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How does the car's ECU detect a misfire?

This comes directly from this web site: http://www.obdii.com/articles/Onboard_Diagnostics_Demystified.html What it says, is that early OBD-II systems could not detect misfires, but since then a few ...
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14 votes
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Can a bad timing chain result in only a single cylinder misfiring?

"Can a bad timing chain result in only a single cylinder misfiring?" No it cannot. It could be a Bad ignition coil on that cylinder, if there is a coil for each cylinder swap it from another ...
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14 votes
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Volvo engine parts

What you have circled are the connectors for the fuel injectors (and obviously the fuel injectors are underneath of them). They have seals which protect from moisture, dirt, and debris, so in most ...
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12 votes

How does the car's ECU detect a misfire?

Engine misfire can also be detected by looking at the coil voltage just after the plug is fired. When the fuel/air mixture actually ignites there are lots of ions and radicals floating around. This ...
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9 votes
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Can a crankcase venthilator hose being off cause misfiring?

Yes, the air that is passed through the crankcase ventilation system is metered before it enters the ventilation system. If the pipe is off, un-metered air will be allowed in, which will cause a weak ...
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7 votes

MAZDA 3 2006 (UK) - poor acceleration then takes off at 3250 revs

My gut says it's likely to related to either a dodgy throttle position sensor or a faulty air mass meter. Whilst it is reporting no errors, it's worth doing diagnosis such as resetting the throttle ...
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6 votes
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Will Driving 100 Miles With a Misfire Damage My Car?

You should be fine. Though I would recommend unplugging the connector to fuel injector #7 to minimize the amount of unburnt fuel that makes its way to the catalytic converter.
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6 votes

How does the car's ECU detect a misfire?

Variations in current drawn by the "high-tension" (HT) coils can also identify misfires to the engine ECU. This is one reference that I found to back this up AutoTap: Analyzing Ignition Misfires (...
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5 votes
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Car shaking on startup

Most of the time on the Mazda3 the blame is defective engine mounts, they are too soft. Its the upper mount that's the prevalent one. There are aftermarket replacements available. Now there are a ...
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5 votes

Cause of limp mode in Vauxhall Astra which ECU code is relevant?

Essentially you have put 10 milliliters of oil in your gastank I have done this before with more oil than that on accident into my truck. My solution was to fill the tank to the top and dilute it as ...
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5 votes
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The Mystery of the Misfiring MINI

It was the high pressure fuel pump. After letting it sit overnight, the dealership was able to reproduce the issue and replaced the pump under the extended warranty. The car is driving like it did ...
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5 votes
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Can lack of oil cause P0300 Random Misfire?

There's nothing that detects whether the plugs are actually igniting the mix evenly, it is inferred from the acceleration that the crankshaft undergoes each time a cylinder fires. There's plenty of ...
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5 votes

Spark Plug porcelain fell into cylinder

While it could be an issue for the porcelain to drop into the cylinder, it's not going to make your car run bad. Either there is damage to the engine or components and the engine will run crappy all ...
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4 votes

How do I fix my XF125GY 4-stroke engine misfires?

Resolution 1. Drain your oil The reason you are having the issue is too much oil. You overfilled your crankcase and now the oil is coming out of your PCV (positive crankcase ventilation). Your PCV ...
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4 votes
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VW Golf IV Possible Engine Misfire

It means that your camshaft position sensor or crank angle sensor is faulty. Either because they are actually faulty, or there is a wiring problem. Clearing the code won't do much. The symptoms of a ...
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4 votes

Are there varying degrees of engine misfire?

Yes, misfires vary in their severity. However, it is worth mentioning that your reader may be displaying old codes, or codes which were triggered by abnormal engine activity that is no longer present....
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4 votes
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A/C Temporarily Cures Low, Hiccupping Idle

When the throttle body becomes a little worn, it is possible for the butterfly valve to close too much for a steady idle engine speed. The ECM then tries to compensate by opening the IAC more than it ...
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4 votes

A/C Temporarily Cures Low, Hiccupping Idle

Your CPS code won't explain the hunting idle; the symptoms point to a lean air-fuel mixture: it doesn't stutter at low idle with the engine cold because the fuel management is designed to enrich the ...
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4 votes
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08 Silverado 5.3 rough idle and dark cold start exhaust

First of all, the 5.3l engine (could be all of the Vortec LS engines, don't know) is thirsty. It drinks a bit of oil. Be aware you could be looking at up to 2 quarts between oil changes. I don't know ...
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4 votes

Corsa D Stuttering Accelaration with Malfunction Light flashing

A flashing check engine light means you have an active misfire. Driving your car while misfiring for an extended period of time can cause damage to your catalytic converter, so try not do do that. ...
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4 votes

Cylinder misfire after leak down test

You don't say why you needed a leakdown test in the first place. If you rotated the engine by hand in the opposite direction that it normally runs and it has a timing belt then it is possible that the ...
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4 votes
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What is wrong with my Ford Focus? Missfires and more!

My first questions for you? Isn't that a new car, still under factory warranty? What did the dealership tell you? (What year is the car? what is the mileage?) If not, that sure looks like a wiring ...
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4 votes
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Meaning of Timing valve is open

The P0018 code is related to your cam and crank showing incorrect timing There are two sensors involved in this error. Cam Position Sensor Crank Position Sensor These two sensors detect the angle ...
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4 votes

Can (possible) exhaust system damage cause random misfires?

If the muffler hitting the railroad tie stopped the car, you very well may have snagged something loose. Visually inspect your exhaust and pay special attention to the O2 sensors, they may have been ...
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4 votes

Astra MK6 - when warm, rough idle and shudders while accelerating

I don't know that particular car well, but maybe a vacuum leak? Perhaps it's at the intake manifold, and worsening as the parts warm up, expand, and mating surfaces change shape?
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  • 41
4 votes

Highlander Hybrid losing oil/coolant

I don't recommend driving it further; you risk packing up the cooling system if oil makes its way there. You might want to invest in some quick tests before you buy anything: You need to confirm if ...
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  • 39k
4 votes

Black Spark Plugs that Clean Themselves

I've seen this behaviour on a car with a hairline crack in the fuseboard. The result was that sometimes the car would run beautifully and sometimes it would all but die and bog down on the throttle. ...
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4 votes

Weird object in cylinder head preventing spark plug install

It appears the threaded portion of the body has broken away from the body itself. The split would have occurred at the point where the image below points to as "spark plug gasket". This could have ...
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4 votes

Pros and cons of driving a vehicle with a misfiring cylinder

I can relate a story from my own experience with my daughter's car. Turns out it had two bad ignition coils that caused the engine to misfire when it was raining. Did she stop when the check engine ...
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4 votes
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Can swapping ignition coils fix a cylinder four misfire?

It normally wouldn't, however, I'm thinking the problem might have been the wiring connector to the coil wasn't making a good connection (or possibly causing an intermittent connection), which was ...
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