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2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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puke
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Jan 23, 2016, 4:05 PM
Post #1 of 9
(1286 views)
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2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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This xl7 had intermittently started to stall when braking and coming to a stop. Then it got often enough that I thought a shop could accurately diagnose it.
Took it to a reputable neighborhood shop (over 50 years in business)
They said the throttle body had a massive air leak and needed to be repaired before they could move on with it. I got a second hand throttle body, while informing them I thought the leak had NOTHING at all to do with my symptoms.
Replacement did not change symptoms at all.
Then they said it needed a new MAF, I explained I had just put one in 2 weeks before,..but they insisted. So I went and got a new one on warranty. Replacement did not change the symptoms.
Then they said the same thing again, so I got another new one on warranty. After the 3rd one, they blamed it on not being able to source an oem one. So I went to a wrecking yard and bought one from a wreck. Did not fix it.
I thought MAYBE if I kept at it, they would be emabarrassed enough at being wrong,..that they may actually put a smart guy on it. But after the last MAF, I went and got it and determined I'll have to deal with this myself.
so.,,I put my bluetooth scanner in and watched it on my torgue app. Went through all the stuff I could go through. And...finally found, that the upstream O2 sensors would start to go weird at the same time it would start stalling (would take ten or twenty minutes of driving to get it warm enough to do this).
Am I correct in assuming that if the upstream o2s get weird and no longer oscillate properly..that this is the correct solution. And, I mean, once warm,..they could stay at .6 or .8 for 3 or more seconds. And, even though I'm new at the "graph" part of the newer apps for the obd2 ports.....I did see on a couple maf freeze frame faults (if I even know how to read them correctly),..that the short term fuel trims were way negative 10 or 15 percent. So I think it was trying to compensate for the o2 sensors staying in the top half of the range too long.
Ok,
if you have any idea, please let me know. I no longer think that money is well spent with a professional mechanic.
For the record. when it was acting up...if I could drive it around a keep braking at every corner trying to make it stall. It would through a MAF code. But when I test the MAF,..it doesn't seem that weirdish...as far as voltage at the signal wire (it's been quite a few weeks).
Suzuki is out of business, so I've gotten parts at autozone or a wrecking yard.
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Discretesignals
Ultimate Carjunky
/ Moderator
Jan 23, 2016, 5:21 PM
Post #2 of 9
(1277 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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I would find it unusual that both O2 sensors are the culprit because they are acting the same during your problem. You are probably just seeing them responding to some other issue.
Is this storing any trouble codes?
Diagnosing drive ability problems and interpreting scan tool data correctly takes lots of hours of training and experience. You have to also consider the equipment you are using. That data your receiving is not real time data. I wouldn't solely rely on a graphed scan tool O2 sensor voltages. Not unusual to see short term fuel trims do that either.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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kev2
Veteran
Jan 24, 2016, 7:09 AM
Post #3 of 9
(1259 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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post all codes-
while doing that - this is an automatic? the 'stall'* happens when braking SO try shifting to N see if things smooth's out.
The vehicle is STOCK - no BS aftermarket that is so problematic. On that subject parts should come from Suzuki not junk yards or autozone...
What are the LTFT's and the STFT's -you said 10% but did not say LT or ST,
*I am reading this as all is ok UNTIL braking, starts the chain of stall events. Am I correct?
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puke
User
Jan 24, 2016, 9:32 AM
Post #4 of 9
(1249 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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In answer to your questions.
It is an automatic 4x4 totally stock. (suzuki is out of business here)
Shifting into Neutral does NOT change symptoms.
If I put it in REVERSE and heavily accelerate (once warmed up),..it will also cut out like it is trying to stall. This probably eliminates brakes as a factor, I believe. I was thinking it was an intermittent elec. connector affected by the force of heavy braking or accelerating in reverse. But now not so sure. Also, if I am idling, it will quit every once in a while. Starts right back up,..but it will die right out of the blue like someone just shut it off.
The long terms and short terms float very close to zero (especially the long terms)....except the few freeze frames I've gathered where the short terms were both identicle and between ten and fifteen percent. I gathered these freeze frames when I was driving around doing heavy braking over and over, making it stall....and it would finally throw an MAF circuit low inp. code. Has also thrown a couple MAF circuit input HIGH codes at the same time.,
The real time data confirms that when the car gets warmed up enough to misbehave...the upstream o2 sensors both get weird.. THey switch between low and high quite nicely until it has been running for about 15 or 20 minutes...then they get very slow and erratic....and tend to stay on the high side.
I had thought there was a TINY chance that the fuel pump's windings were going open intermittently (due to the problem happening during inertia....sometimes elec. motors act that way when they are failing)...So I installed a new bosch fuel pump assy. 3 weeks ago to make sure that was not the problem.
Yes, it is "braking" that will start the stall. Once it is very good and warm. Heavy braking will stall it on every stop...and sometimes light braking will also. Other than that,.. it has jerked a couple times at a low speed (like 10 or 15 mph) but the jerking doesn't show up much. The jerking "is" reminiscent of a faulty MAF. 5 MAF's in a month, 2 of them being factory,.. I am thinking not MAF. TPS is factory, I pulled the EGR and it was very clean,..I cleaned it anyway and put it back. A smoke test was done by the shop that did not ever find the problem.
One more thing I forgot,..I did unplug the MAF and ran it that way for a few days,.. It did behave better with the MAF unplugged....the stalling when braking problem would go go away (but it would idle too high...like 1200 or so rpms). But it would still jerk every now and then at low speeds... and would stall while idling now and then. I certainly can't run it that way due to smog checks.
I do appreciate your input,
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 24, 2016, 9:54 AM
Post #5 of 9
(1247 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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All this about braking directly related to stalling check for hose leaking, check valve and booster leaks.
When you remove the check valve from booster (try not to break it) it should go 'whoooosh' sucking in air showing it holds vacuum with engine off as it should. In fact if you don't feel power assist once or twice with engine off that would be high on the list of reasons,
T
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kev2
Veteran
Jan 24, 2016, 9:55 AM
Post #6 of 9
(1245 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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Is the CEL ON AND are there any codes? or did I miss them?
I was thinking a trans issue, but you say N does not change the stumbling....ie a TCC solenoid issue.
do you see any change in map when applying brakes? looking any direction to help check out this issue.
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Discretesignals
Ultimate Carjunky
/ Moderator
Jan 24, 2016, 11:09 AM
Post #7 of 9
(1240 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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.and it would finally throw an MAF circuit low inp. code. Has also thrown a couple MAF circuit input HIGH codes at the same time.
Have you tried wiggling harnesses under the hood to see if you can induce the problem while the engine was idling?
P0102 is low MAF input and P0103 is high MAF input. Both of those codes are circuit codes which means it is either a wiring, connector, MAF, or PCM issue causing that. The MAF is also powered by the main relay, so if for some reason it looses power or its ground that code can set. A MAF input circuit glitching can cause a stall.
The MAF sensor outputs between 0.6-4.90 volts depending on the amount of air flowing through it. If the voltage range gets below 0.6v or higher than 4.90 volts, the PCM is going to think there is a problem with the circuit. That might be why your mechanic was focusing on the MAF because they saw an issue with it, but didn't really try to figure out exactly why it was happening. Sometimes it takes lots of detective work and some fancy equipment to isolate the issue. I will admit that some mechanics don't have the knowledge of troubleshooting computer circuits efficiently and resort to replacing things to see if it fixes the issue.
If you have a digital storage labscope, you can tap into the MAF input signal at the PCM and monitor it while your driving to see if you have a glitch as the problem occurs. That will definitely let you know to focus on the MAF circuits.
Seeing how this stall is induced only when braking, you really should focus on wiring harnesses and connection problems. A harness could be shifting around and contacting something or a bad connection moves the right way and causes a circuit issue. Spend some time and do a really good visual inspection of the wiring under the hood. Also try the wiggle test and see what happens. Wiggle the harness and wiring the way you would think it would move as when the vehicle is braking.
This is an example of an analog MAF's voltage output waveform during a throttle snap. Notice the voltage is linear just as you would see from a throttle position sensor. The voltage is directly proportional to the amount of air flowing through the sensor. You would not want to see the voltage below or above the .6-4.9 volt threshold at anytime with the engine running. If there is a glitch, you will be able to see it with a lab scope because the lab scope does not average the voltage measurement due to its high sample rate and its ability to draw a graphical representation of the voltage input much much faster than any scan tool's graphical representation.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 24, 2016, 11:50 AM)
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puke
User
Jan 24, 2016, 10:26 PM
Post #8 of 9
(1207 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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Unfortunately, I do not have a scope of that caliber. I had a tektronics o-scope and gave it to my nephew 2 yrs. ago. Not sure I would even remember how to use it if I asked him to borrow it. It has been over 20 years since I've used it. Maybe 25. It may not even work for what we need to see.
Could there be another reason that the o2's sensors get weird after a few minutes of warming up?...I mean,..other than faulty o2s? I did read that when they fail, they usually fail on the high side,..rather than the low. ..And that's what mine are doing.
thank you so much
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kev2
Veteran
Jan 25, 2016, 7:26 AM
Post #9 of 9
(1184 views)
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Re: 2002 suzuki 2.7 xl7 4x4, upstream o2 misbehaving
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As there are NO CODE numbers to post, you are correct it is the o2 sensors.
The people at the parts stores are correct.
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