P0305, P0300 - Cyl 5 misfire and random cyl misfire

[yoface13]

up front, yes, i've searched and i've one a bunch of stuff based on what i've read... i just want to make sure i'm doing everything right and maybe this will help someone else...

givens: d2, 120k, new plugs (ngk plats i think) and new magnecore 7.5mm wires about 20k ago along with a head gasket job. i use lucas oil stuff in the gas at least every other tank. and i've been doing that for probably about a year.

i've been getting P0305 and P0300, cylinder 5 misfire and random misfire. going with easiest first, i figure i'll go with the plugs, even though they're probably okay. i think they were autolite platinum's i put in. anyways, the old ones didn't look terrible. the worst one was #3. they were all about .23mm off of the d2 recommended gap. well, that didn't help. i still got the codes. i also looked for arcing with a spray bottle but found none at the plugs or the coil pack.

next step, sea foam. people like doing that. i didn't think i'd have a problem with the injectors as i use the lucas oil stuff in my tank pretty often. the intake procedure seemed interesting though. anyways, put half a can in the intake and the other half in the gas tank. cleaned throttle body - which looked pretty good already - i am one of those guys who either have an awesomely sweet and clean intake or i did it wrong, because i didn't get the smoke that everyone talks about. i got a little bit, but nothing to brag about. started driving. 10 minutes in, got the codes. and the codes continued.

today, when i got home, i left the disco on, and used the throttle body cleaner to find a vacuum leak. i sprayed it all over. i thought i hit the jackpot when i sprayed it on the iacv hose connected behind the valve because i got a good rev (~100 rpm's). well, it's been about 5 hours and the kids are asleep and i go back out to see if i can get it to rev again. well, no luck this time. maybe since the air valve thing hadn't even been opened in 5 hours, maybe the computer was expecting weird crap coming through the iacv? i don't know. but, it did seem like i could get the p0305 to light up when i sprayed in that area.

i have a coil pack and intake gasket coming in soon, so i guess that's probably the next thing i can do. i'm going to clean the maf sensor, and i know these things go bad easily, but i just replaced it about 4 years ago.

the image is of the hose i thought was letting a leak in just in case you were wondering. and for anyone that's screwed around in there lately, is the red connecter (lower right hand corner) supposed to have a little back and forth play?

any ideas? i certainly appreciate this board.

 

[yoface13]

alright. i just tested the old coil pack through the wires. i had continuity. is there a general range of resistance that i should be getting between plug wires 5 and 8? 7.5mm magnecores and the stock coil pack read out at about 24 kΩ. since i am getting continuity, would this indicate that the coil pack is fine?

 

[jymmiejamz]

I'd start with putting some new coils on it if the wires are good. I'd also install new wires while you have the coils out, even if they've been replaced.

 

[yoface13]

makes sense. thank you! i'll keep this updated until i get it fixed. any quick suggestions on the wires? while researching this issue, i've seen that magnecores have lost their allure.

 

[Keanan]

Try this, move the plug to cylinder 1, swap the wire with the one from cylinder 4.
Clear the codes then drive it around.

Misfire cyl 1= plug
Misfire cyl 3= coil
Misfire cyl 4= wire

 

[lugnut]

24k resistance is close to right. after cooling off and restarted later does it run rough for the first few sec.? 3,5 and 4,6 for cylinder liner leaks are the 4 worst cylinders to go out. Have seen few valve issues in the past. skips under load? or light normal driving? compression test will give some better insight. the connector for the booster vac. the play is normal but should not have a vac leak.

 

[yoface13]

hold on, what does a misfire on cyl 3 have to do with it? you mean, if it's completely random and not on cyl 1 or 4 (or 5)?

 

[yoface13]

i don't think it runs rough for the first few seconds. it's pretty normal, unless my version of normal is rough. and i've had the code thrown a pretty much all times. under light load, after load, no load. haven't really noticed a correlation with heavy load. i doublechecked the connector for a vac leak and i didn't find one.

i'll switch my wires around and if it isn't that, i'll change the coil pack. maybe i can get the truck in tomorrow for the compression test and maybe a smoke test to find a leak. (still haven't been able to find a leak with another can of starting fluid.)

 

[Keanan]

hold on, what does a misfire on cyl 3 have to do with it? you mean, if it's completely random and not on cyl 1 or 4 (or 5)?

Sorry I was thinking Cyl 3 instead of Cyl 5.


This is what i should have said:

Try this, move the plug to cylinder 3, swap the wire with the one from cylinder 6.
Clear the codes then drive it around.

Misfire cyl 3= plug
Misfire cyl 5= coil
Misfire cyl 6= wire


What this does is isolate the misfire. You are moving the plug and wire to different locations to see if the misfire stays on Cyl 5 or moves. If it moves you found the cause, it's the plug or the wire.
If the misfire stays on Cyl 5 it could be the coil, injector or another problem inside the cylinder.

Don't worry about the random misfire. Fix the cyl 5 misfire first. Most likely the random misfire code will go away once the cyl 5 misfire is fixed.


A vacuum leak could cause a misfire, but I don't think it is your problem. What are your long term fuel trims?

 

[yoface13]

hm... posted a reply last night, but it looks like the internets failed me... again.

cool, that makes sense. i was just wondering if you were making a reference to the wasted spark system.

check this out. swapped the wires last night and took the truck for a spin. no codes. we'll see how it does in the middle of the day.

i checked that all the plugs were seated in the coil pack; although, i did not unseat and reseat.

bank 1 = -3.1%
bank 2 = -2.3%

tad rich. good right? i probably use lucas fuel treatment too often, but it says on the bottle that it's real safe.

 

[yoface13]

i'm working on switching the coil pack right now. i just got the inlet manifold off and check this out. #3 looks terrible. or is that terrible? well, it looks worse than all the others. i actually thought they'd be cleaner than this. but check out #5. spit-shiny clean. in the immortal words of double rainbow guy, "what does this mean?" #5 needs to look terrible not #3.

 

[yoface13]

okay, hopefully the last post on this one. what i called #3 in the previous post was actually #4. but the issue is still relevant, or not. i thought #5 would be filthy or something. not some other one. but, maybe the recent misfires haven't really attributed to any fouling. then how dirty they were would mean nothing.

so, i just swapped out the coil (thank you will t) and i've been code-less for 30 mins. what i've established so far...

1. just because you have continuity between the paired plugs, even if the resistance is similar to the other ones, doesn't mean that your coil pack is healthy.
2. there's no such thing as magnacor 7.5mm's. i tricked everyone; they're 8.0mm's.
3. don't trust harbor freight torque wrenches. i ruined a few non-essential bolts. maybe you can't use extensions with torque wrenches, because if you get the seat angle off, it screws with the actual torque applied and does not allow the wrench to properly "click" when the targeted torque is applied.

and for anyone who cares, the old coil pack (wires off) read around 14kΩ between the paired contacts. the new one - which was actually used - read almost 13kΩ between paired contacts. based on my earlier measurement, the resistance of the #5 and #8 magnecor (8.0mm wires have a conductor 2.0mm in dia) wires and the 4 terminals is about 10kΩ. which stacks as they list the resistance of these wires 9.8kΩ per meter which would be the approximate length of #5 and #8 added together.

thanks to all who helped. and thanks to everyone that's posted about these misfiring issues in other threads.

 

[yoface13]

Ok. This morning I got p0305 back. What's next. The compression test?

 

[psykokid]

Try swapping injectors on the suspect cylinder. You may also try unplugging and cleaning the injector plug contacts with electrical contact cleaner and re-seating all the injector plugs.

 

[jymmiejamz]

You probably have a cracked block.

 

[singingcamel]

That's just what I was thinking while reading this thread.
Pull the heads and have a peek , may be a worn cam lobe on # 5 , pull the lifter and look for wear .

 

[nolift911]

MAF - replace. I have found to keep the truck code/trouble free, you get about two+ years out of these things, cleaning does not much good after that time.

 

[yoface13]

hmm... weird, i didn't see all of the replies come through in my email. the internets must have hacked my internets.

anyways. holy crap. that doesn't sound good. a buddy that's way better than me at everything looked for a vac leak. couldn't find one. he's thinking injectors as well. i'm not getting smoke or anything in the exhaust, so he wasn't thinking there was a huge issue block issue. i'll clean and swap the injectors to see if that helps.

then i'll check for a cracked block. here's the thing... man i don't want it to be that.

 

[pinkytoe69]

If its cracked, you can run some block sealer through it and buy yourself some time.

http://landroverforums.com/forum/discovery-ii-18/adventures-irontite-cracked-block-58715/?highlight=irontite

 

[yoface13]

Swapped injector plugs and resetting the whole bank. Forgot to clean with electric contact cleaner. Got p0305 again. I'm going to try to get to a compression/ leak Down test this weekend. I have another can of sea foam on hand. I'm going to try to saturate intake #5 just in case it's just a sticky valve after all this time.