Mechanics

I NEED HELP WITH A MISS-FIRE ISSUE...

2002 Saturn SL1 • 85 miles

Hello all,

I have a 2002 Saturn SL1 with 85k miles on it. Today I had to take it into the shop because the engine light came on. I was told the Error codes are as follows:
po300, po340, po341 and po442. Now I did some digging and was told to replace the ICM and coils. I did that and it still miss-fires.A lot more actually. I tried new plugs and still the same problem. Now i'd like to get it fixed by myself. Should replacing the Crank Position Sensor resolve my issues? With the po442 code would I be correct in saying I need a new EGR valve?

Thanks,

Martin
Avatar
Liquidarts
July 8, 2012.




Fault codes never say to replace parts. That's where a lot of people get "wrapped around the axle". While a sensor or other part is usually the cause of a code, they really just mean that's the circuit or system that needs further diagnosis.

A bad crank sensor will prevent the engine from starting.

Besides a bad EGR valve, you could have insufficient flow from a plugged passage, a carbon particle holding the valve open at idle, or a bad sensor.

Caradiodoc
Jul 8, 2012.
Thanks for the fast reply. I forgot to mention the miss-fires happen not at idle but while driving. It usually occurs around 2300-2500 RPM's.

I kinda figured it wouldn't be the Crank sensor like you said as it wouldn't start.

Tiny
Liquidarts
Jul 8, 2012.
If it's hard to feel at those higher speeds and you only know about the misfire because of the codes, I think I'd be looking closer at the injectors. With a single cylinder misfire you can switch two injectors to see if the code moves to a different cylinder. Random misfires are harder to narrow down.

Code 442 is not related to the EGR system. That refers to a small leak in the vapor recovery system. You can try tightening the gas cap but more likely there's a leak in a hose. You almost always need a smoke machine to find those. They allow you to inject a white non-toxic smoke into the system, then you look for where it's sneaking out. Cracked hoses and loose clamps are common causes of that code.

Caradiodoc
Jul 8, 2012.
I found out to take it to a friends shop to re-read the codes as the engine light started flashing when I was in 3rd gear at 2300RPMs n found out about the random miss-fires.

Yeah i've tried tightening the gas cap n nothing.
AD

Tiny
Liquidarts
Jul 8, 2012.
When the Check Engine light is flashing, that means too much raw fuel is entering the engine and damage to the catalytic converter can result. The Engine Computer has lost control over fuel metering or it is responding to some erroneous sensor information and commanding too much fuel. You need a scanner that can display live data to tell the difference. The fuel trim numbers will be high positive if the computer is requesting more fuel. The numbers will be high negative if the computer knows too much fuel is going in but it can't control it.

Caradiodoc
Jul 8, 2012.
Oh wow...thanks alot for your expertise. Not sure if I can post links but was wondering if this walk-through for the po340 & po341 would work to solve it.

http://www.saturnfans.com/forums/showthread.php?p=489512

Tiny
Liquidarts
Jul 8, 2012.
Sounds like this fellow solves all misfires with that chart. It's definitely worth a shot to give it a try. If I had to throw a dart to come up with a solution, I'd throw it at the spark plugs and wires. Since you did the plugs already, try misting the wires with water while the engine is running. If you see arcing, replace them. If you don't see arcing, that's not conclusive. The insulation could be fine but the carbon string inside could be burned away from a terminal.

Caradiodoc
Jul 8, 2012.
Many thanks Caradiodoc. Will give it a shot.

Tiny
Liquidarts
Jul 8, 2012.
Just to add to this one who ever said to replace ignition module and coils for the P0340 code is crazy.99 percent of the time on that car replacing the plugs and wires will fix that code. It does sound like bad wires though like cardiodoc suggested. Also what type of plugs did you put in the engine?I dont recomend platnuim in that car.

Saturntech9
Jul 8, 2012.
I replaced the plugs with Autolite 3926 with a.040 gap.

Tiny
Liquidarts
Jul 8, 2012.

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