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Unread 06-20-2011, 08:38 AM   #1
ChrisHager
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Question P0305

Hello all!

So I took a trip to St. Louis this weekend and on the way there, noticed my vehicle was kind of surging a little on the interstate. It continually got worse. At first, I thought it was the transmission. I turned off overdrive and it was not so bad, for a bit. It then became horrible - surging, misfiring, etc. and the CEL started flashing. Ironically, it started the worse part right on the bridge coming into STL where traffic was crawling! Anyways, I was able to limp into town and into a parking garage near my hotel.

Pulled the codes and found P0305 - Misfire on cyl #5.

This code didn't come on until it was a clear misfire. When it was surging earlier, no codes.....

Another strangeness is that if I start the Jeep, it will sometimes run fine, other times misfire.

Anyways - 04 GC 4.0L

Clearly, I need to replace the spark plugs first since they probably are the originals at 87k. Champion seems to be the general consensus. Any other good plugs you all like?

I was advised to replace the boots and springs while I am in there. Thoughts? I can get BWD boots w/ springs for about $5 a piece.

Does the ignition coil pack go bad often? Does this behavior seem like a bad ignition coil? Is there a way to test the coil to see if it's bad? If I need a new one, any preferred brand:
Master Pro - $175
BWD - $105
ACDelco - $?

I know GC's are particular on their brands and types of parts. Sorry if I'm blasting too many questions at everyone. I just figure if I NEED to be replacing parts, I might as well do it once, do it right...

Thanks in advance.

Chris

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Unread 06-20-2011, 08:44 AM   #2
WiCkeDuDe
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Change the plugs first. No reason to change the coil at this point. Champions are best for the 4.0.
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Unread 06-20-2011, 09:15 AM   #3
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the 4.0 has a coil rail not sure you can replace anyting on it, I think it is a one piece replacement and gets all six cylinders at once.
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Unread 06-20-2011, 10:08 AM   #4
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Yeah that is correct - 1 rail, everything connected.
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Unread 06-20-2011, 02:21 PM   #5
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Could be injector. You may want to swap two to see if the misfire moves cylinders.
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Unread 06-20-2011, 07:37 PM   #6
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Wj

I had a similar problem with my 04 when the vehicle wiring harness came loose and landed on the engine block. Had to replace a burnt wire and fuel injector...
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Unread 06-20-2011, 08:27 PM   #7
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Thanks for the tips so far. Here is what I have done:
Replaced the spark plugs. I put the champion plugs in. The previous owner must have changed the plugs once before because they had autolite's in it. When I did this, I disconnected the battery as well, clearing the codes. Took it for a test drive and after it got warmed up, it started in again. That may be a hint - to what I'm not sure - it seems to be worse when it's warm. Sometimes it seems to run fine, just a little sluggish. Other times it misses horribly.

OK so then I dumped in some Chevron Techron fuel injector cleaner (I know, some people will say this is a good idea, others will say it's a waste of time and money). Anyways, I did this thinking maybe an injector was clogged. Took it for another ride out in the country, stop and goes, high speed stretches, to run some of that through. No luck.

So then I decided to swap out injectors. Man is it easy to get to the injectors! I was pleasantly surprised. Anyways, I wiped off some gunk that was on them (the actual nozzle was shiny clean) and swapped 4 and 5. Not that it will affect this current problem, but I went ahead and cleaned the throttle body while I had direct access to it. It didn't look too bad but was due for a cleaning. Put it back together, still no luck.

So here is where I am: Tomorrow I'm going to change out the coil strip thing (yeah, yeah, quite technical description). Small question - My girlfriend's dad has an 00 TJ Sahara 4.0L. He had switched his coil out thinking his was bad a while back. That wasn't his problem. So he has the 'old' coil that he says is still good. Will this one work or should I get a new one? I looked on oreilly's website and it looks like both vehicles has the same part number for the BWD coil. Also, should I get new boots/springs? The boots looked good but I noticed at least one spring wasn't 'perfect'. It had a slight bend in it.

If this doesn't work, any suggestions towards my next step?

Thanks in advance,

Chris
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Unread 06-20-2011, 08:34 PM   #8
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Quote:
Originally Posted by ChrisHager View Post
Thanks for the tips so far. Here is what I have done:
Replaced the spark plugs. I put the champion plugs in. The previous owner must have changed the plugs once before because they had autolite's in it. When I did this, I disconnected the battery as well, clearing the codes. Took it for a test drive and after it got warmed up, it started in again. That may be a hint - to what I'm not sure - it seems to be worse when it's warm. Sometimes it seems to run fine, just a little sluggish. Other times it misses horribly.

OK so then I dumped in some Chevron Techron fuel injector cleaner (I know, some people will say this is a good idea, others will say it's a waste of time and money). Anyways, I did this thinking maybe an injector was clogged. Took it for another ride out in the country, stop and goes, high speed stretches, to run some of that through. No luck.

So then I decided to swap out injectors. Man is it easy to get to the injectors! I was pleasantly surprised. Anyways, I wiped off some gunk that was on them (the actual nozzle was shiny clean) and swapped 4 and 5. Not that it will affect this current problem, but I went ahead and cleaned the throttle body while I had direct access to it. It didn't look too bad but was due for a cleaning. Put it back together, still no luck.

So here is where I am: Tomorrow I'm going to change out the coil strip thing (yeah, yeah, quite technical description). Small question - My girlfriend's dad has an 00 TJ Sahara 4.0L. He had switched his coil out thinking his was bad a while back. That wasn't his problem. So he has the 'old' coil that he says is still good. Will this one work or should I get a new one? I looked on oreilly's website and it looks like both vehicles has the same part number for the BWD coil. Also, should I get new boots/springs? The boots looked good but I noticed at least one spring wasn't 'perfect'. It had a slight bend in it.

If this doesn't work, any suggestions towards my next step?

Thanks in advance,

Chris
if you have a known good coil rail give it a try. As I said you can not replace boots and springs, they are made into the coil rail and are replaced as one unit.

as mentioned check the wiring at the back of the coil rail where it plugs in.
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Wife's ride, pretty stock
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Unread 06-20-2011, 08:40 PM   #9
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Oh I'm sorry I miss read your earlier post! I understand what you're sayin now. I'll give the TJ coil a shot tomorrow evening and check for wiring issues. I'll post back results. Thanks again!

Chris
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Your symptoms sounds just like what it does when it's not doing what it should because of how it is.
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Unread 06-21-2011, 05:47 AM   #10
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Quote:
Originally Posted by ChrisHager View Post
OK so then I dumped in some Chevron Techron fuel injector cleaner (I know, some people will say this is a good idea, others will say it's a waste of time and money). Anyways, I did this thinking maybe an injector was clogged. Took it for another ride out in the country, stop and goes, high speed stretches, to run some of that through. No luck.
Tried the same thing when I had P0308, and that did not help with my injector woes on cylinder # 8. P0308 kept coming back after the Techron. Replacing injector # 8 was the only thing that actually cleared the P0308 for me.

Quote:
Originally Posted by ChrisHager View Post
So then I decided to swap out injectors. Man is it easy to get to the injectors! I was pleasantly surprised. Anyways, I wiped off some gunk that was on them (the actual nozzle was shiny clean) and swapped 4 and 5. Put it back together, still no luck.
When you say "still no luck" do you mean that it is still running poorly? Because if you have a bad injector in cylinder # 5, then the bad injector will just end up being bad in cylinder # 4 when you move it. If you were getting P0305 before and now P0304, then you have found your problem. You need a new injector. You cannot tell whether an injector is good or bad by just looking at the nozzle. You need to see the spray pattern, and you cannot really do that. It could be gunked up inside.

However, if you moved the #5 injector to #4, and you are still getting P0305, then you pretty much know that the injectors are fine. That would lead you in the direction of electrical (plug, coil, and wire) or something actually wrong with the motor (rings, head gasket, etc.). Could also be even fuel pressure / pump related. A weak pump with individual injectors that are partially gunked up could enough to get a misfire on one cylinder. Normally, you would get P0300 with a weak pump.
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Unread 06-21-2011, 07:13 AM   #11
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Originally Posted by kentman View Post
When you say "still no luck" do you mean that it is still running poorly? ........ However, if you moved the #5 injector to #4, and you are still getting P0305, then you pretty much know that the injectors are fine.
Yeah I definitely was not clear on that. When I swapped injector #5 with injector #4, it still ran poorly. I drove it 'around the block' and got the CEL to flash more. When I got back to the house, I pulled the codes and still only received P0305.
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Unread 06-21-2011, 05:29 PM   #12
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Another Update...

I changed out the ignition coil and am still missing on cylinder #5...

BUT...

There is a pronounced chatter under the valve cover. Clearly something is going on under there. Originally, I heard some sort of noise (maybe a ticking) but assumed it was the missing going on. Since it's more pronounced now, we are thinking (and hoping) that something has worked loose.

As soon as I eat and the engine cools off, I'm heading back outside to do a compression test (for baseline numbers) and removing the valve cover to see what's going on under there.

Feel free to throw ideas out. I'll post back results here in a bit hopefully.

Chris
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Unread 06-21-2011, 08:39 PM   #13
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Originally Posted by ChrisHager View Post
Since it's more pronounced now, we are thinking (and hoping) that something has worked loose.
Sounds ominous to me. I am not sure that you are going to like what you find.

Detonation kills. If you had a cylinder head run into a compression detonation wave due to lean condition in # 5, then you could have bent a rod.

Any knocking noises from the motor in advance of the P0305?

There is something obviously wrong with the mechanicals in that cylinder. Hopefully, it is not rod / piston related. If it is valve or lifter related, then you may be able to swap out some parts and get running again. Let's hope nothing is too damaged. I would not want to bet a paycheck that the motor is an easy fix at this stage.
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Unread 06-21-2011, 09:27 PM   #14
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Well you're pretty close. The lifter on one of the valves for cyl 5 - not positive which one - must be flattened? malfunctioning? ... it's not working. haha

SOOOOOO..... the head get's to come off. I'll state the obvious first - I checked the torque on the rocker to make sure it didn't work loose. Unfortunately, that is not the case. And since this issue became progressively worse, I'd say there's not a quick fix.

Not sure when I'm going to tackle this project as I didn't really foresee removing the head after 6 months of owning it...with only 86K on the clock.

Either way, I hope to take pictures and document my work so someone else can benefit from my experience.

Anyone have any ideas why this would happen? To answer your question kentman, i did not notice any knocking or ticking before this started to happen. I was cruising down the interstate around 70-75 with two passengers, not towing, when it started to SLIGHTLY miss. Within about 20 minutes, it went from a slight miss to a full on rough running engine. And since then, my test drives have made the lifter tick go from nil to horribly obvious.

Chime in with any comments or tips! It'd be great to do this soon. The only reason I may wait a bit is I just bought a new house with a 2.5 car garage (that will be air conditioned!). I close on it in a month. So if I can wait a month or so, I'll have that to work in. If I decide to do it now, it'll be in the yard and direct sunlight . I am also fortunate enough to have my girlfriend's 00 Wrangler to drive around until I get this fixed so at least I don't have to walk to work!

As always, thanks for the help and suggestions so far!

Chris
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Unread 06-22-2011, 06:09 AM   #15
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That is the one downside of buying used. You really have no idea on the history of the vehicle. It is credible that the previous owner had some foreshadowing of this issue and decided to dump it before the problem got out of control. They may have treated the motor poorly.

Issues do just happen from time to time on a motor, and it may be completely independent from the previous owner experience. If you noticed nothing for six months, then I would give the previous owner the benefit of the doubt. It could just be a poorly manufactured part or a stack up of tolerances. Defects happen, and sometimes those defects take time to show up. It could have been poorly torqued at the manufacturer. Another scenario could be that the previous owner had something like a blown head gasket, and the people repairing it before sale did a poor job on reassembly. Who knows.

I like the sound of air conditioning in the garage. I was in our garage last night working on our convertible, and the humidity was unbearable. I gave up after about an hour or so. I would put in a large window unit, but I would be run out of town by our home owners association (HOA) if I tried. They do not even let me work on my car in the driveway. It has to be in the garage. With the windows open in the garage and with the three car bay doors wide open, it is not that much different from just being on the driveway. Everyone can still see me. I really hate the HOA Nazis.
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