2001 QX4 misfire, wet plug, lack of power

[ParsedOut]

Hey all, generally I'm a very competent home mechanic but this one has me a bit stumped...

Just bought vehicle with 147k miles. I previously had a 2001 Pathy and this VQ35 just doesn't feel like it has the same torque my old one does. It starts right up, it idles fine, accelerates about as well as you would expect from a VG33.

I have an intermittent P0303 cylinder 3 misfire code. I started by checking the plugs and they all looked well worn and cylinder 3 plug was "wetish". I was hard to tell what substance it was... Didn't really smell like fuel. Felt a little oily but also pretty thin. The plug wasn't particularly clean so coolant is probably out. So that leaves oil.

I also ran into an issue where a 1 hour road trip up about 4000 feet elevation caused the car to very nearly overheat. In order to keep up with traffic going up the hill she ran in 3rd gear quite a bit longer than I would have liked. As we got about 2 miles from our destination I looked down and saw the coolant temp rising from 1/2 and was able to shut it off right as it hit the H line. Pulled over and the coolant overflow was spewing out the top and was overflowing, I know for a fact before we left it was between the Min/Max lines. Let the car cool down and removed the radiator cap, idled the car and it sucked all that coolant back in and replaced the cap and have been fine ever since. Not sure if this is related but figured it was worth mentioning.

I put in a full new set of NGK plugs and swapped coilpacks on 3 and 5 to test. Fired up, drives fine, but power has not returned and the next day the P0303 came back. Crap.

So ignition is ruled out of my misfire.

That leaves fuel or mechanical issue(s). Based on the oily film on my spark plug I'm concerned I have a piston ring or valve seal issue. But here's the kicker, have driven the car a pretty hard 1000 miles and the oil level hasn't budged. No smoke out the back during driving or on a cold start.

I'm getting conflicting indicators and I'm curious if anyone can offer any insight I've overlooked?

[Towncivilian]

Change the fuel filter if it hasn't been changed within the past two years - this probably won't help with the acceleration since you have a misfire, but it is a wise idea to change it regardless.

Inspect your radiator cap according to this TSB and replace with a new OEM one if necessary.

What is the manufacturing date of your Pathfinder?

You may wish to look into checking your power valve screws and proactively applying red threadlocker to them. See this thread for more information and a pretty decent DIY guide. This issue doesn't sound like it pertains to your QX4 since there is no oil being consumed and there is no smoking, but one can never be sure.

How's the transmission fluid look?

1. Drive around for 10 minutes in the city after the transmission is at operating temperature.
2. Park on a level surface and apply the parking brake.
3. With P selected, shift through every gear and return to P.
4. Pull the transmission dipstick with the engine idling, wipe it clean, reinsert it completely, and read the level. It must be within the notched area labeled "HOT". Check for fluid contamination after wiping on a paper towel.



The fluid should be red, and not smell burnt.

Welcome to NICO.

[ParsedOut]

Fuel filter was actually next on my list, I looked under there and it looks as old as the bracket so I'm assuming it's the original.

The radiator cap looks brand new, I'm thinking this happened to the PO as well. A new one couldn't hurt though, thanks for the TSB link.

Manufacturing date is 9/00.

I'm considering taking the upper intake manifold off and inspecting the fuel injectors, while I'm in there I'll definitely do the threadlocker on the power valves.

The transmission fluid looks old. It's not that bright ATF red, but it also doesn't smell burnt either. The transmission shifts solid and can't feel any flares or slips.

What do you think about the misfire? It doesn't really sound plausible that there is enough engine oil getting in there to misfire and not be consuming oil at the same time. It's odd.

[Towncivilian]

You have 2001.5 coil packs. The ignition coil packs were revised for a "half-year" model; the 2001.0 model years had many more instances of coil pack failures. It's less common for 2001.5 packs to fail, but it's certainly a possibility.

You may want to change out all fluids and filters once you fix this misfire issue; the general info thread (link in my signature) has helpful information, I'd suggest reading through it and downloading a copy of the factory service manual, also described at the top of that thread.

I'm not sure what to think about the misfire just yet. There is an extensive diagnosis procedure described on page EC-316 of the factory service manual. I'd try to follow any of the steps which are relatively easy to work through without major disassembly just yet, then delve into the injectors as you had planned.

While you have the lower intake manifold off, I would change the PCV valve as well. Provide your VIN and I can give you exact part numbers for the gaskets and PCV valve parts you will require. It might be wise to install a PCV catch can while everything's apart to help prevent the throttle body and intake from getting coated with blow-by contaminants and oil. This thread has many pictures of the intake manifold disassembly procedure as well as an example PCV catch can set up.

[ParsedOut]

I also forgot to mention, I did a compression test on 1, 3 and 5 while I was in there. 1 and 5 were right around 155 and 3 was 210. Yeah, way higher. Not sure if this was due to the wetness in the cylinder. Now this might have been skewed because while I did remove the fuse for ignition and fuel pump I didn't let it run to burn off the remaining fuel in the lines and I don't think I pulled an injector fuse. I need to do it again under correct conditions...

[Towncivilian]

The higher compression is probably due to the wetness of the cylinder, you're correct.

Here are reference values found on EM-14:

Standard: 185 PSI
Minimum: 142 PSI
Difference limit between cylinders: 14 PSI

210 PSI is way high, that is definitely abnormal... once again I'm at a loss for an explanation, sorry!

[ParsedOut]

You have 2001.5 coil packs. The ignition coil packs were revised for a "half-year" model; the 2001.0 model years had many more instances of coil pack failures. It's less common for 2001.5 packs to fail, but it's certainly a possibility.

You may want to change out all fluids and filters once you fix this misfire issue; the general info thread (link in my signature) has helpful information, I'd suggest reading through it and downloading a copy of the factory service manual, also described at the top of that thread.

I'm not sure what to think about the misfire just yet. There is an extensive diagnosis procedure described on page EC-316 of the factory service manual. I'd try to follow any of the steps which are relatively easy to work through without major disassembly just yet, then delve into the injectors as you had planned.

While you have the lower intake manifold off, I would change the PCV valve as well. Provide your VIN and I can give you exact part numbers for the gaskets and PCV valve parts you will require. It might be wise to install a PCV catch can while everything's apart to help prevent the throttle body and intake from getting coated with blow-by contaminants and oil. This thread has many pictures of the intake manifold disassembly procedure as well as an example PCV catch can set up.

Fluids are definitely on my list of to-do's but are a bit down on the priority list.

I'll do the fuel filter, redo the compression test using proper procedure and inspect the fuel injectors. If that still doesn't yield results I'll do a leak down test and cross my fingers it isn't anything serious. Not sure where to go from there.

[zach7685]

Keep me posted i have the same issues

[zach7685]

ParsedOut, Does the pathy feel like its towing a semi when accelerating from a stop? Could you smoke the tires? does it build power after the initial acceleration? Do you have access to another pathfinder to compare it to? Because mine feels like the 3.3 engine compared to my other one.

[ParsedOut]

I wouldn't say "towing a semi" but it doesn't have the grunty torque I was used to in my other VQ Pathy. Haven't tried to smoke the tires... haven't tried to do that in any car I've owned in the last 10 years. I'd suggest you start with the big 3. Spark, Fuel, Compression. One of those is lacking.

[zach7685]

Iv done that I don't have a compression tester yet and I meant do you feel the car has enough torque to break lose.

[ParsedOut]

Doubt it.

[ParsedOut]

So I just had a thought... The "wetness" (oil?) on the spark plug is getting there from one of four places. Piston rings, valve seals, headgasket or valve cover gasket. Based on the mileage, none of these could be considered unlikely. The fact that the oil level is not dropping, that tells me that it's a small leak. I've noticed that the SES light usually comes on when the car starts up and not after driving for a while. This tells me a small amount of oil is making it's way into the cylinder at rest but not continuing to burn while driving. This puts the piston rings and headgasket down the list as they would continue to leak. Leaves valve seals or the valve cover gasket. When I pulled the spark plug I did notice some oil all the way up the threads and not just on the tip, this tells me that the oil "might" be coming from the top and slowly leaking down the threads and into the cylinder. Valve cover gasket is looking to be more and more likely.

This weekend I'm doing the fuel filter and another compression test, while I'm in there I'll do my best to take a real good look down the spark plug cavity for signs of oil leakage. Fingers crossed, that's all it is. Wish me good thoughts.

Oh and Towncivilian, I appreciate your assistance up to this point. Just realized I didn't say thank you.

[Towncivilian]

You're welcome

You can tighten the valve cover bolts before going straight for replacement, sometimes they back out somewhat and can cause leaks.

[Chuck Tribolet]

The valve cover gasket isn't going to cause a wet spark plug electrode.

Chuck

[ParsedOut]

I suppose you're probably right. If the plug were fairly loose and the inner valve cover gasket "ring" were leaking it could most definitely get into the combustion chamber with enough volume to wet the electrode. I realize there are a lot of ifs in that statement... But now that I think about it, the coilpack end would have oil residue on it and I'm pretty certain it was clean. Ehh... valve guide seals are looking more and more likely.

[Chuck Tribolet]

If the plug were that loose, and the valve cover gasket was leaking:

A: you would have said "WHAT!!" when you broke the plug loose and found it already loose, and,
B: you would have an oily mess in the engine compartment.

Bad valve stem seals will manifest as a smoke cloud on start up, but not thereafter. My
'87 Corvette has that problem, which is well known in early C4 'vettes. I don't worry about
it much because once I fire it up, I drive 800 miles to Tucson to see my mom.

I hope it's valve stem seals because that's the easiest to fix.

Chuck

[ParsedOut]

My old Astro minivan (don't ask...) used to smoke at start up for the same reason. I'm not getting any visible smoke at start up though. It's got be just enough to leak down the spark plug and make it misfire shortly after start up but not enough to produce visible smoke? Uhg... At least I know that is something I could fix but really really don't want to have to.

[zach7685]

don't know anything about wet plugs but I know that the coil pack I replaced was lose and slightly off center. Fixed that and I got like 6000000 HP back.

[ParsedOut]

Well, the verdict is in... I'm getting coolant in the combustion chamber while the car sits.

Pulled the plugs again and sure enough, cylinder 3 top of the piston was wet and noticed a small puddle at the bottom. Rocked the car back and forth and that puddle sloshed around in there, yeah that's bad... Stuck a white zip tie down there to dip in the puddle to check the type of fluid. Sure enough it came out with a slight pinkish tone and tasted like coolant (yeah I licked it, haha).

So I have a bad headgasket, which also makes sense with the overheating incident I had where the coolant system got all steamed up (or so I thought at the time) and displaced the coolant and caused the temps to rise. While I was going up the hill my coolant system was slowly being pumped in with combustion air until it vapor locked.

Now I need to figure out how to do a headgasket or how much it'll cost to have it done.

[zach7685]

Do you not have the green coolant?

[ParsedOut]

Nope, red/orange/pink whatever... not green.

[Towncivilian]

That would probably be DexClone "all makes all models" coolant, which is not optimal for our cooling system.

Have you checked the power valve screws? It's still possible that one or more came loose and caused damage.

Sorry that you've got a head gasket issue, it's definitely not a common occurrence with Pathfinders in my experience. I hope the costs aren't too awful.

[Chuck Tribolet]

If you replace the pink coolant with green, make very very sure you get all the pink out before putting the green in.
Do multiple flushes with fresh water, a final flush with distilled water, then 50:50 green:distilled water.

Chuck

[zach7685]

l

[ParsedOut]

Coolant type is kind of low down the list of concerns that this point.

I will take care of it when/if I get the mechanical issues resolved along with all the other deferred maintenance.

Well it makes me feel better to know that headgasket issues aren't common on the VQ35DE, actually no it doesn't...

[Chuck Tribolet]

Mixing coolant types is a bad thing. When DexCool first came out there were stories of the coolant turning to jelly when the
two types were mixed.

Chuck

[ParsedOut]

Thanks Chuck. I'm aware of the issues of mixing the orange and green. Right now the coolant isn't jelly and is a pretty red/orange color. When the headgasket issue is resolved, I am doing a full fluid flush from front to back.

[Towncivilian]

I would use the new blue Nissan coolant for the flush, if possible. It is compatible with the original green fill.

Good luck with the head gasket.