23
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 variations on the theme have been implemented. The basic idea is that if a cylinder fires, it gives a kick to the crankshaft causing a slight variation in crank ...
12
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 provides an easier path for electricity from the coil. If the mixture does not ignite for any reason the resistance is extremely high. An observant auto tech ...
10
I observed this same situation in my 1997 Integra back in the day. If you look at the summary on Wikipedia, you can see why the oil pressure is critical to VTEC:
At the switch point a solenoid is actuated which allows oil pressure
from a spool valve to operate a locking pin which binds the high RPM
cam follower to the low RPM ones.
So, without ...
9
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 mixture and therefore possible misfiring.
7
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 position (sorry, I'm not sure how this is done on this car) and checking things like coolant temperatures reported by the ECU against guestimated values.
If it ...
6
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 (archive)
5
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.
5
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 few other things that it could be.
Massive air leaks, check the EGR valve. It would be a good idea to do a smoke test on the intake and engine. The test will ...
5
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 much as possible. This worked fine for me and I had no ill effects that I am aware of. The truck passed emissions after that and I have had no maintenance ...
5
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 when I bought it two years ago. No more trouble starting, no more stumbling when accelerating when cold.
Thanks to everyone for your suggestions!
4
There are two things I can think of for you:
First - Are you sure you changed the plug/wire for the #4 cylinder? I know this sounds elementary, but you never know. When you pulled the plug out, did it look wet, or tan as it should? If it was wet, you've changed the right plug. If not, you probably want the middle cylinder (assuming a v6 engine) on the other ...
4
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 vents your crankcase on the valve cover. It's the big hose attached to it. Oil gets into that hose that attaches to your airbox between the air filter and the ...
4
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.
For example, if the vehicle were filled up with a bad batch of fuel that had water it, it could temporarily cause misfires. The fault codes for misfires ...
4
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 AFR while the engine is warming up (aka cold-start enrichment)
turning the AC on helps because it induces an additional load on the engine, which makes it ...
4
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 bad cam or crank sensor are usually rough idling, difficulty starting and misfiring. Which makes sense, because your ECU gets wrong information regarding the ...
4
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 is designed to under normal conditions. This can cause stalling and unsteady idle. There will be a screw on the throttle body that allows adjustment of ...
4
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 exactly what the issue is, but it does have a bit of an oil control issue whether it has to do with leakage or burning. My '06 is this way. It has never ran bad ...
4
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.
Studdering/juddering or however you want to describe it is also a definite sign of a misfire. Suspecting the coil(s) or wires is good, and that should be your ...
4
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 valve timing may have jumped. You would have to remove part of the covers and check that all cam timing markes line up as per the manufacturers specs. If its ...
4
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 issue to me, based on that tachometer dropout. Loose ground? Intermittent short or disconnect to the crank (and / or cam) position sensor? Note the crank (...
4
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 of rotation of each shaft and when they fall out of tolerance in timing, you get this error.
There are multiple reasons why your crank and your cam(s) may be ...
4
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 jarred loose.
I wouldn't replace the fuel injectors just yet, but do visually inspect the engine bay, and for sure reseat the fuel injectors' connectors. I ...
4
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?
4
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 there is loss of coolant through the engine
A few options here:
perform a compression test to see if a head gasket or cylinder head is compromised
perform a ...
4
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 been done by over tightening the spark plug. The insulator has pulled out from the body and the threads are stuck in the head. You'll need to remove the threads ...
4
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 things that can cause uneven firing - vacuum leaks, variations in mixture, uneven fuel pressure, though anything like, say, low compression will soon be resolved ...
3
There appears to be a similar case on the Cobalt forum, where compression test figures are reported to be around 220 psi, roughly double what you're reporting.
If this is the case for your vehicle, it would seem that the problem is related to a lack of compression and not fuel, air or spark.
3
Just had the EXACT same thing happen to my 2004 Accord EX 4 cyl/auto trans. . Accelerating with A/C on... car began cutting out. Immediately turned A/C off and backed off the accelerator. When I got home, checked oil. Ended up being 3 and a half quarts low (oil light began flashing when I was pulling in my driveway). I just added 2 quarts 2 weeks ago. Not ...
3
One thing that I certainly wouldn't rule out is the SCPI Fuel Injector Assembly.
Do you know if or when this was last replaced? Getting to 216,000 on the original injector spider would make me very suspicious it (or one of the individual injectors) is the culprit. A clogged or faulty injector could also explain random misfires, and running too lean.
These ...
3
You should be able to do this with a basic set of hand tools (ratchet/socket set). I don't know what it involves to get any covers off (may require some torx sockets or drivers to remove, though is probably only connected by some 10mm bolts or fasteners). The coil itself is a "coil-on" configuration which, in and of itself, does not require any tools to ...
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