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2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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hisdudeness47
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May 5, 2016, 4:13 PM
Post #1 of 22
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2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Hey guys, I've been having trouble diagnosing a hesitation at light throttle, but it doesn't happen immediately. The car drives fine for the first 15 or 20 minutes, but soon I experience a hesitation while lightly on the gas pedal as if I have taken my foot off the gas. It feels normal for two seconds, then no throttle for two seconds, then normal again, and it repeats like this at light pedal pressure. If I floor it, there is no hesitation. This problem makes it impossible to drive until I pull over and unplug my TPS and then I can drive around just fine in manual mode, shifting myself. Then after the car sits I can plug my TPS back in, drive around fine again for 15-20 minutes before the hesitation happens again and then I have to again unplug the TPS and drive in manual mode. I keep the TPS connected around town because idle is very high when the TPS is unplugged and I'm often driving no more than 10 minutes. It doesn't make sense to me why it takes a bit for this hesitation to begin and why unplugging the TPS and driving in manual mode seems to fix the problem. I've recently replaced my crankshaft position sensor, idle air control valve, purge control valve solenoid and the TPS. When I recently replaced the TPS, another problem I've been having recently, a high idle in park, was fixed, so there certainly was something wrong with the last one. I thought the hesitation was fixed also, but it popped up again when I went for an extended drive. I'm kind of at a loss for what would cause this. I just went on a 100 mile camping trip in manual mode no problem, but I can't be driving around forever with no TPS. I idle at 3000 with no TPS. Any help diagnosing this or ideas on what tests to run would be a great help. Thanks!
(This post was edited by hisdudeness47 on May 7, 2016, 8:18 AM)
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kev2
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May 5, 2016, 4:22 PM
Post #2 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Why not get the system scanned for codes? its FREE easy?
yes scan even if light is off.
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hisdudeness47
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May 5, 2016, 4:23 PM
Post #3 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Ah, I should have said, there's no codes besides the one that's thrown when I unplug the TPS.
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Discretesignals
Ultimate Carjunky
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May 5, 2016, 4:24 PM
Post #4 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Kinda of hard to say what is going on because there is no scan data available for us to see. I suspect maybe a MAF sensor issue, but you would have to test with a lab scope to verify.
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 May 5, 2016, 4:32 PM)
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hisdudeness47
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May 5, 2016, 4:35 PM
Post #5 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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So I cleaned my MAF sensor a few weeks ago, but that doesn't mean it isn't defective. Is a MAF sensor's operation something I could check with a multimeter?
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hisdudeness47
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May 5, 2016, 4:38 PM
Post #6 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Also, I just purchased an ODB II bluetooth scan tool and Torque Pro, but I'm really sure what to look for with a problem like this. Is there any data from that I could provide you that could assist a diagnosis?
(This post was edited by hisdudeness47 on May 5, 2016, 4:39 PM)
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Discretesignals
Ultimate Carjunky
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May 5, 2016, 4:40 PM
Post #7 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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You can check it with a volt meter, but the problem is that you need to be able to graph the voltage signal over time to see any signal drop outs or other glitches. The sample rate has to be fairly high and most volt meters don't have a high sample rate, so they average the voltage and hide signal glitches. The only thing you could do is to swap it with a known good one or find someone that has the equipment. It is just a guess on my part based off your symptoms. Drive-ability problems are extremely difficult to solve without actually being there with the right equipment.
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 May 5, 2016, 4:41 PM)
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hisdudeness47
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May 5, 2016, 4:50 PM
Post #8 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Guess it wouldn't hurt to buy a new MAF from Autozone, try it, and return it if it doesn't help. Thanks for your help. That's more help in 10 minutes than I got in days from the Hyundai forums. Anyone else have any ideas?
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Discretesignals
Ultimate Carjunky
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May 5, 2016, 4:50 PM
Post #9 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Trying to catch a glitching MAF sensor with a scan tool can be difficult also. Main things you should look at are engine coolant temperature and MAF grams/sec or lbs/min. Right down the reading of the MAF values when it is running good and compare them to when it acts up. Compare the ECT and the IAT when the engine is cold and make sure they match. You can also watch your O2 sensor voltages and do a wide open throttle test while driving in a safe area to be sure their voltages go high. This would tell you if the engine is getting enough fuel under extreme load. Some of the software in the vehicles can compare MAF information to the TPS information and perform a rationality test that could set some sort of MAF performance code, but that is a big ?? Like I stated the MAF being the culprit is just a big guess. The sensor reacts to the volume of air flowing through it, so make sure all your ducting and vent hoses are in good shape, not ripped or torn.
Here is a TSB for a hesitation. It doesn't go indepth as to when the hesitation occurs, but it is a possibility. Obviously it is software bug that requires a reflash at the dealer or shop with the capability.
Number: 04-36-017
Date: SEPTEMBER, 2004
Model: SANTA FE(SM)
Subject
2003-2004 SANTA FE(SM) 2.7L ECM REPROGRAMMING FOR INTERMITTENT HESITATION
DESCRIPTION:
Some 2003-2004 SANTA FE(SM) 2.7L vehicles may experience intermittent hesitation while driving.
This bulletin provides a procedure for updating the ECM (Engine Control Module) software with new logic to improve the above condition by using the Hi-Scan Pro.
VEHICLES AFFECTED:
^ Model : 2003-2004 SANTA FE (SM) 2.7L vehicles
^ Affected vehicle production date range
^ Produced through August 13, 2004
^ Affected VIN range:
^ Produced through KM85C73D15U855406
^ Area : North America
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 May 5, 2016, 4:58 PM)
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hisdudeness47
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May 5, 2016, 5:03 PM
Post #10 of 22
(4213 views)
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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In the Torque Pro app, I can add sensors for O2 Sensor1 wide-range voltage, O2Sensor2 wide-range voltage, etc, but I can also add sensors for O2 Volts Bank1 sensor 1, O2 Volts Bank 1 sensor 2, etc.... I'm not sure what the difference is and which ones I should be looking at for what you are explaining.
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Discretesignals
Ultimate Carjunky
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May 5, 2016, 5:12 PM
Post #11 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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That is totally different subject that would turn this thread into a classroom. You may need to do some research, if your interested, in oxygen sensor operation and how the computer reacts and displays information.
I can tell you that your vehicle doesn't use wide band O2 sensors, so those PIDs are not valid. You want to monitor Bank 1 sensor 1 and Bank 2 sensor 1 voltages. They will fluctuate between 0 and 1 volts.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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hisdudeness47
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May 6, 2016, 4:50 PM
Post #12 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Hey, so I monitored all 4 of my O2 sensors after a proper warmup, and I think we might be on to something! My bank 1 sensor 2 and bank 2 sensor 2 both seem to be bad, while bank 1 sensor 1 and bank 2 sensor 1 seem to be alright. Check out these graphs and see if you agree. Would this be a likely cause of my issues? I also didn't mention that I'm getting poor MPG....
Bank 1 Sensor 1: 
Bank 1 Sensor 2: 
Bank 2 Sensor 1: 
Bank 2 Sensor 2: 
(This post was edited by hisdudeness47 on May 6, 2016, 4:52 PM)
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Discretesignals
Ultimate Carjunky
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May 7, 2016, 8:52 AM
Post #13 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Was this recorded during the hesitation event?
Why do you think they are bad? The switching frequency looks good and they are crossing the 0.5 volt line. The rears are not going to be as active as the front because they are behind the catalyst which is using the oxygen in the exhaust to convert gasses. What are your long and short term fuel trims? What was the engine rpm while you were recording? During the hesitation how do your front sensors react? Also understand that the engine controller is monitoring the performance of those sensors and you don't have any O2 codes.
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 May 7, 2016, 8:59 AM)
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hisdudeness47
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May 8, 2016, 1:02 AM
Post #14 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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I did this test at idle with a warmed up engine. I thought all the sensors were supposed to fluctuate regularly between .1 and .9 volts. The upstream sensors seem good to me, but it seems to me like the downstream sensors are not giving any kind of steady reading. I'm new to this, forgive me! I drove around and tested the long term fuel trims and they were both around +4.
(This post was edited by hisdudeness47 on May 8, 2016, 9:49 AM)
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Discretesignals
Ultimate Carjunky
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May 8, 2016, 10:47 AM
Post #15 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Those types of sensors will fluctuate between those voltages due how the engine controller is controlling the fuel trim based off the sensors' voltages. The front sensors are mainly used to trim or correct the fuel to air mixture, so that the catalysts are in an environment that makes them the most efficient. The rear sensors are used to monitor the performance of the catalysts, so if they become inefficient at converting harmful gasses to less harmful gasses the computer can flag codes to report a converter performance issue. Sometimes the rear sensors can be used for fine fuel trimming or to check the bias of the front sensors to be sure they haven't shifted.
The powertrain control system is a complex system of different components and systems that work together. You are just seeing one part of that system. You need to understand the entire powertrain control system fully to be able to troubleshoot it and its system. As you can see the scan tool you have doesn't tell you what is wrong or what needs to be replaced. It is a tool that is used to give you information about various parts of the system, so you can draw a picture of what is actually going on. That picture guides you or gives you direction on what kind of problems could be causing those symptoms and what tests you should use to validate your suspected culprits.
Like I mentioned, once the catalysts are warmed up and operational the rear sensors are not going to be mimicking the front sensors' voltages because the catalysts are using the oxygen in the exhaust for the conversion process. The signals from the rear sensors are going to be more flat and have way less cross counts unless the catalyst are faulty or not at operational temperatures.
The hesitation issue may or may not show up in the oxygen sensor wave forms. Even if it does, more than likely the response from the sensors will be just a response to the hesitation problem and not caused by the sensors themselves. Hesitation is caused from lack of fuel or misfiring on engine speed acceleration. Misfiring could be caused by ignition, mechanical, or fueling issues. The hesitation may not be engine related, so keep that in mind.
Since there is a software bug fix out there for that, you should probably focus on that first. The TSB may or may not apply to your vehicle, but you should find out. You could spend days troubleshooting and swapping parts, but all that is fruitless if it is a software bug at the top of the ladder causing your issue.
To really see what could be going on you need diagnostic software that can record multiple data parameter identifiers and plot them on a graph over a long period of time. You also have to be recording when the fault is present. Then you can sit down or even share the recording to see if anything in the data gives clues as to what is happening and where to look.
Below is recording from a high end scan tool that you can actually use cursors to move through the graphs to see the values of the PIDs at certain points in the recording. You can see multiple frames of information and get a better understanding how the entire system is operating than viewing just one or a few pieces of static information at a certain time frame. You can also see how different PIDs interact with each other.
For example, you notice that as the engine rpm rises you see an increase in ignition advance, load and injector pulse width. The increased pulse width or on time of the injectors allow more fuel to enter the cylinders as the throttle is opened. This causes an increase in engine speed. Since the engine is speeding up, the ignition timing needs to be advanced, so spark occurs earlier to allow complete burn of the fuel/air charge in the cylinders. The load is a calculation made by the engine controller based on various sensor inputs. The load is equivalent to the torque output of the engine. The computer may use that information for traction control or to protect the transmission. You could also graph the TPS, MAP, and MAF parameters and see how they relate. If you understand the systems and components of the power train control system, you can sit there with this recording and figure out how the engine was running and what all the inputs and controls were doing when a fault occurred. These are the kind of tools most drive-ability techs use. We can share these data files and review them just as you can on your scan tool at home.
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 May 8, 2016, 11:45 AM)
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hisdudeness47
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May 8, 2016, 1:24 PM
Post #16 of 22
(4100 views)
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Thanks for the response. It just seems to me like my downstream B1S2 is not flat at all. It's all over the place. Also, my downstream B2S2 is extremely low around .1. From what I'm reading the downstream sensors should be relatively flat between .35 and .65. My downstream sensors are anything but that. I realize the downstream sensors may not affect my hesitation problem at all, but I do want them to be behaving like they should.
(This post was edited by hisdudeness47 on May 8, 2016, 1:25 PM)
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hisdudeness47
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May 12, 2016, 6:31 PM
Post #17 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Update: the dealer diagnosed that my throttle cable and cruise control cable were both too tight. Loosened those up and fixed! No more hesitation. However, I still get poor MPG and my car just threw a P0420 code, low catalyst efficiency Bank 1. The graphs I showed earlier certainly seem to show that the Bank 1 cat isn't operating correctly or something else is up. Any ideas?
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Discretesignals
Ultimate Carjunky
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May 12, 2016, 6:47 PM
Post #18 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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That is interesting. You would think with a too tight cable that was holding the throttle open, the engine would idle higher than what the PCM was desiring. Do you remember what the throttle position sensor voltage at idle was before they readjusted the cables compared to now? Did they clean the throttle bore and plate also? Hesitation is possible with the dirty throttle body.
B1S2 is showing a similar pattern to B1S1 which usually means a failed cat. To be sure hold the rpm at 2500 with the engine warmed up and then see if the voltage patterns are looking the same. Be sure your graphs are not auto ranging. If the PCM flagged a P0420 for an efficiency issue, 90% of the time it is a cat. Just make sure you don't have any exhaust leaks or misfires. Ignition or mechanical related misfires will cook a cat or degrade it. Thanks for the update. 
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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hisdudeness47
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May 12, 2016, 6:58 PM
Post #19 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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I seem to remember it being at 12.4 before the adjustment. I'll check it now. The guy at Hyundai also pulled the cruise control cable out of its guide saying that the guide actually causes problems and should not be fed through it. Maladjusted tension was all it was, I suppose. I'll go for a drive and post new Bank 1 sensor graphs shortly.
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hisdudeness47
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May 12, 2016, 8:23 PM
Post #20 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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1. The throttle is at 9.0 now at idle. It was idling at 1000-1100 RPM in Park before the adjustment. The idle in Park is exactly the same as Drive at 700 RPM now. Much better idle.
2. I regraphed the Bank 1 sensors at 2500 RPM after a warmup. They are almost exact. Here they are....
B1S1: 
B2S2: 
So, I likely have a failed cat? You said that this is the case 90% of the time, but what is the other 10%? Also, I did a vacuum test and the exhaust didn't seem to be clogged. The vacuum gauge responded exactly as it should. If the cat is not clogged, but is just broken, would that still explain my poor MPG? Is a broken but unclogged cat going to affect my driveability and MPG or just my emissions?
(This post was edited by hisdudeness47 on May 12, 2016, 8:27 PM)
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Discretesignals
Ultimate Carjunky
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May 13, 2016, 4:26 AM
Post #21 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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That is good stuff that your posting because you have data to back up your suspicions. I'd definitely say the cat is bad from that waveform. The other 10% is exhaust leaks, software issues, O2 problems, other engine drive-ability problems that would make a cat not function properly. I really don't think you have 02 issues and software problems may not cause the cat to just flat out not work. There has to be a reason it failed. Maybe removing it and taking a gander at the substrate may give you an answer.
Many factors will influence poor fuel mileage. Inefficient cat probably isn't one of them and will only affect emissions.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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hisdudeness47
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May 13, 2016, 8:33 AM
Post #22 of 22
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Re: 2004 Hyundai Santa Fe 2.7L 4WD hesitation at light throttle after 15-20 minutes of driving
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Thanks so much for your help, man. You're killin' it. Now it's on to my next diagnosis, what caused my cat to fail? I'd wager that whatever caused my cat to fail is also what is causing my poor fuel efficiency, not the cat itself. Would you agree? What sort of things could have made my cat fail? What should be my next test/course of action? How can I test for exhaust leaks? I bought this vehicle about 1000 miles ago at 110K so I can't be 100% sure about everything that has been done, but I do have some records. Looking at previous records, it had its Hyundai 90K service about 14K miles ago with spark plugs, air filter, fuel filter, new battery, tranny flush and fluid, fuel injector service, and timing belt. Coolant temperature sensor was replaced about 10K ago. Oil and oil filter were done about 1000 miles ago. Thoughts about where to start looking? Getting 15 MPG hurts my soul and I need to figure out what fried the cat before I replace the cat! Thanks again.
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