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Davo
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Category: Car
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Experience:  ASE Master Technician/Advanced Automotive Diagnostic Technician
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1999 Olds Intrigue: 3.5 liter, auto trans..light came

Customer Question

1999 Olds Intrigue, 3.5 liter, auto trans. "Service Engine Soon" light came on. Flashes when accelerator is depressed, steady when coasting or braking. Engine shakes pretty hard when idling and somewhat noticable at low rpms. problem came out of no where, WHAT HAPPENED???
Submitted: 11 years ago.
Category: Car
Expert:  DCM replied 11 years ago.
The best you can do is have the system scanned and get the code stored on the OBD (on board diagnosys) if you don't have the equipment have it done @ any auto shop. Once the system is been scaned the given code will point you exactly where is the problem, with out the code there is no way we can tell.
Customer: replied 11 years ago.
Reply to DCM's Post: I will have it scanned first chance. I'll reply again then.
Expert:  Davo replied 11 years ago.
Autozone will scan for the codes for free son that will save you a couple dollars.If the service engine soon light flashes it means you have a catalytic convertor damaging misfire.Thats the only time it will flash.Getting the code will narrow down the cylinder/cylinders affected then comes the figuring out what is causing it.I'm enclosing a picture of one part to check,look closely at #3 its located under the covers(coil cassette) on the front and rear of the engine.Look for any type of burn marks gray or black usually.You may have to remove the dipstick tube to remove the front one.These are where the coils and modules are located also.The plugs are underneath them.If this helps please click on my accept button.If you feel it has helped you very much you may add a bonus if you wish. Object Number: 256308  Size: SH
Expert:  Davo replied 11 years ago.
Object Number: 256329  Size: SH
Expert:  Davo replied 11 years ago.
These 2 pics show the coil cassette location oObject Number: 256304  Size: SHn the engine.
Customer: replied 11 years ago.
Had computer scanned, the code is "P0303". I'm thinking of checking the spark plug, which one is #3 (I'm sure it's in the rear, just my luck). I have pulled off the cover and see the 3 in front.
Expert:  DCM replied 11 years ago.
the number three is the one in the middle @ the back your are right, just follow Davo/diablo666 direction above and you wond be lost.
Customer: replied 11 years ago.
got them all out, back middle, #3 is dark / oily??, not like the rest. The rest have a whitish / greyish look to them, almost an ash, which should be correct.
Expert:  Davo replied 11 years ago.
Either the #3 plug is bad or the boot in the picture is bad or you have a bad module or coil.I would replace the plug first and go from there.If there are any black sooty lines on the porcelin part of the plug or the top where the insulator boot goes make sure you replace the insulator and the plug at the same time or you will have a repeat failure.You will be able to feel if the misfire is gone if it is you can go back to Autozone and have the light turned off by clearing the code.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: Here is what I have done so far. I changed all 6 plugs, No improvement. Switched the plug wires, no improvement. Swapped coil packs, no improvement. Still shows Cylinder 3 misfire.
Expert:  Davo replied 11 years ago.
What I would do next is either swap the modules front to rear or the entire coil cassette assembly front to rear and see if the misfire follows the module.If the misfire follows the module you need a new module.If the misfire doesn't follow the module you may have a mechanical problem and would need to do a compression test to confirm it.Make sure you clear the codes and recheck for the misfiring cylinder after each swap you do.The #3 misfire code will be there for quite a while unless its cleared with a code reader or scan tool.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: Tried swapping coils already, cleared the code, then received P0303 again.
Expert:  Davo replied 11 years ago.
Did you take the rear assembly and swap it with the front?Not just the coils the complete coil cassette assembly.There are 2 ignition modules on your car one in front and one in the back and they are in that coil assembly.Its very important to be clear on this.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: Yes, swapped entire assemblies, still shows the cylinder 3 code. The code was cleared between tries to.
Expert:  Davo replied 11 years ago.
You are going to have to do a compression test.Autozone can rent you the tool I would think.One other thing to check is to pull the fuel injector pressure regulator hose off and see if gas is coming out of it when the engine is running.You can try this before the compression test.You may also have a fuel injector problem which could be isolated by swapping them between cylinders.In fact although some added work is needed it may be your best option.If that doesn't lead you to the problem you may have to get a noid light to check #3 injector for pulse.You may want to also leave the fuel lines connected to the fuel rail and turn the key on with the injectors unplugged.If any fuel comes out of any injector the injector is bad.Do the injector testing first since you don't need to spend money on that.

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