Question about Saturn SL1
I have a 2000 Buick LaSabre that suddenly started not running well. The Service Engine Soon light often starts blinking, and stays steadily on at other times. I went to AutoZone and they read the trouble codes that say that the system is detecting "random cylinder misfires".
The thing is that just a month or two ago I was having similar engine trouble, though the diagnostic then was stating that a specific cylinder was misfiring. I changed all the spark-plugs, since my mileage is over 100,000. However all the old plugs looked really good. Unfortunately, the problem persisted, so I changed the wires. Then the problem was solved. (I did find that the coil connector side of the wire for the diagnosed misfiring cylinder was charred. So I'm sure that was the real problem. Though I have concern over what damage may have been inflicted upon the coil and/or the Ignition Control Module.)
So I know that my spark-plugs are new, and so are my wires. What would help me in further diagnosing this issue would be to know how the system determines misfires, and whether it would report a "random" cylinder misfire if a pair of cylinders were misfiring---specifically if the pair of cylinders driven by a single coil (of the three on this vehicle) were misfiring?
Does the system determine such misfires through a detection of the ignition impulse sent to the spark-plug (back EMF, current, etc.), or does it have some ignition sensor within the cylinder (detecting light, heat, sound, whatever)? The answer to this question will help direct my diagnosis.
If the system does not have the ability to identify a pair of misfiring cylinders, but will provide the "random" misfire code even for a pair of misfiring cylinders driven by the same ignition coil, then I could rightly suspect a coil. Otherwise, I don't suspect a coil since this would require multiple coils to be acting up. (Not impossible, but not so likely.)
The thing is that the sound of the engine doesn't suggest "random" misfires. It sounds quite regular, even though the gas mileage I'm getting suggests I'm running on only four of my six cylinders.
David 1999 Saturn SL1
Code P0300 Random Cylinder Misfires, also shows a code related to cam position sensor.
Car was running very smoothly, then parked it for 1-2 months. Upon startup it ran VERY rough. Changed plugs, no improvement. Plan to change ignition wires.
Any other suggestions??
The cam sensor code is the part to concentrate on, also check the timing belt for excess play causing the camshaft to whip, this will cause a random miss.
Posted on Oct 30, 2008
Get a Haynes manual for your vehicle and use the troubleshooting guide there. about $20 from amazon, auto parts store or haynes.com. This WILL save you time and shortcut this and any future diagnosis. Haynes IMHO are top notch and I like them better than some factory service manuals that fgo for $100 and more.
David, 99 Saturn, Cam position sensor codes seem to indicate a engine timing (not spark, but crankshaft/camshaft sync). Old timing belts or worn tensioners can cause belts to jump a tooth or two which can have a pretty dramatic effect. The belt could also be old/dryrot and have lost a tooth or two causing it to jump. If any of these are the case, or if the timing belt interval is near, replace timing belt, tensioner, idler roller if present and water pump. FYI, quality OEM ignition wires shold last at least 10 years. If they are really bad, you can open the engine compartment on a dark night and you will see sparks arcing between them and/or something metal nearby. We all replace wires when we are not sure what the problem is, and regardless of what anyone tells you, it only rarely solves anything unless the car is more than 10 years old.
Posted on Oct 30, 2008
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Posted on Jan 02, 2017
SOURCE: Random Cylinder Misfire
Im having the same problem with a 96 buick century. I wondering if its the coil packs. The plugs and wires have 8000miles of use. So i think it shouldnt be them. But same symptoms, engine code P0300.
Posted on Aug 12, 2008
SOURCE: Random Cylinder Misfire
The problem is the ignition control module such is under the coil packs. It seems to be an internal problem in the design. I have seen it many times and if you don't belive as many will not. So disconnect the modules electrical connector and just let it sit for two to three days. After that clean ir replace your sparkplugs, they will be fails up dew to it running lean and rich. Plug it in. Plug it in and wala its fixed $ but only for a week or two then back to the same thing so in short change the ignition module and save time and money, and don't forget to thank your friendly neighbor hood mexican mechanic.
Posted on Sep 10, 2011
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