P0308 #8 misfire

[AMMO_HOOAH]

So I guess it's my turn for an elusive problem. I threw code P0308 a couple of weeks ago after I fixed my EGR vacuum line (it started to idle ruff and at only 600 rpm, previously 1000-1100). I reset the puter, and waited to see if it came back. Well as you can guess.... it's back.

Here's a little back ground. Plugs and wires are about two months old. I ohmed them and looked at the plug. All looks well. I ohmed the coil packs too, again checks good. So here's where I'm stumped, because Autozone lists way too many differant possible causes. Injectors, EVAP system, vaccum leak, bad cats (mine are empty), bad O2 sensor, and more. All the other possible causes are really going to be a pain, and expensive to rule out as the culprit. Any thing you guys can come up with as a way to run this down would really be appreciated. Thanks in advance for the help.

 

[Turdle]

Arcing inside the coil pack, in the secondary windings--
This would be very difficult to find with a multimeter--

A misfire code is just that--a misfire, or ignition problem.
You can rule out fuel as the culprit--

 

[Turdle]

Hey--
swap the coilpacks--
you should get a different misfire code-this will verify my suspicion--


I might be wrong though--

 

[AMMO_HOOAH]

Hey--
swap the coilpacks--
you should get a different misfire code-this will verify my suspicion--


I might be wrong though--

Sounds like a plan, the only thing that sucks is when I took them to Autozone to be checked I had to take them off the truck, so now I don't know which coil is which LOL. I guess I could reset the puter again and wait till it comes back again.

 

[Turdle]

If it still gives a #8 misfire--swap the #8 wire with another--

You have an arcing situation, I'm 99 percent sure.

 

[AMMO_HOOAH]

If it still gives a #8 misfire--swap the #8 wire with another--

You have an arcing situation, I'm 99 percent sure.

I did spritz water over all the wires at night the other day, and nothing was visibly arcing. I'll do it again just to double check. Also I still can't figure out why this started when I fixed my EGR vacuum hose.

 

[mrboyle]

If changing the coil packs around and swaping wires doesn't fix the problem I'd check to see if you somehow knocked the wireing connector on the injector, if its ok then its time for a compression test.

 

[AMMO_HOOAH]

If changing the coil packs around and swaping wires doesn't fix the problem I'd check to see if you somehow knocked the wireing connector on the injector, if its ok then its time for a compression test.

Hm, that's the second time I've heard that horrible phrase "compression test". LOL, I just don't want to think about that being the problem. I reset the puter today I'm going to wait for the CEL (takes about a week) to relight and see if it still says #8. If it doesn't bingo coil pack. If it does I'll swap the packs and reset, then plug wire, then plug. I don't want to swap more than one thing at a time to rule out the ignition side out of the cause list. After that I'll check the injector connection, and the dreaded compression test.

 

[MountaineerGreen]

Double check your wires, especially at the boot end- my wires have been giving me fits since I put my headers on. This was the source of my #8 missfire this weekend-

I have a set of Taylor 8.2mm wires on the way

 

[AMMO_HOOAH]

Double check your wires, especially at the boot end- my wires have been giving me fits since I put my headers on. This was the source of my #8 missfire this weekend-

I have a set of Taylor 8.2mm wires on the way

Dang that's pretty FUBARED. Mine "look" ok as well as ohmed out good, but I'm still going to chase it down one part at a time.

 

[MountaineerGreen]

Well, I have been chasing a problem with pour mileage lately and only recently under hard acceleration, it felt like a trans slip or something. Something didn't feel right, but I couldn't place it, but it didn't trip the CEL.

I hooked on to my camper and took off- that was the last straw for that wire. I believe it was letting the voltage bleed off a little under normal driving, not enough to trip the CEL. After I replaced the wire (always save your longest wire from your old set and carry it for a spare) it felt like it used to. Fuel mileage is right back up to where it used to be.

 

[MountaineerGreen]

I'd pull your #8 wire, twist and rotate it around and see if the jacket is cracked. If the jacket is cracked, it would OHM out OK, but still loose voltage when running.

 

[AMMO_HOOAH]

I'd pull your #8 wire, twist and rotate it around and see if the jacket is cracked. If the jacket is cracked, it would OHM out OK, but still loose voltage when running.

It looks fine externally, but the set is only a couple of months old. I'm just going to play the reset and wait game now. The strange thing is that it takes a week before it retrips, and this only started tripping after I fixed my EGR vacuum line.

 

[AMMO_HOOAH]

Well I discovered another problem that might be related I have it in another thread. I'm getting a lot of pressure through the oil breather line. Hopefully it's cheap, simple, and fixes both problems.

 

[section525]

I have a set of Taylor 8.2mm wires on the way

Source??

 

[MountaineerGreen]

Source??

Summit Racing- $99 + Shipping

I installed them least night- high quality stuff, even came with heat protectors for some of the wires.