We both feel that the the low range fuel pressure sensor reading a constant 5 volts is worth investigating, but as we can actually find a low pressure sensor (under the bonnet) we are none the wiser. The misfire code will indicate that something is not right with the engine. Changed the crank sensor the other day as a precaution as the last two cars I have owned have needed crank sensors in mid to later life. Magnus is the owner and main author of Mechanicbase. One of the conditions that is required to set the code is a fuel . No PCM codes so I'm using the car to see if anything changes or codes appear. Older cars use a distributor to distribute the spark to all the spark plugs, which are powered by an ignition coil. 1. Misfire Codes: A bad timing chain tensioner or guide also causes the check engine light to illuminate. In this video we show you how easy it can be to diagnose a misfire on a modern engine with the right tools.Latest Ford Parts:Ignition Coil (2011-2016)-https:. The 74-page lawsuit was filed by five plaintiffs, Robert Reed, Stacy Coppock, Craig Morford, Kelli Morford, and David . This revealed a short circuit to earth for one of the HP fuel rail sensor wires. You can check for vacuum leaks by gently spraying a flammable spray around the engines intake manifold while the engine is idling. Some of the most common causes of engine misfires are bad spark plugs or a bad ignition coil, which can be relatively cheap to repair. Additionally, turbocharging and direct injection assist the 3.5 V6 in remaining fuel efficient and emission-free. Ecoboost 1.0 - Difference Between 100Hp And 125Hp Version ? The function of the spark plug is to ignite the air-fuel mixture in the combustion chamber, and if there is something wrong with the spark plug, it will not ignite, and a misfire will occur. Some F-150 owners have complained of a mysterious misfire on these engines. As a result, symptoms such as fault codes, a rough idle, and stuttering may occur. In my case cyl 2 4 6 8 on a dakota 4.7. I just realized that 1999 toyota Camry is running on 3 cylinder By reading your article I'm without any doubt that you're a professional. The lawsuit alleges that the leaking of . However, it is a much simpler job than changing the spark plugs. Aug 11, 2020. It is, however, inherent in owning a twin turbo, direct injected engine. If your car's check engine lights come on and stay on, more than likely the camshaft sensor is bad. Started Thursday at 09:49 AM, By I thought it was misfiring or driveline related. Any thoughts, is the fiesta 1.0 ecoboost prone to wiring loom faults, ecu faults, multiplug pin corrosion, water getting places it shouldn't? Were the loom turns behind the engine there is a metal bracket which supports the connectors to the two oxygen sensors. or my ECU ? Parts cannon loaded and ready -- Customers paying -- Fire at will !! Identifying these issues can be a little hard. Fuel Injectors Can Get Clogged. This oil eventually cakes onto the intake valves as it travels through the intake tract. i have hyundai accent 2012 model ,manual gear.my car RPM fluctuates even after i changed my coils ( 3 coils are good and one coil current was leaking so i changed only that coil),plug ,air filter etc.kindly suggest what is the remedy for this problem. There is a gasket located between the cylinder head and the intake manifold called the intake manifold gasket. Remember, the root cause of ecoboost misfire is the condensate buildup from the intercooler. December 3, 2020 Ford EcoBoost problems have caused a class action lawsuit that alleges 1.5-liter, 1.6-liter and 2-liter EcoBoost engines allow coolant to leak into the cylinders. You may or may not be able to monitor High and Low side Fuel Pressure readings, actual and desired. To fix engine misfires, you need to read the trouble codes from the engine control module and continue troubleshooting from there. Its best to diagnose and repair the issue as soon as possible. Causes & How To Fix It. You can also open the hood of your car and watch the engine idle. Once at normal operating temperature the car drives perfectly with both fuel trims very close to zero, although there is a power dip flat spot at full throttle 5500rpm which is odd, e.g. All Rights Reserved. Is normal that engines sound smoothly when there's misfiring in all cylinders? It gains 375-450 horsepower in the majority of models. Two of the issues listed above may not even be considered issues. Condensation can build up and be trapped in the intercooler on certain F-150 models with the 3.5L EcoBoost V6. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. 2.7 EcoBoost stumble on highway acceleration. The plugs should be fine, then. I would like to congratulate you on the simple way of explaining this article on misfire troubleshooting. Due to the high turbo boost pressures, spark plugs and ignition coils are subjected to significant abuse. At the moment I can only comment on two of your points. Additionally, the use of twin turbos provides an abundance of tuning potential for those looking to get the most out of their engines. Here we will look at what you need to know about engine misfires. In fact, nuzzle 2 & 3 does not bring up any sign it is OK when removed from the plug head to the nuzzle. Hello allhopefully I'm not regurgitating info herebut since my searches led me to different bits and pieces of my solution, I figured someone else might benefit from it all being condensed into one place. Symptoms The signs of a leaking turbocharger system start with a lack of power or random misfires. You cannot paste images directly. Codes P0089, P0087 and P2626 were showing but no engine check light. You earlier indicated that your reservoir tank was "lowering as usual" or similar to that wording without me going back and checking. I used a flat blade screwdriver behind the coil to help wiggle it a little to get it out. The engine in modern cars uses many sensors to measure everything in the engine to make them as efficient as possible. What else can I do??? <>Avoid over tightening the bolt to prevent from cracking the plastic ignition coil housing. Hi guys Seriously you need to find a different garage. Zain. Again, be careful that you dont apply to much force and break the plug. I don't know what Scan Tool you are using but FORScan is your best bet for Live Data on any Ford car. I also attempted to clear the keep alive memory by disconnecting the battery for an hour, don't know if this worked but it did zero all the average fuel economy data. How to Spot Carbon Buildup. Although most modern cars use an electric fuel pressure sensor, youll want to confirm the results with a manual fuel pressure gauge, because an electronic sensor can fail. Great helpfully web site. But, if the wastegate or bypass valves are leaking, you might not hear any noise. (Heres How To Fix it), 7 Best Spark Plugs Review & Buyers Guide, Car Losing Power When Accelerating? The wideband front O2 sensor should show a Current of 0 most of the time under constant or no Throttle openings. NQbbe My guide has information on the top 9 most common F150 PCM problems and their symptoms. Glenn hastie Maintain the Ford EcoBoost engine properly, and it will almost certainly reward you with a dependable, enjoyable driving experience. The carbon deposits can cause un-even amounts of air to enter to cylinders. Terms of Service - To find out if your engine has low compression, you need to do a compression test and compare the results to the manufacturers specifications. Then, you want to look for vacuum leaks and cylinder compression. This is a repeat of a problem I had about 2 years ago which was never diagnosed but cleared itself which is always a bit unsatisfactory Initially the symptoms were very noticeable and made the car difficult to drive, then progressively improved during the 10 mile journey home and are now just annoying. If your car engine is misfiring, it is important to find out the cause and fix it as soon as possible. However, it is entirely possible that this is simply because the F-150 is the most popular model equipped with the EcoBoost engine. Its my first scan tool which has been useful but is limited by my knowledge and the small screen. If you have any of these symptoms, it could mean the camshaft position sensor needs to . In the case of a misfire a P0300 (random or multiple cylinder misfire), or specific cylinder P0301-P0306 should have triggered. When it reaches normal speed it quit shaking. Hi I have a 61 ford falcon 6 cyl has a miss fire under load new coil, plugs, wires points cond, dist, all cyls fire, My 206 puegoet starts up fine from cold drives 100 percent problem is when it gets hot will drive it when I switch it off and start it up get miss fire and loss of power so I have to switch it off and start it up after a few tries it's gets back to normal even though the car is hot. RELATED: 8 Causes of Low Compression in a Car Engine (& How to Fix). Additionally, Ford redesigned the timing chain in response to concerns about the previous designs reliability. On naturally aspirated engines, spark plugs frequently last over 70,000 miles, while ignition coils typically last about twice that. Unfortunately, low compression problems are often caused by worn parts inside the engine, which can be very expensive to fix, so youll want to inspect the other possible causes first. Some believe it is due to insufficient maintenance and oil changes, or to the use of 20w oils, which are too thin for the engine. Ignition components can produce a wide variety of symptoms and drivability issues, so dont overlook simple spark plugs or coils. I did the thottle position sensor reset procedure and that helped for about 2 days. I finally adjusted the float screw anti clock wise and my problem was solved. Its plastic, so you dont want to pry on it or you may break it. Were always looking for new content to share with other Ford Maverick truck enthusiasts. If you notice any of the signs or symptoms of a misfiring engine, get them checked out by a professional as soon as possible. It suddenly lost power like it wasnt running on all 6-cylinders, and the check engine light was blinking. Had the DTC read as P0301 (#1 cylinder misfire) and went to my local Ford dealer, bringing a copy of Ford TSB 12-10-19. Copyright text 2021 by driveceladon.com. Every 10,000 miles, our twin turbocharged 335i with the N54 engine requires new spark plugs. The car is my daily driver and I'm not necessarily looking for an . The 3.5 EcoBoost engine from the first generation utilizes only direct injection (DI), which means fuel is sprayed directly into the cylinders. Update, car is back from the garage without a diagnosis. Ford addressed this issue with the second generation 2.7 EcoBoost by utilizing port injection. The Escape is a hot mess. Repair this yourself or, if you prefer, have it done by a repair shop. Did you fit standard OEM? We are very familiar with this coming from the BMW world. Within about 5 minutes of leaving the pump the engine was struggling. Last thoughtI've still yet to test it towingneed to know whether I'll still have to play the game jumping between 4th and 3rd depending on the incline. Woww wow wow great article! Yes it sounds like lean mixture caused by either low fuel pressure or vacuum/boost leak. Read more: 8 Symptoms of a Bad Fuel Injector (& Replacement Cost). Car wont move after CV Joint replacement. Jiffy Lube Vs. Valvoline Oil Change: Differences & Which Is Better. May 9, 2021. READ MORE: 15 Types of Car Sensors (& What They Do). I had a hard time describing what it was, but now this is the clearest description of . You can do this with either a compression tester or a leak-down tester. However, be very careful when doing this and have a fire extinguisher ready. A high-quality shop vac and walnut media shells are required for this job. Another subject well delve into. Low fuel pressure can be caused by a faulty fuel pressure regulator, a faulty fuel pump, or a clogged fuel filter. Hesitation everytime I get into the throttle. Only history I have is the truck has had all six ignition coils replaced . What are your thoughts on the 3.5 EcoBoost? Hi my name is Victor I have a 07 Pontiac Grand Prix V6 I am getting a code low sufficiency threshold have changed wires plugs coils and it runs fine and when I put it under a load start start to run rough so what clean the injectors again it runs fine until I put under load what is the problem, I replaced both coils 8 spark plugs and wires still running bad checked my ekg valve it works motor still shakes and body as well could it be a faulty fuel injector I need help. Replace oil cap. The plugs were changed at 40k as I was aware of a slight hesitation back then, no improvement, the car is at just under 50k now. Paste as plain text instead, The dip is so fast the computed pressure in kPa doesn't mirror the raw voltage, but both their trends look noisy. 1. engine may exhibit various engine misfire symptoms accompanied by diagnostic trouble codes (DTCs) P0300, P0301, P0302, P0303, P0304, P0305 and/or P0306 stored in the . good article but didnt cover a p0300 with misfires on all cylinders on 1 bank of a v8. 5. less than 5-10 Deg C. The PCM was changed by the main dealer back in May, I suspect a couple of minor miss fire moments since but the jury is still out, particularly given the warm summer weather. Vacuum leaks are a common cause of an incorrect air-fuel mixture and are fairly easy to check, so you want to start there. Since the 3.5L Ecoboost in my Expedition has 79,000 miles on the original spark plugs, I decided to replace all (6) spark plugs with new ones. Here's my top pick motor oil for the Ford EcoBoost cyclone engine. Well discuss some of the most common issues with the Ford 3.5 EcoBoost V6 in this article, as well as its overall reliability. 3.5L EcoBoost - Cold Start Ticking/Tapping Or Rattle Type Noise - Built On Or Before 31-Oct-2019 20-2315 14 September 2020 This bulletin supersedes 20-2191. if everything is working correctly. If the timing chain completely fails, additional damage to the 3.5 EcoBoost engines is possible. Here are some of the symptoms of a bad VCT solenoid: 1. Youll also want to inspect the spark plugs and ignition coils. Privacy Statement - The known common problems of the Ford 1.5 Ecoboost engine are: The Problem Of Overheating Has Been Exceeding. I knew my Metro had a burnt valve and low compression, but I would not call that a misfire, since the fuel is burning fine, just leaking into the exhaust and delivering less power. The majority of 3.5L V6 EcoBoost engines should have no significant issues reaching 200,000 miles or beyond. If a sensor is failing or a sensor detects that something is wrong with the engine, it sends the information to the engine control module. I used a small screwdriver to press down on it as I slid the plug off. Although the engine appears the same on my car there is no sensor on the low-pressure side fitted. John, thanks for your reply. Update, still not fixed, Ford Main dealer have discussed with Ford UKand both are unable to offer a diagnosis with any confidence. New plugs areNGK Spark Plug SILZNAR8C7H (93593) same NGK part number as the originals. However, using PI has a few additional benefits, most notably assisting in the prevention of carbon build-up. Push a new spark plug into the spark plug socket. First check all ground connections are clean and tight. Started 4 hours ago, By Carbon tracking is where the spark fires between the top of the plug and the base, across the ceramic shell. Ford has also issued bulletins, indicating that they are fully aware of the timing chain issues. Remove the dipstick and place it on the clean rag to avoid contaminating dirt and debris. Clues so far is that it doesn't like colder temperatures e.g. General discussion on 2009 - 2014 Ford F150 truck. I changed my plugs and gapped them to the .028 and replaced the boots about a month ago. The truck is setting p0302 and p0305 under heavy acceleration. I have not noticed any slack in the joint. What do I do? Even if you think it will be very expensive to take the car to a mechanic, it can actually sometimes be cheaper to get a proper diagnosis rather than replacing fully functional parts. If youre running a tune, making mods, or driving the 3.5 EcoBoost hard, the lifespan of the ignition components can be significantly reduced. It can also seriously damage your engine. It can also be caused by fuel-related issues such as a faulty fuel injector or a bad fuel pump. If you find trouble codes on an engine sensor or low fuel pressure, youll want to start the diagnosis from there. 9. Had a slight misfire so I changed Spark Plugs and Coils. This is why you HAVE TO DRILL the 1/16" intercooler weep hole. So far I filled the the tank with premium fuel and added an injector cleaner, no change after 100 miles. When I first purchased the fuel mileage was horrible but my smiles per mile was up, now the best Ive seen from the lie-o-meter was 19mpg on the highway and heck I still smiled.WTH..lol. I turned around and headed home, and after a short distance, the check engine light stopped blinking, and the truck seemed to run smooth again. The most common cause of an engine misfire is a bad or failing ignition coil. Is there any cheap way to improve compression or get rid of the code? Misfires Are More Common Than You'd Think. Additionally, the 3.5 EcoBoost may generate the P0016 fault code, which will illuminate the check engine light. Need some advice here, I have a 2015 F150 3.5 Ecoboost. These are plastic components, so be careful that you dont break them. I have a golf 6 TSI model 2010, I changed new spark plugs, ignition coil and spark plugs cables but the car still misfires at times but not always. Matilda Magnetic build 2019 6.5' bed crew cab fx4 heavy tow.. Do Not Sell or Share My Personal Information. A blown head gasket can cause low compression. Hi all, my 1.0 ecoboost has recently started to misfire or hesitate under light throttles. The fuel idea has crossed my mind, the car is usually filled with regular supermarket fuel, however, on this occasion I had just filled up with fuel from one of the major UK fuel and oil brands, still regular unleaded E10. 2015 ECO 3.5 Misfire-Tried everything, I think. MechEng, Turbo engines do require some additional maintenance, but we believe it is worthwhile in the long run. Kinda forgot the power the 3.5 eco boost had when it was running rightat least no cops were nearby lol. Additionally, direct injection causes carbon deposits on the intake valves, which can cause drivability issues. With a false high fuel pressure this leads to lean running and the fuel trim controls ramp up to compensate. in both cases, the engines were significantly under the mileage recommendation to replace the spark plugs. Has been a great explanation about the theme. I have done plugs and coils as well, even new throttle body. As for these Ford 3.5 EcoBoost, problems result from the engine using a direct injection fuel system and being twin turbo. This makes the 3.5 EB an excellent engine for towing and fun around town without requiring full use of the engines RPM range. Powered by Invision Community, DISCLAIMER: fordownersclub.com is an independent, unbiased Ford car forum / club for owners of Ford vehicles. So far Im very pleased with my eco as its made me grin when ever I squeeze the smile pedal and if Im not careful my tires or me wont be when replacing is needed. Clear editor. Not too shabby in terms of longevity. Inject not getting fuel , so cylinder does not fire , so get misfire code. If the misfire is specific to a cylinder, it may display a check engine light and a DTC such as P0301, P0302, P0303, P0304, P0305 or P0306. Glad you found something that works. Ryan jones Here is a more detailed list of the most common cause of engine misfires: 1. I thank you for making my life so much easier I'm going forward finding my problem. Spin in the spark plug a few turns by hand in the clockwise direction to prevent it from becoming cross threaded. Contact Us - If the fuel injector injects the wrong amount of fuel, it will cause the engine to run rich or lean, which can lead to engine misfires. Thus until reading your wonderful explanation, I could not figure out why my computer was calling my burnt valve a "misfire", which I think is a bit misleading of OBD2. If youve checked all the things above, but still cant figure out whats causing the misfires in your engine, it might be worth taking the car to a professional mechanic instead. However, because carbon build-up occurs over time, it is frequently difficult to detect. Automotive Performance, Tuning, & Modification. If you dont know when you last changed the spark plugs, you need to check your service manual and replace them if necessary. Need some advice here, I have a 2015 F150 3.5 Ecoboost. The Latman Repair Urgency: Fix this code immediately (same-day if possible) to avoid ignition failure, catalytic converter damage, and dangerous conditions. If your vehicle idles roughly, stalls frequently, has a drop in engine power, stumbles frequently, has reduced gas mileage, or accelerates slowly, these are all signs your camshaft position sensor could be failing. You can either get one yourself, or go to a mechanic and borrow their diagnostic tool to read the trouble codes from the ECM. Declan19971 but I don't feel or hear any misses . The carbon build-up causes uneven combustion, and it messes up the air-fuel mixture. Engine misfires are serious. Yes. Earlier generations of gen 1 engines encountered issues with timing chain failure and carbon buildup. Ford 1.6 Inline-4 Timing Belt Change. Started February 9, By VVT has the ability to generate more power or save more fuel depending on the phase of the camshafts. The socket should have a rubber insert or a strong magnet to securely hold the plug in place. I took it back home since I didnt have $3000 at the time and on a gamble went down to the auto parts store and bought the tools and spark plugs to swap the plugs out. Before delving into 3.5 EcoBoost problems, its necessary to establish some context. Some vehicles have a separate ignition coil on every spark plug, while some cars have one coil pack with an ignition wire to each spark plug. I do see codeB10EA from the positive temperature coefficient heater sometimes but have assumed that cant be related. Overly rich running engine. OEM COILS - Keep in mind no check engine light just a slight miss under light loads and typically above 60MPH (1200-1500 RPM) Didn't solve the problem, re did the process . When I got home I scanned the truck for trouble codes, and discovered these codes: P0300 (Random/Multiple Cylinder Misfire Detected). Double check that the spark plugs are tight before moving on to the next steps. Rather than that, they are a few of the most frequently encountered issues when something goes wrong. Youll have to push down on the gray tab to get the plug to connect from the coil. Having said that, well delve deeper into these 3.5 EcoBoost issues below. Early EcoBoost engines were also known to catch on fire, leading to a 2012 recall and "stop driving" order from Ford. Then, go backwards to cylinders 2,3,4,5,6 on the driver's side. Before we begin, lets jot down a few quick notes. If your car engine sounds unusual, its possible that your engine is misfiring on every cycle. Turbocharged engines place a great deal of strain on the ignition system, owing to the incredibly high cylinder pressures. Acts like it doesn't know what gear it should be in. The plugs have been used for no more the 2k miles. As a result, the cylinders of the 2.7 EcoBoost may experience inconsistent air delivery due to restricted airflow. This can lead to a variety of engine performance issues and can even lead to serious engine damage if left untreated. Jun 30, 2021. Check light blinking, car acceleration slow. Vehicle does not drive like it used to. However, finding these vacuum leaks is often quite easy and we will talk about that further down in the article. Always starts and idles perfectly, even passed its MOT. I haven't done anything with the turbo bypass valve so far assuming that at these very light throttle loads the turbo can't be contributing much if anything. Hi, Magnus i read your instructions, i own a vw tourage 2008, according to the trouble codes i got from dtc the engine has a misfire on all 6 cylinders, and random misfire, one thing that i wonder is that the engine sounds smoothly well tuned, the check engine light is on, I'm replacing the spark plugs they are dirty and according to the a page that i found in Google the gap should be. 3. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates. Like you I thought spark plugs and changed them early on but sadly no improvement. Fortunately, a set of six Ford 3.5 spark plugs typically costs between $40 and $100, depending on the source. Tighten the bolt in the clockwise direction with the 8mm socket and a 1/4 drive ratchet until it is snug. I wasn't very succinct with my summarybut yes, I agree fully with Bravo and Whoand yes, when I have it to do again, I'll never own another boosted motor. I did not find any evidence of carbon tracking on the plugs I removed. Low Engine Compression. I would start with checking for any leaks around the intake and connect a fuel pressure gauge if possible! These are the most common symptoms of 2.0L EcoBoost coolant intrusion, but not all of them. Another possible problem that can cause misfire fault codes on only one side is low compression. Please register or login to enable Dark Mode. OK ForScan up an running and after much testing I can see the fuel rail pressure sensor raw voltage signal intermittently dropping to zero volts for a few mili-seconds then recovering. The most common code you will see is the P0300 code, along with a code like P030X. But how do you tell if your engine is misfiring, and what could be causing it? Ignition coils should last approximately twice as long. srpocd25 Leave a comment and inform us! . Verified plugs and wires by swapping #1 with #3. Additionally, Ford did an excellent job with the second-generation 3.5 EcoBoost in addressing some of the issues. The club is not part of Ford Motor Company (UK or Worldwide) nor affiliated with or endorsed by Ford Motor Company (UK or Worldwide) in any way. Your link has been automatically embedded. Additionally, while youre in there, consider replacing a few other small items. The worst condition of exhaust and converters. The Ford 3.5L EcoBoost engine can power several models, including the Ford F-150 and the Lincoln Navigator. There is a red locking tab on the plug: If you get a vehicle in that is not generating enough boost, don't automatically assume it is the . This misfiring of the Ecoboost leads to rough idling, stuttering, and fault codes. Although this is a very rare occurrence, it is critical to repair the timing chain promptly if problems arise. With the retaining the ignition coil plug unplugged and the retaining bolt removed, you can now pull the coil straight out of the hole. Every engine suffers from some degree of oil blow-by. Was told it might be the fuel sending unit . To missmy06 I havent seen a positive post out of you yet and Im sure any dealership would be happy to trade in your current truck for another 06 and down and probably the finances would not change so go for it. Started 2 hours ago, By Its a simple and inexpensive repair. I have a 2014 chrysler town and country van 3.6 engine number 3 cylinder misfire changed coils, spark plugs ,fuel injectors compression 130 # wires good to and from injectors good,ohlms across injectors,air filter good, intake gasket good added heat to gas tank. This is what causes the misfire. I think the Fuel Pump Module is at the Fuel Tank, I'm not sure where it measures the pressure though. What Happens When You Put Too Much Oil in Your Car? To be honest, this is mostly here because weve run out of other topics to discuss regarding the 3.5 EcoBoost. The misfire can come or go depending on what is going on with the ECM. Ignition coils have a life expectancy of 25,000 miles if were lucky. Those idiots told me I needed a new charge air cleaner, intercooler, possibly new turbochargers and whatever it was would be like $3000. In any case, the issue at hand is one of timing chain stretching. Best regards, It also causes the plug to misfire. Ford, on the other hand, took it a step further by offering a 647hp variant of the legendary Ford GT. Avoid over tightening the new spark plugs to prevent from stripping the aluminum threads. Rotate the ignition coil back and forth a few times to help spread the dielectric grease. Carbon build-up is primarily an issue with first-generation engines. This includes misfires, power loss, and a rough idle, among other things. Cookie Policy - they then suggested that I replace all plugs and boots and get an induction flush. Remove the plug on the ignition coil of the cylinder youre working on. Yeah the misfire is only on cylinder 4 according to the AP and about 2 weeks ago it began. Compare the results with the manufacturers specifications, and if the compression is low on a cylinder, you need to inspect the engine parts such as the timing belt, piston rings, valves, or pistons. jsk The car has run perfectly all summer but in the last couple of weeks the fault is back.