold vacuum.
It makes more sense now.
Understand all the numbers may be off a bit. I was driving to work with the laptop on the passenger seat. I thought I was recording data when in fact I forgot to click the button. So I glanced down at times to briefly watch the numbers. A few stuck in my head. like mid 20's with heavy throttle and single digits coasting.
None the less I now believe the MAP is providing correct numbers. But with a better understanding I will test it again.
Who makes the obd test system? Try to make sure the canister system does not allow fuel vapor in the intake and cause a rich condition. Also a digital volt meter on the o2 sensor can read voltage moe accurately than a scanner . Cause a artificial enrichment and watch voltage or introduce a vac leak and watch voltage and will see if o2 is working properly. Also o2heater can show high voltage causing a false rich code. Scanner not fast enough to read actual o2 voltage changes ideally need a lab scope .
OBD.com is the Mfg. of the software and cable.
Now there have been a few issues with the canister system. Early on the purge valve was replaced. Next the air pump that checks for (i guess gas cap and filler neck leaks) failed. Later one of the tubes in that system developed a leak from rust. Good thing the car had a long warranty.
Yes there appears to be a slight lag when reading sensors. Easy one to see is the throttle position.
As b1pig posted it may be best to replace them. I did further Googling on Oxygen sensors and it seems as + 100K miles is a bit too long of a service life for them.
I'm in agreement with Larryboy. You have a power loss. The rich condition is caused because one cylinder is not getting enough fuel and misfires, so the unburned gas gets dumped into the exhaust.
You haven't mentioned any black smoke, or poor mileage, or the crappy suffocated feeling the engine gets with a too rich system.
I am not a big fan of fuel injector cleaners since I feel they do not do as thorough a cleaning as should be required but the Seafoam brand especially does make a noticeable difference usually, I'd suggest putting a can of that in and replacing the fuel filter is a good idea too.
There are companies that clean fuel injectors off the car. They also put on new orings and filter screens. Cost is around 20 an injector. I have experience with an ASNU machine. It works very well.
Unburned fuel/air mixture (misfire) would not cause this code to set and STFT & LTFT to go negative. If he had misfires, he should also see P03XX codes.
P0172 means that the average LTFT on bank 1 is below a predetermined threshold for too long. The ECM is subtracting (negative ST & LT fuel trim) because something is causing a rich condition. Or at least the B1S1 O2s to report a rich condition.
Vacuum leak (intake), leaking injector(s), plugged air intake/filter, incorrect MAP readings (looks like that is ruled out,) fuel pressure high (regulator stuck,) restricted exhaust, fuel contaminated crankcase oil, evap purge problems or, quite possibly even a O2s reading incorrectly.
I would start with a fresh set of oxegen sensors . .yes,all of them. it's past due for new ones. Rest the fuel trims to default if you can or simply clear the memory by disconnecting the battery for a few min. Drive it & see what happens . . .
If the problem comes back. Test the injector spray patterns. maybe you have a leaky injector or two on that one bank.
These are the most likely things to cause a code for one bank running rich.
Timing Belt. Check for missing teeth. DAMHINT.
The stumble, bog, comes in only at low RPM when I roll into the throttle. Example, Slow down, make turn, and re accelerate. If I use very little throttle and allow the RPM to slowly build I can than apply ever increasing throttle w/o a hesitation.
No black smoke that I have noticed. Mileage is normal. It has the feeling of no fuel. Like running out of fuel. But it does it at any fuel level.
I cleared the codes afew days ago but the light is back on. After I type this I'll read the code(s) and post. I have to get off line and carry the laptop to the car.
Yes it's seems to keep subtracting at times. Because once it builds RPM it runs as normal as it always has.
To answer some of the areas to check.
Vacuum leak: Could be. My main concern is the evap. system. I think I listed in an earlier post this system has had a few problems. I was thinking of plugging up the vac. line off the intake that draws through the purge cont. valve to isolate that system.
Leaking injectors: I guess with a fuel pressure gauge I could check the leak down rate after the car is off. Also answers the fuel pressure reg. question. Looks like a bolted in test port is required. It fit's between the fuel rail and the fuel line flange adaptor.
Air Filter: Is not too old, but I can easily check if mice made a nest. I'll do that when I check and clear the codes.
Crank case oil is about due for a change but I just checked it and does not smell of gas or appear diluted.
I will try to take a screen shot or a picture of the O2 readings and post it.
Can you tell a vacuum leak from the MAP readings at idle?
I'm thinking of changing out the O2 sensors but I'm kinda not sure as the readings look normal.
Timing Belt. Check for missing teeth. DAMHINT.
I changed it at 80 K miles. It could be but it does idle and run on the highway normally.
What a vacuum leak would cause is for MAP or MAF readings to be off (thinking less air is originally entering the engine to begin with) and, the ECM would prematurely start to go negative fuel trim to compensate. This is going off of GM strategy. Hyundai may be different.
Throw an old school vacuum gauge on it and see what you actually have at idle. Standard is ~17-22 in hg. Will vary with altitude. You should be at the higher end in NJ near sea level. A couple easy ways to check for vacuum leaks are use carb clean to spray around the intake, fittings, injectors. See if RPM changes or, watch your scan tool B1S1/B2S1 02s readings change.
Another way is to use propane to check for leaks. Same thing, look for RPM/02s changes.
Or, smoke test the intake.
Looks like Hyundai is charging $ to access service info. ($20 ain't bad) Take a swing by the local library and see if they have AllData Pro. It is usually a reprint of original service info. See what the code set criteria is, conditions for running diagnostics and, testing for this code. This is going to give you more information on what to watch for on your scan tool readings.
+1 on the library, also check online. Our regional library has a LOT of info online, you just need a library card number to access it for free.
Maybe this will help?
I see it as an injector dribbling when it should be closed, common rail and the injector is a shutoff valve. It's a perceived lean bog, but the data says it's a rich bog. I don't use snake oils, waste of my time. Downstream codes are an upstream problem 98% of the time, bad O2 sensor is extremely rare, but shops talk people into them all the time.
Weather has been very crummy lately. It's hard to tell much when driving in snow and I didn't want the distraction of a cable by my left foot and hardware on the passenger seat.
But weather is improving so I hope to re-run the laptop during my commute tomorrow.
larryboy, your post is interesting.
Thinking out loud here for a test:
So when throttle is closed at say highway speed injectors are shut off. The forward O2 sensor should remain near .1 volts (lots of oxygen, very lean) and stay there until some throttle is reapplied and injectors begin cycling.
If above is correct than a dribbling injector would keep the forward O2 sensor at a higher (richer) value.
Do I understand this correctly?
If that is the case how does a mechanic determine which injector is leaking? Also can you tell an injector is dribbling by a fuel pressure decay test (engine off)? The manual speaks more of regulator leakdown during a decay test.