November 27, 2011 in 90 - 00 Lexus LS400, I am sharing my experience with this chronic problem of misfire at a certain speed when cruising that I see repeatedly in this forum, First I admit that this forum helped me a lot to find the cause of my problem but unfortunately after spending lot of money in changing many parts, First thing I want to say is that many issues can lead to the same symptoms of hesitation or misfire between 40 to 60 mph, Hesitation at this speed does not mean that the engine is only hesitating at this speed and THIS IS THE TRICK, The misfire is clearly felt at this speed because the torque converter clutch is engaged that means the engine and transmission are considered as 1 unit so any slight misfire in the engine will be felt in the transmission and this is happening only when cruising. Ever since they replaced the plugs everything works AMAZING and the car drives really smooth. Especially around 45mph. Either there will be too much air or fuel, or too little. I have a Denso 234-4167 Oxygen Sensor that I ending up not needing. I suspect you cleaned, as anyone would, the MAF/IAT sensors at the same time, more likely the actual "misfire" cause, as installing the O2 sensor. Fuel mileage is bad now as well. Vacuum leak will affect idle before anything else and certainly not at 40-45 mph and nowhere else. Replaced the rear differential's front mounting cushion to clear up the problem. If I should need to change out the metal fuel lines, does anyone know the correct size for rubber tubing to connect from the gas tank forward? But if this sensor is bad, then the wrong amount of fuel will get injected and cause engine hesitation. Thanks for the thoughts and suggestions. x2 on the fuel system. 1) Either transmission chooses wrong gears around 30-40 mph speed or something else, but car jerks sometimes significantly. Nothing else has been done since I've had it. Have a 1998 manual trans. When this happens, the traffic lights indicator works abnomally (blink faster). I'm having the same problem and being discussed in another thread. YourMechanic All rights reserved. Car has about 47K miles and has had all maintenance performed. Im hoping not needing internal work .. wondering if oil on plugs could be cause faulty manual fuel pump 0 2 sensor ,dont hear any vacuum leaks.. just seeing if one those could be the problem before start tearing down to see if o ring or piston rings are causing oil to fouling my plugs .just with not smoking maybe just fuel problem not enough or coil not getting hot enough ? Wrench Set: http://amzn.to/2kmBaOU5. So now comes the task of draining and cleaning the gas tank. My 2001 Acura TL is starting to hesitate when accelerating, then starts slowing down. Copyright 2023 Leaf Group Ltd. / Leaf Group Media. This is what it means when the car engine hesitates. just had this problem with a 2002 saturn sl2 turns out it was a fuse under hood labeled TRS That rules out 2, 3, and 4 of your theory. The engine will continue to rev as the car tries to accelerate above that speed, but the car will not be able to shift into gear for further speed. Hesitation Problem with 2007 LE I4. That's also why a crack in the exhaust, even downstream of the O2 sensor element, will result in a CEL, oxygen can get to the sensor before it has time to cool. ;), Yes before changing the O2 sensor, The MAF/IAT sensors had been cleaned AND even changed without any improvement, One more thing I want to mention is that the O2 sensor was completely dead (no reading for any resistance), I knew that this sensor was faulty (I had a CEL) but I could not imagine that this is the reason of misfire, that's why I left it to be the last option. Only to find out that it was my EGR what things should i check first? Entrants are required to release YouTube from any and all liability related to this giveaway.17. Forgot to mention, older cars like yours and mine will often develop vacuum leaks within the intake system. Even if you purchased it online, you might be able to get a store credit at a local retailer like Autozone, Advance, Pep boys, O'Reilly's, etc. Then you will experience engine hesitation which is most noticeable at low RPM. Amirkade Tighten gas cap / seemed to go from constant to intermittent. Q: My car jerks slightly when I'm at a steady speed or trying to stay at a constant speed only around 40mph to 50 mph. Put the clear filter on and we are up and running past 40-45mph without the sputtering, hesitation and stalling. Saturn SL with 169450 miles.. about 50 miles ago she started stuttering from front to back while in 4th gear going about 35 mph also in 5th gear going 70mph. What can I do with my Toyota Corolla sports,Ive changed so many things like fuel pump, injector, spark plug,fuel filter yet it still hesitate..help the helpless. http://www.g6performance.com/forum/showthread.php?t=22038. Why would my 2004 Dodge ram 5.7 keep throwing a map sensor code and I changed out the senser and the computer and now that I have a new computer it hesitates on takeoff. This helps the engine control unit determine the right amount of fuel to inject into the chamber. Fuel filter. Fiberglass tub. Or show off your own car mod on Wednesdays. There are a range of reasons why your car is juddering when you accelerate. Usually due to rust clogging the fuel filter because the tank if full of rust particles trying to make their way into your carb to clog that. Checked it for codes? If you click them and The only way I know to test those is to heat the element in our oxygen rich atmosphere and test for the output voltage to be in the proper range. You will need to figure out the cause of this problem and get it fixed by an experienced mechanic. While driving the vehicle at constant speed (from 20-40 MPH) the vehicle begins to jerk upon acceleration. A forum community dedicated to Ford Focus owners and enthusiasts. Sign in or register to get started. Thumbnail software: http://amzn.to/2k7tz6CCheck out the tools I use and highly recommend https://goo.gl/rwYt2yScotty Shirts and Merch https://goo.gl/pTAecaSubscribe and hit the notification bell! I also smell a burning smell coming from under the hood when driving and I dont know if its oil or fuel etc. Problem is more noticeable on hills/slops. The mass airflow sensor, also known as the MAF sensor, is connected to the air cleaner. When I took ownership of it, I had the oil changed and it needed an new motor mount and front brakes to pass inspection. moving you to the technical section, should get more views there. The vehicle has a stumble like a misfire(I think anyways) when driving. help please! This did not fix the problem, just made it worse when driving. Car hesitating while driving. Hesitation. Once this started to happen I immediately turned around and went home. Never any sponsored content, just the truth about everything! The car seems to hesitate in 4th gear right around 43 mph. How to Fix Car Hesitation, DIY with Scotty Kilmer. Also, a loose motor mount, or rear diff'l mount, might result in a tugging feel due to the resulting "in and out" action of the lockup clutch, at those speeds. I purchased my Torrent October 2014 and it had approx. Could be a number of things. Sure hope not but seen it happen on other cars. Instead of going faster by stepping on the accelerator pedal, the speed will be reduced. Not sure whether the procedures are applicable across all 1st gen models, though. Clogged fuel filter. Could it be a thing like the TC engagement going wonky? The radiator fan operates on a fused circuit with high amperage relays to drive them. Hesitation and Stumbling when throttle is applied Ford F-150 2001 105693 miles Accelerator ECU Wiring Jerking/Hesitation Cannot get truck to accelerate smoothly. my jeep hesitates to accelerate and other times its running great.Took it to get diagnosed and they say nothings wrong. For a better experience, please enable JavaScript in your browser before proceeding. Are you asking if oil on plugs could cause a bad fuel pump? Changed Fuel filter. Once the exhaust is supplying HEAT the sensor will provide good outputs. ", Now I need help and I am not sure if I should start a new topic or not, This is related to error code 47 in traction control (When idle switch is ON, sub-throttle position sensor signal is 1.45V or higher), Any ideas if that means that I should replace the sensor or it can just be adjusted, Yes you are right but it seems that by chance the sensor itself was also out of order. Any ideas? Misfires can be related to wrong plugs being used. This could be accompanied by a hesitation in the motor when driving. Camry 5th and 6th Gen '02-'11, Solara '04-'08. Good work ehabmarco. describing the symptoms (which are extremely Started February 14, By I decreased my speed to around 40 mph and the sputtering stopped. 1. the S series doesn't have a MAF but a MAP If so, the answer is no. When this is not working properly, you may also notice a strong smell of fuel. owners, Over 25,000 topics, from beginner tips to technical You are using an out of date browser. Haliuna Tool giveaways every Monday to help you with your own car projects. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Hesitation on acceleration. You should clean your MAF sensor if you haven't lately. Upload or insert images from URL. Affiliate Disclosure: We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. Is there any downside to having two gas filters in a fuel system? Fuel System. Entrants that do not comply with YouTubes Community Guidelines will be disqualified: https://www.youtube.com/yt/about/policies/#community-guidelines16. point. Sometimes simply cleaning the MAF may do the trick, too. Same symptoms as you describe. I can barely discern a vibration in the vehicle, but if I have my foot just over the accelerator pedal, I can feel it vibrate in unison with the noise. A pop and hesitation is likely a backfire. The only issue was that the car would shudder pr even buck a bit ONLY at speeds around 40 MPH and ONLY when the accelerator was backed off of slightly and when an attempt was made to feather the pedal and maintain a steady speed. Battery draining and charging - 2007 Jaguar XK. I have a Denso 234-4167 Oxygen Sensor that I ending up not needing. https://goo.gl/CFismNScotty on Social:Facebook https://www.facebook.com/scottymechanic/Instagram https://www.instagram.com/scotty_the_mechanic/Twitter https://twitter.com/Scottymechanic?lang=enThis is the people's automotive channel! This along with using 87 octane or higher gas solved the issue entirely. No code. Not if its unfamiliar to the audience or needs to be disambiguated. And be aware that exposing a perfectly good, even brand new, O2 sensor to our oxygen rich atmosphere while the sensor element remains heated will/might "spoil" the sensor, cause a CEL, for the first 100-200 miles. If you give it WOT the stumble will not happen or if you do like a passing a car event, the problem . The winner will receive a reply to their originally posted comment in the video and will also be announced in a newly posted comment by Scotty around Sunday 9 am CST. Doesnt using an abbreviation only to then state what the abbreviation stands for really defeat the purpose of aforementioned abbreviation? Misfire is due to ignition, or lack thereof. Ive been lurking this forum for a while and tried to read every forum post related to this problem Im having. replace if needed . If press hard it downshift, revs high and pull but it is inacceptable driving style. Any thoughts? They are as follows: Bank 1 Sensor 1 - Driver's side (left front) on exhaust header. Do I need to get a specific tool, or take it somewhere to get tested? thats how I fixed mine! 2 people found this helpful. This requires closer diagnosis. There's a wealth of information to be found in what you get from it. Please refer to CarGurus Terms of Use. I have a 1996 Saturn SC2. It also makes noise when the cars sitting at a light or stop sign. You'll get info from other sensors, as well, like the MAP. The winner will be chosen at random.10. You might need to replace your MAF sensor which is your mass airflow sensor and definitely check your fuel rail and fuel injectors. What could be causing this? Had one of my U joints replaced. WHY DOES CAR HESITATE AROUND 40MPH AND STARTS TO JERK. Changed Fuel pump 3 times within 2 weeks 2. It is real worse on highway when cars get hot. If you purchased it locally and do not have the receipt, just take it back and they may have the sale on record. It ran When the engine reaches operating temperature both Hello, thanks for writing in. So new spark plugs, battery, oil changes etc. . Idles a little rough at times as well. My Toyota Corolla Sport 2003 model started hesitating while at speed, I consulted mechanic and they change fuel pump, filter MAF, check the throttle position sensor, its like its not working, I have to start twice unlike before.. what should I do? (Kirchoff's third law), Measuring is knowing.. but only if you know what you measure. fuel pump. a sticky valve . When does it happen? ehabmarco When the transmission shifts, engine noise usually will quiet down, and the RPMs will drop. 94,000. The jerking happened in my car also(G6 V6 GT). We'll see how that goes and move forward. It happened to her again yesterday. It's frustrating to say the least! Bill Gate's would stoop to driving an LS? It doesn't happen at lower speeds. 1D10CRACY 60.2K subscribers Subscribe 3.1K 583K views 5 years ago My 1999 Lincoln Town Car developed. If you are still having trouble, From what you've described, it sounds like you have a head gasket leaking into the engine cylinder and then out of the exhaust. Battery Pack Car Jump Starter: http://amzn.to/2nrc6qRAmazon Version of Fuel Pressure Tester: https://amzn.to/2pDXiDsMechanic Monday Official Rules:1. Aug 22, 2018. Steve. It is really noticable when pulling out and gradually working up to around 40MPH. If you have not cleaned your fuel injectors for a long time, then theyre probably corroded with carbon deposits or other debris. Based on this information, the engine control unit will know if there is too much or too little oxygen being ignited in the chamber. You must log in or register to reply here. I had my throttle body cleaned, spark plugs replaced, wires replaced, had my driveline completely checked because at first it felt like a vibration but it is different. Common issues include: Have you taken it to a local mechanic for an inspection? Jump to Latest Follow Follow I think Sounds like your car is entering limp home mode. would it benefit to replace the air induction system with an after market intake, or just go with a standard air filter replacement? Please see our. I had it flashing CEL for 10 seconds but it never stored a code (trust me, I have the stuff to find out). You might want to drain a little fuel into a glass jar while you're doing it "just for giggles". Getting frustrated with money spending on hesitation problem.. mechanic have change injectors, pump, new iridium spark plug, filter and MAF.. Car engine hesitation is a noticeable problem that can occur as youre driving. I put on a new fuel pump and still having the same problem. :banghead: kilroypr. Ignition, fuel system, vacuum, or torque converter issue would be my guess, but any of the above will set a code! I just recently purchased my 00 Focus SE with 96,xxx mi. Indeed, over time, vibrations, the pot fasteners on the automobile chassis can come off.The most common reason for your Mitsubishi Outlander to have a clunking noise/sound coming from under your car is worn brake pads. Actually you can probably get your purchase price back very easily w/o reselling. Scottys Top DIY Tools:1. Have a mechanic trained in vehicle electronics inspect the radiator fan (https://www.yourmechanic.com/services/cooling-radiator-fan-motor-replacement) for You have two starter relays. You could check basic things like spark plugs and wires, injector functionality, and engine air filter cleanliness. Hesitation/Stuttering While Driving Between 40-50 MPH vicjrblue Member Posts: 1 January 2016 edited January 2016 I purchased my Torrent October 2014 and it had approx. What could be the cause? Took the car to the dealer to have it . So Sunday we packed up and headed back home, and about 30 mins into the drive traveling about 45 mph the engine started sputtering. We may earn a small commission from affiliate links and paid advertisements. These are the f-body part #'s. About $65 for both solenoid and valve from Dal. My 2007 Ford Edge hesitates/ jumps at 60-70 mph. It's FREE! If i slowly and accelerate and do not push the pedal with force and try to keep the speed constant around 35 mph and then slowly accelerate from that speed it almost hesitates, feels extremely sluggish.. Saturn 4 door stick , 1.9 . Nissan sentra 2012 My car hesitate on red light. Also having this issue, wondering after doing everything except a map sensor could the generic TPS be a thing? No problems starting and traveling at slower speeds but once again 20 mins into the drive traveling between 40-45 mph the sputtering began. 1) Throttle body is more of a rough idle phenomenon, not very noticeable at higher speeds as the caked up residue is insignificant at wide open throttle positions. Posted by Anonymous on Mar 16, 2015 Answer Pierre Laplante Ford Master 2,061 Answers Posted on Mar 16, 2015 Open Questions: that I should have all the fluids flushed and replaced soon. Camera Microphone: https://amzn.to/2Evn1675. Cleaned that off and the problem went completely away. Made with in Silicon Valley. It does it most often when you are barely on the gas at 45 to 50 MPH and then you press the gas to accelerate. 2014 Ford Escape with 88k miles. Car hesitates when accelerating. Id take it back and have them double check their work. Camera Tripod: https://amzn.to/2Jwog8S6. Turns out the spark plugs and wires were just worn. Mechanics computer says one of my engine coils needed to change and so I changed all of them. The winners full name and address will only be used to mail the giveaway prize to the winner and nothing else. We took the car to the dealer where we purchased it and they were unable to find anything because there were no codes present. I find the best price for oxygen sensors, and quality, the densos on amazon are pretty much literally a perfect fit just like OEM. Oct 30, 2005 I have a 91 RT TT Stealth, about 48,000 miles. 1970 FJ40 Grey, 4 inch lift, Winch, Aussie rear, ARB front. andbeyond, Nov 16, 2017 #20. For me the magic speed was 45 to 50mph. Follow the red battery cable to the inner fender relay and this should be your problem. The car hesitate when i step on the gas. What could be the problem? Step 1 - Check the ignition coils and spark plugs. This helps sustain the proper air and fuel mixture while the vehicle is in use. For a better experience, please enable JavaScript in your browser before proceeding. If you're driving 40 miles per hour and think the transmission might be going bad, check for these several symptoms. So my rav just started this weird shaking/chattering at around 30-40 mph. Pasted as rich text. necessary and make sure pcv valve is good I have changed the spark plugs. Why your car may be jerking, bucking, hesitating, or shaking in town or at highway speeds! We took the car to the dealer where we purchased it and they were unable to find anything because there were no codes present. 11. If it's less than 2k rpm, then you have the old programming, and should get the upgrade flash to the transmission (by a different dealership if need be). The reason why car hesitates when accelerating uphill is simple! Asked by ESBJr Jan 05, 2016 at 01:21 PM about the 1996 Saturn S-Series 2 Dr SC2 Coupe. Started September 12, 2022, Lexus Owners Club of North America Michael Davidson started writing screenplays in 2003 and has had a screenplay professionally produced. It did great going down there and throughout the week that we stayed. Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. However, sometimes car jerks when accelerating is a common problem faced by several car owners. Any misfire codes? If yes, what happens at 40 to 45 mph ( with light throttle) is your car is going into 4th gear. The '90 and one of the '92's are now off the list. It comes on as I get below 40. $29.93. around 40 mph. or Mass Air Flow sensor. If that doesnt do the trick, you may need to have them professionally cleaned or simply replaced with new fuel injectors. How to stop car hesitation. to Amazon, eBay and other sites may include affiliate code. Once Im going faster or slower it stops. Can you narrow down when it hesitates? It doesn't happen consistently. Can you help diagnose? . I have a '96 saturn sl1. Sounds like it does not like the autozone tps sensor. The car likely would still run fine at lower speeds, but it should be taken to a mechanic immediately. The fan motor itself is also a possible and common failure point. Car is If after replacing them I still have issues, I'll post back here for more possible solutions. CLEARED CODES AND CAR DRIVES FINE. I am going they the same issue with my sons 99 How to fix car hesitation. It appears that if you had "read" the actual code it would indicated an open O2 sensor HEATER, not the sensor itsself. Come join the discussion on performance modifications, accessories, troubleshooting, maintenance and more! they were not sure how to fix it. Also carbureted It idles fine revs up fine takes off fine but when get it under load starts bucking and more gas you give the more it wants to die . There are several reasons you might be getting backfires and hesitation. Just for giggles try putting in a water-remover fuel additive to the gas tank and see if there is any difference. Its loke being in the Any suggestions? Check plugs / wires , it may have I took several days before reseting the CEL "took". year amongst other things. Misfiring might be occuring. Bella Online: What Does a Car Transmission Do? 4. Take off exhaust manifold and clean the I recently wrote an article on limp mode, which is due to be published soon. Still my is not starting smoothly. Now it is starting to stall when stopped. When I take the car out of gear there is no shutter. By If still having issue after that let me know. I unhooked the old filter and I could not believe the junk that came out of it. We have a 2008 G6 with a V6 engine. I have a 1978 FJ40 which I've owned since 2007. Amazon Version of Fuel Pressure Tester: https://amzn.to/2pDXiDs2. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register. this issue started when I had about 97000 miles and has gotten worse. for an ignition miss. You don't even mention coils which are a known weak link of these cars. Hesitation will be the beginning of your troubles so look at it as a warning sign if you notice your engine hesitate when you accelerate from a stop. When this is not working properly, you may also notice a strong smell of fuel. It doesn't happen every day but more days yes than no. I'll see how the car runs as the weather gets warmer here in Chicago. My front end shakes when I accelerate at low and high speeds 2003 Pontiac Grand Prixh, A Buyers Guide to the 2012 Mercedes-Benz ML350 BlueTec, A Buyers Guide to the 2011 Mercedes-Benz ML450 Hybrid, How to Replace a Car Battery Temperature Sensor. Weather seems to have an effect though. Mechanics have been little help to this As the car approaches 40 mph, the RPMs will increase in the engine. wish to see you more in the coming days. I put my fuel pump direct without a return pipe. I tend to agree. Join the Lexus Owners Club and be part of the Community. My 2017 Hyundai Elantra is hesitating shifting right. Only one comment per entrant is allowed and more than one comment will not increase your odds of winning.5. 45 mph it sputters I have changed the TPS, coil, coil igniter/module, plugs, cap, wires, rotor. When the air/fuel mixture in your engine is too rich, a blockage can develop in the catalytic converter over time which disrupts the airflow of the exhaust system. If this is the case, it means something has gone wrong with the car that makes the engine or transmission computer think it needs to run a really conservative calibration to protect the powertrain. He is a graduate of Michigan State University and holds a Bachelor of Arts in advertising. I don't understand why it drove perfectly that one time and I can't recreate it now. Any check engine lights? There is a shudder under acceleration that starts at 30 mph and will continue to 40 mph were it goes away. We are possibly buying a saturn outlook with A good scan tool might reveal something but it may require that the car be hooked up to diagnostics while the actual event is occurring, so that data from various sensors and modules can be captured in real time and analyzed by a skilled mechanic. In any case, you will likely find the problem relates to an imbalance in fuel and air mixing in the chamber. As others have said, lack of fuel. If it's been sittting, you may have condensation and/or rust in the tank making it's way through the system. I assumed that once the ECU detected that one of the sensors was faulty it simply relied on the opposite for fuel trim corrections/adjustment. He has also studied martial arts since 1990 and has worked as a licensed security specialist. When the engine is first started cold it is running open loop and the O2 sensors aren't used at all. I would suggest having a professional from Your Mechanic come to your home to diagnose your mass air flow sensor. It may not display this or other websites correctly. carbon out of everything especially the ports If you let your fuel injectors continue to be dirty, then it will impact how much fuel gets injected into the chamber. Drive it long enough that way & a CEL will appear, prob. How difficult on the 3.5 V6? The throttle position sensor monitors the throttle valves position and then relays this information to the engine control unit. Getting ready to change the up-line O2 sensor(s) and then maybe the MAP if the O2s dont work. My 2008 nissian Altima is hesitant when going up a hill or accelerating Ive changed the fuel pump the air filter and the air intake hose but it is still having the same problem, We found my car was hesitating and stalling when I took off from a stop or went up a hill because after 24 years, the motor mounts were worn and that caused rubbing of the wire harness and some of the wires had the insulation rubbed off, causing shorting. fuel filters, etc. With his money, I would think he would be more of a Bentley man. Why, if you think it through, should it be otherwise. My mustang hesitates 40mph and gives me hill starts assistant not available ! When you go to step on the gas pedal to accelerate, you will suddenly feel like the power has been lost in the engine for a couple of seconds. . Standard mailing time from the win date and the date received, will depend on the winners geographic location.14. 1) Bad Throttle Position Sensor The throttle position sensor monitors the throttle valve's position and then relays this information to the engine control unit. This comes and goes but happens enough that I have a service appointment scheduled for tomorrow with the dealership. I could take my foot off the accelerator and then reapply and my vehicle would work fine then. 2023 CarGurus, Inc., All Rights Reserved. 3/4 i actuall had 2 fuses blown from a short in the wiring harnes the other was TRS CC Bad spark plugs, sensor failure, and bent valves can all cause engine loss of power, thus . Now, I do know that If the car is traveling 40 mph and the speed suddenly falls while the engine continues to rev, the transmission probably is to blame, especially if pushing the accelerator has no effect and the car continues to slow down. Started 4 hours ago, By the heater is only used during initial engine start up. My car was jerking as well. Still at it. Billy from United States 7 years ago BI Comment Same issue here 17 reports Let me know and I will post them. If it happens mainly with acceleration, even slight acceleration, you may have a plugged catalytic converter. Thanks to this article I will also try cleaning the MAF but It still does it with the air cleaner disconnected but it is worth a try. Most of the time if the vehicle is running fine it comes on from low brake fluid or a failing wheel speed sensor (https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-wheel-speed-sensor). I have a 2005 Ford Focus Wagon and it does the same thing! Just a hunch. Im not sure I understand the question. The children are from the small town of Bad Arolsen in the central German state of Hesse, and are reportedly in the 10th grade, meaning they are aged 16 and 17. if I was guessing & it had no code I would run some Techron through the tank. Specifically, it will tell you what your TPS values are, then you can compare that to what they should be. The hissing sound you are hearing is most likely a source of a leak in your cooling system. If your car is moving at 40 mph but is unable to accelerate any further, the transmission probably needs service or replacement. It doesn't happen every day but more days yes than no. The engine control unit depends on the MAP sensor to determine the engine load. Car runs great between 0-40 mph and from about 50 mph on up but the car jerks while eccelerating between about 40 - 50 mph. plugs are OK. Sorry, I find it a bit hard to accept that a defective MAIN O2 sensor in an engine with TWO sensors, would result in a lean misfire. My Nissan Macra car hestates when pressing the gas pedal, it acts like losing the power! Hi all. hesitates around 40 to 60 mph. Can you help diagnose? If the oxygen sensor is not working properly, then the proper air and fuel mixture cannot be achieved.