So I had this code come up. Symptoms prior to check engine light:

Hesitation under acceleration
Gurgling sound under acceleration
Rattle near passenger side floor
Dirty exhaust

The code said coil pack was bad or suspect

Changed out the coil pack and the symptoms above completely went away. Today light came back and noticed maybe twice a misfire on the #6 cylinder again. I didn't change out the spark plug and I'm thinking that may be the issue. I questioned changing one plug. Should I change them all at the same time?

Car was upgraded to LS6 block, bored, kooks headers and exhaust, MSG plug wires, think the existing coil packs are Dalton? This was all done less than 20k miles ago.

 

Fouled plug, running like a champ again. Will inspect the remaining plugs.

 

Light is back

 

Foul plug again?

 

Brand new iridium plug, so I would think not, haven't pulled it to check. What controls the coil packs?

 

The ecm . See what code you are getting and switch that coil to another cylinder and see if it follows .

 

Doesn't follow, have swapped wires as well to next door plug. Problem is getting worse.

Took a pic of the intake



I'll get pics of the other spark plugs coming out of the #6 cylinder.

Changed the oil tonight.

 

Gonna just change all the plugs

 

Change all the plugs today to Iridium Autolites. Seemed to run fine at first start and idled for about 5 minutes listening. Had to shutdown and restart, had a zero oil pressure indication. Re-started and oil pressure climbed to normal. Sensor going bad maybe? Anyways first test run and hesitation and misfire for coil pack #6 cylinder are back. Check the plug for ignition on the #6 cylinder and its firing.

I suspected maybe the fuel injectors, discovered I have Ford XL3V-A5A 42lb injectors, surprised to see Ford parts. The car is tuned.

Disconnected the battery for the night, read somewhere about computer resetting any compensation.

Inspecting the injectors and cleaning them. Will move the #6 injector next door and vice versa. I also removed the intake and doing a good cleaning on it, cleaned out the intake ports best I could. Mostly just oil buildup near the entrance.

Am I going overboard here on all this or does anyone have any explanation for the rough, sputtering, and misfire?

Also the Oil Pressure Sensor was extremely oily maybe why I had a zero oil pressure indication?

The small vacuum line was already disconnected as well. I had suspected that it was as I could hear a vacuum leak prior.

 

What code are you getting just the p0356 ? Did you switch the coil and inspect the harness ? If you had a bad injector you would get a p0206 code . Is there a p0300 for random misfire ?

 

Yes, just the P0356. Service manuals say that the code will set on the second consecutive misfire, but light doesn't come on immediately despite multiple noticeable misfires. I usually have to drive for a bit before it will come on, or drive for about a mile, shutdown, then restart and light will be there. I've been clearing the codes each time. I have also replaced the coil pack with a new one, and have put the old one on other cylinders but light stays on the #6 (P0356) despite the troubleshooting.

I removed the intake to clean it up because I'm going to install a catch can and hopefully eliminate the messy oil buildup that was in mine. Plus the throttle body was really dirty.

I've google'd the hell of out this issue and I can't seem to find an explanation why it's happening or at least a general idea of what it could be.

 

Oh and yes inspected the harness, I don't see any cracked wires. However I guess I might have to shoot wires. I use to work F-15's so shouldn't be too hard, found the schematics online. The popular chaffing point near the drivers side rear intake area appeared great and no chaffing evident.

 

If you have a timing light you can start hooking to spark plug wires and ensure they're firing correctly.

Infrared heat gun the primaries to ensure all the injectors are working... I'm kinda at a loss on this one as well.

 

I had a pinched wire to my coil pack and started fouling out the entire bank. It was running ok but just not right. Voltage had dropped to 11.2 from the bent wire, plugs were all kind of black. I replaced coil packs, plugs, and the pigtail.... All good now.

Just food for thought

 

After everything I have done, I am almost sold there is a short to ground in the harness. The good news is the oil pressure sensor I think is or is going to crap out, picked that up today since I have the intake off. Its a geyser of oil. Also the vacuum line will get reconnected and hopefully I get back my HVAC vent switching. Going to pull the HVAC control as it has fallen to the lights out issues. Going to install the LEDs.

I will post later on results from the wire harness inspection. I really wish I had a military aircraft wire harness braider, I'd pull the whole harness inspect/replace suspect wiring and then braid it tightly together. But I'm out now and not anywhere close to an F-15 base.

 

Ok so here is what happened tonight. Took the intake over to the car wash, rinse only I washed off all the oily residue that had been soaking for a day in cleaner. Stuck it in the oven on warm to make sure all the water was out, evaporated, etc. Actually didn't take long. 170 degrees, left the door ajar.

#1 - Last night I dropped an injector on linoleum. Cracked the pintle cap, cursed, then retrieved replacement kit from NAPA today.

#2 - Oil pressure sensor behind the intake, dirty POS, cleaned with contact cleaner, after about 5 mins, oil residue oozing from base of plastic female connector. Replaced it!

#3 Replaced intake manifold gasket, and installed foam pads that were not replaced previously, missing.

#4 Cleaned the hell out of the throttle body with SeaFoam, build up grim melted away with that stuff. Probably should have worn gloves for that part. It has some nasty stuff in it, specifically MEK, Methel Ethel Ketone, that will clean anything! And will most likely kill you over time from repeated exposure.

#5 Excessively cleaned intake filter, its green, looks like a K&N but I don't think it is. Cleaned up very nicely though.

#6 All plugs were replaced with Iridium Autolites

#7 Checked for ground on the #6 cylinder injector wires. Results were sketchy, bought a Wal-Mart special, highest priced multi-meter, out of the box, intermittent open tester wires. Really, brand new, bad leads. This step abandoned.

#8 Installed clean intake, connected rear items, torqued. Vacuum line connected. What a PITA that was!!!

#9 Reconnected battery that was disconnected for the last 24hrs.

#10 Test Drive

AMAZING!!! Its not mis-firing. What in the hell out of all that fixed it? Also I have switchable HVAC from defrost to vents!!! I mean this car idled smooth, very responsive throttle, however test drive cut short as mother nature decided that today was a good day to snow, and tomorrow my day off, and then 60 on Monday. Anyways hope this thread helps someone out. I'm thinking there still might be a bad wire in that harness and it was just re-connected from having to loosen and move the harness out of the way for the intake removal.

 

Just my 2 cents, but I would have left the foam pads off. It's one of the first things I do with a new car I get. Rip the pads and dam the KS with RTV.

Even the TSB GM put out said to leave the rear pad off, so the condensation can evaporate and escape.

Anyway, glad you have it all sorted out.

 

Light came back, got a decent multimeter to begin troubleshooting further. Upon first glance, which I should of noticed sooner, there was an old inline splice on the coil pack connector, letter F wire. Took off the splice and there was one wire strand left. Repaired the wire temporarily, problem is now fixed! I will have to rewire this summer. Has anyone beefed up the wiring gauge? Wires seem pretty flimsy and prone to breakage. Really wish I had access to some F-15 bench stock to make a new wire harness that would never wear out.

 

Part of the fix was the vacuum line. I am assuming you mean the small, straw sized line at the back of the intake manifold which provides vacuum to the HVAC system. Fixing this makes mixture control possible and restores some of the HVAC valve actuators.

 

The "straw" just wasn't connected. Re-connected it and I can switch from Defrost to vents now. Before nothing happened, just always defrost.