Please help troubleshoot codes

Beefcake35 · May 10, 2011

I was driving my 02 GT the other day and it started to have a pretty good miss. I took it in to have the codes scanned and this is what it came back as.

1. P0455: EVAP large leak detected
2. P0316: Crank sensor Condition
3. P0308: Cylinder 8 Misfire

Could someone help me troubleshoot this? I dont want to start replacing a bunch of parts if not necessary. Can 1 of the issues cause another?

A little more information. Its a 02 GT 4.6 with no mods other than Flowmasters. When cruising down the interstate in 5th gear if I press down on the accelerator it has a pretty noticeable chug to it. It also has a loss of power. The idle isnt too bad but even with the RPM's up there it is noticeable. There are no leaks that I can find. Plugs, injectors and coils were replaced 1000 miles ago. The car has 99000 miles on it.

Thanks in advance for your help!!

joshjwc9 · May 10, 2011

With a name like beefcake I'd be happy too.

1. Usually when the evap purge solinoid goes bad, or a large leak caused by a rotted hose going to the charcoal canister or the canister itself full from an overfill at the gas pumps.

2. Has there been any recent work done to it? IDK what could cause this..

3. Simple misfire, check to make sure the boot on the COP of the #8 cylinder isn't torn, then swap it to number 7 and see if the misfire follows the COP. If it does, it is the COP, if it doesn't the spark plug is fouled up.

trinity_gt · May 10, 2011

Beefcake35 said:
I was driving my 02 GT the other day and it started to have a pretty good miss. I took it in to have the codes scanned and this is what it came back as.

1. P0455: EVAP large leak detected
2. P0316: Crank sensor Condition
3. P0308: Cylinder 8 Misfire

Could someone help me troubleshoot this? I dont want to start replacing a bunch of parts if not necessary. Can 1 of the issues cause another?

The EVAP code could point to anything from a bad fuel tank filler grommet to a pin hole in a vacuum line under the hood. Go to your local shop and see if they have equipment to do a "smoke test" on the evap system.

P0316 actually means that a misfire was detected in the first 1000 revolutions after startup. It's probably related to P0308 (that is, the early misfire may be sourced from cylinder #8).

Try swapping the COP (coil) from cylinder 8 to, say, cylinder 5 and put the coil from 5 on 8. See if the problem follows the coil or stays with cylinder #8. If it follows the coil (i.e. P0305 shows up) then replace the COP now on #5. If it stays with #8 then pull the plug (cold engine) and inspect the electrodes. Check the plug well for oil or water contamination. If all this check out you may need to dig into things like the coil and injector wiring, the fuel injector on #8 and check the compression on that cylinder.

Plugs, injectors and coils were replaced 1000 miles ago. The car has 99000 miles on it.

Why were the injectors and coils all replaced? These are generally things that last the life of the car. Was there a driveability problem 1000 miles ago?

Beefcake35 · May 10, 2011

Thanks guys!!! You are great!

I just bought this car, so I am not sure why the injectors and coils were replaced. The seller just told me that. It ran great since I have had it... about 500 miles. I will start looking into your responses. Thanks!!!!!

Beefcake35 · May 10, 2011

I just went out and pulled the number 8 and 1 plug. 8 looks good. Slight greyish color (same as 1). the COP looks good as well. if the COP or plug were bad wouldnt it be gas or oil covered? It sure doesnt look like its misfiring to me.

Beefcake35 · May 10, 2011

Oh ya. just to verify. Cylinder 8 is the cylinder closest to the drivers seat correct?

joshjwc9 · May 10, 2011

You are correct. Take the COP from the bad number 8 to number 1 and reset the battery and see if the code comes back on, this time on number one. If the code follows it, it will tell us the COP is bad.

Beefcake35 · May 10, 2011

Ok. I will do that tonight and post what I find out. If the COP is bad though wouldnt the plug show that?

Thanks!!

trinity_gt · May 10, 2011

Beefcake35 said:
Ok. I will do that tonight and post what I find out. If the COP is bad though wouldnt the plug show that?

Thanks!!

Not if the misfire is only sporadic. Most of the time the plug is being scrubbed by good combustion. If it's only missing part of the time the plug does have a chance to be fouled too badly.

A COP that is incapable if generating sufficient firing voltage (e.g. it has an internal insulation issue, for instance) can cause problems under heavy load. It will not necessarily appear outwardly bad.

Beefcake35 · May 10, 2011

Ok I swapped the coils around and drove it about 100 miles. Still missing and chugging but the CEL light wont come back on. Should I just keep driving it and wait for the code? Is it ok to drive at this point?
Also, I noticed I can here the miss when its idling....so I pulled the wire to each coil one at a time while it was running and every one i pulled I could notice the motor change so it seems all the coils are at least doing something.

Thanks!!

screamin gt · May 10, 2011

after a problem is detected it will take a few times of it happening before the light comes back on. you can try checking it again though, since there may be a pending code even though the light isn't on yet.

screamin gt · May 10, 2011

plus as mentioned before the problem might be sporatic, so it could still be a bad coil. you probly wont be able to simulate the exact revs or situation where the problem is ocurring, so pulling them off one at a time doesnt mean much if anything.. thats why you have to use the codes to chase the bad coil. (if thats the issue) good luck

Beefcake35 · May 11, 2011

Thanks Screamin. Ill let ya know what I find. But I am sure you are right on this

evolucion311 · Aug 18, 2011

Beefcake, how did this situation turn out for you? I'm experiencing the same issue and have swapped the suspect COP and injector (cylinder 2) and replaced all plugs, boots, and the crank position sensor.

Still having the same issue you were/are.

Please let us know!

Please help troubleshoot codes

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