"Service Engine Soon" Light

What are some of the causes of this light to come on? I've replaced the plugs and the wires and it's still on.

I have a 1996 Firebird 3.8L V6.

I'm sure there are a whole host of reasons, but what are some of the major ones?

it could be so many things it is unreal! but to take a shot it could be coolant level, oil presure and level, o2 sensor, catylitic converter going out, fuel pressure drop, air filter going bad, battery voltage drop or spike, mas airflow, idle air control valve, throttle position sensor, water temp sensor, transmission sensors, crank position sensor, coil packs getting weak. give us a little more detail on how it is acting and what you were doing when it came on and we can narrow the list a bit better or make it longer if need be

Take your car to autozone if you have one around or were ever they scan cars and have them scan it for free. To start guessing at parts is insane. Good Luck


John

I took it to my mechanic and it said "Cylinder #4 misfiring" They had replaced one of the coil packs for me, but now the other two seem to be pretty close to going out as well. It looks like something I could do myself. It only looks like unhooking a few wires and a few bolts. Does anyone have experience replacing these coils? and is it fairly simple? or should I not bother...

its easy and fast to do but usually when the coils start going out as soon as they do the ignition module follows soon after.The only advice i have is be careful installing them not to damage the connections to the ignition module,and if the module(under the coils) looks burnt or cracked change it too,if your wallet can handle it.

I have a 96 3.8 L as well. I replaced all of the coils and the module. It was easy.... like a 20 min swap. It didn't take care of the problems... many dollars later it was the fuel pump, hope urs is only the coils...

Is there a way to ground the diagnostic connector out with a paper clip to retrieve the trouble codes from the ECM like in the older model F-Bodies?

Not on 94 and 95 F-bodys and not on 99 percent of OBD2 systems.

John

I get that light a LOT!!! :lol:

Good luck finding the problem. Coils should be fairly easy to replace.

Im currently working on a 2002 olds alero and according to the diagnostic it has a misfiring cylinder number 3.So i purchased new plug insulator boots wich are equal to plug wires,new plugs,and tried a new coil and ignition module set off a coworkers brand new cavalier,wich had the same exact motor.

With a brand new module and coil set,the problem was uncured.Turns out that even the codes said nothing about it, and fuel injector number three has stopped functioning properly.I found this out by unplugging each injector and noting the change.When i unplugged number three,the idle actually went up.When i unplugged numbers 1,2 and 4,the car almost died.

So now im at the point of installing a new injector for cylinder number three.But according to the diagnostic system,the problem is in the ignition system,since the check engine light is flashing,and the codes read by auto zone said number three had a misfire.The injector still has electric pulse,but obviously is clogged or somthing.

the lesson we must learn is to check each system and dont always believe what the diagnostic says.
Im lucky a coworker had a brand new car with the same coil and ignition module system to run a test on the car with the problem,or i probably would have bought 300 dollars worth of crap for the car and not one dollar would have been closer to finding the problem.

Not on 94 and 95 F-bodys and not on 99 percent of OBD2 systems.

John

I had originally thought that, but I had a friend of mine tell me that I could ground out the diagnostic connector to get the codes. Thanks.

there is a way to get the codes out using an analog needle type meter you can usually find the instructions on how to do this and a basic code list in your chiltons or haynes manual. you need to remember that 90% of these code scanner such as the one auto zone uses (actron) is no very indepth and not greatly accurate and even those we use in dealerships such as the s.t.a.r. program for dodge and the ford f.a.c.t. programs are not all that great either. the only one that i have found that give you a good description is the snap-on solus scanner. This thing costs around 6000 and gets updated every so often. just remember when you get the code desciption you need to make a list of probable causes. just because it says misfire it is not just the ignition system involved it is just telling you that the cylinder stated is not firing. it could have a hole in the piston or stuck valve these would cause it to misfire just the same as no spark. problem solving saves time and money.

I get that light a LOT!!! :lol:

Good luck finding the problem. Coils should be fairly easy to replace.
Except your light doesn't say check engine(although if I had yours I would be checking it every ten minutes) it says check yourself.:loser:

your right custom machanix the one we have up at the shop agreed with autozones diagnostic(wich auto zone has a pretty nice diagnostic system here in oklahoma).ours at the shop have little cartridges you plug into it and they update those and the connectors for the data stream all the time for newer and different models.But two different diagnostic systems said it was the same thing,and they both lied through their lcd's about it.A 2002 and here i am back to the primitive unplug and plug in stuff routine,wich served better diagnostic than anything else

no hole in the piston tho the compression on this motor was strangely exact,at 155-160 all the way across

Except your light doesn't say check engine(although if I had yours I would be checking it every ten minutes) it says check yourself.:loser:
Pretty much, yeah. :icon16:

I get P0300 a lot. Lopey idle tends to do that.

you see what i thought if the original wiring.Oh and the exhaust...No more check engine light hahaha!
http://files.automotiveforums.com/gallery/watermark.php?file=/500/260330wiring_harness-med.jpg

What am I looking at? Is this one of those things that if you stair at it long enough it makes sense?

Thats the wiring harness that goes from the computer inside,out through the passenger fender to the motor.What you looking at is a wiring connector that went from inside to the outside of the car.It had about fourty wires going to it now its just a useless lump inside my fender well.

Oh and those familiar with the gen threes will notice it has no exhaust where all of them did wich in the picture would be any place you can see the ground.

I have purchased two ignition coils and will install them this weekend. I hope it works, but from the sound of some of these posts, I probably shouldn't be optimistic.

It should run better but i dont know if it will help the check engine light or not.

my mechanic has offered to reset the code on the service engine light for me if I did the work myself. of course, it's irrelevant it the coils aren't the problem.

back to square one then, I suppose.

worst part is my inspection was due in january and i can't get it done until this issue is resolved.

I was able to replace the remaining two ignition coils myself. Didn't take care of the problem. I can't wait to see what they can find next! THis is a nice Pandora's Box. And a black hole for my money.

My 96 3.8 had the same problems. I can almost gurantee it is the fuel pump. It is what it was on mine and i know a few other cases. A fuel pump issues won't create a code in our year (that was added on later) The code is being set by the misfires. Sometimes it is the fuel pump relay tho. It's about $20 or so and it's an easy install... once u find the relay (which after much searching is under the driver's side door panel by the hood release). The relay didn't help me... it was the fuel pump. Honestly, I would get the fuel pump checked out. They can tell you if it's working properly before you go and spend the $ on this.

thanks. i will definetely check that. the service engine light is actually off for the moment. but it's still running very rough.