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I have used TitanTalk as a resource since I bought my 2006 Titan LE (4Wd) new. It has 98,000 miles, is out of warranty, has never been wrecked or had any major repairs (but has had all scheduled maintenance), and recently suffered a major setback. Its only modification is a leveling kit that makes room for 33" M/T's. it has mostly highway miles (I still have half life in the original brake pads at 98K). Starting two months ago, my beloved truck started having a serious problem: the engine would aruptly stop. This usually happened at idle, but it also happened at highway speeds. I took it to the dealership and met an advisor we will call Mr. Liar. After two days for the truck Mr. Liar said it needs new catalytic converters (all 4), a new transfer case, a new fuel pump, and a new engine. He claimed the oil was full of metal particles. He told me that the fuel pump was failing, causing a lean condition, causing the intake and exhaust valves to be open at the same time, and causing the catalyst to disintegrate. He claimed that that the catylitic converters were sucked into the engine. I paid the diagnostic fee and walked. He actually mocked me for driving away, saying it would be back in two days on a tow truck. To provie him wrong, I left it sitting in the driveway for THREE days before I started looking at it. Other than dying unexpectedly and then being hard to start, it was running fine. I had really taken it to find out why the SES light was on and expecting to get a new fuel pump. I changed the oil (no metal shavings at all); changed it again (same story), and filled up the transfer case.

A few days later I was driving it and it went into limp home mode. It was in BAD shape. THe truck is paid off, so I got on ebay and staarted looking for a replacement vehicle.

Having nothing to lose, I dropped the exhaust and found that the driver-side primary cat was EMPTY. However, it appears that the first cat's catalyst just blocked the second cat on that side, since when I put a shop vac over the back of the second cat it barely pulled any air. Again, having nothing to lose, I gutted all of the cats and the truck started working really great. Mission success. I stopped bidding on cars and started reading up on headers/cats/exhaust systems on TitanTalk.

I also took the truck to autozone for a free OBDII reading, and, of course, there are emissions problems. Oddly, theirs also showed a random misfire--the dealership never mentioned that. I was advised to get new spark plugs and, if that didn't work, new coils.

Yesterday, I got all new fluids and replaced the spark plugs with new NGK plugs. I forgot to check the gap. The truck is running worse than before limp home mode because there is some sort of miss going on; this wasn't a problem before. Essentially, the miss is a non-issue unless the truck is idling under load (transmission engaged) or driving at low RPMs (like about 1500), during which there is a clear miss. From the engine compartment everything sounds great but underneath and at the tailpipe I can hear a miss that is pretty regular. I checked each coil and they all have springs, good wires, and good connections. They are all making a sparks. I reset the ECU (several times, using both the battery and on/off/accelerator pedal methods) and the IPDM (I also switched the relays), following advice found on TitanTalk. Nothing seems to make a difference. I did notice that the air filter housing was only closed on one side (from the last oil change at the dealership) and lioned it back up. Again, no difference.

I do not have good automotive repair skills, and I have now stopped short of buying new coils and headers/cats/etc. becase this problem was not present ten minutes before I replaced the spark plugs and I want to tackle one issue at a time. Of course it is entirely possible that I screwed up one of the coils since I have never changed spark plugs before (and had never even seen a coil), but they all seem toi be in contact, intact, and in good shape.

I am suddenly deeply distrusatful of the dealership. I live in the woods so no one here works on foreign trucks. I am so far ahead of the game now (and have an extra car) that I can take my time with the remaining issues. TitanTalk is such a great resource, I am hoping someone else might have a suggestion. I have even considering putting the old spark plugs back in to see whether the miss goes away.

Does anyone have a suggestion or has dealt with the rough idle/miss issue before? I have read everything I can find on the issue and am beginning to get a little overloaded with breadth of suggested fixes: Mass Air Sensor, IPDM, ECU, coils, exhaust leaks (I obviously have that, but I had it before the spark plug change), dirty throttle body (had that before the spark plug change, too, I guess), etc. Can someone steer me in the right direction?

At the auto parts store the clerk told me that gaps were set for my truck at the factory; now I am doubting that. Could that be the issue? Any help would be greatly appreciated.
 

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Yesterday, I got all new fluids and replaced the spark plugs with new NGK plugs. I forgot to check the gap.
There's your problem. Your spark plugs don't have the proper gap.
 

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The service manual on my 2004 specs gap at 1.1 mm = 0.043 in

Another thought is that one or both of the breather hoses may have become disconnected during your spark plug install. I think these feed into the intake downstream of the MAF and could result in a rough idle if they are sucking excess air resulting in a lean mix. I noticed that these hoses easily slip off when I was installing an intake.
 

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Discussion Starter #4
The service manual on my 2004 specs gap at 1.1 mm = 0.043 in

Another thought is that one or both of the breather hoses may have become disconnected during your spark plug install. I think these feed into the intake downstream of the MAF and could result in a rough idle if they are sucking excess air resulting in a lean mix. I noticed that these hoses easily slip off when I was installing an intake.
Wow, I feel dumb, or lazy, or both. The first plug I pulled was crunched and had a gap of 0.0. I put an old plug in its place and the engine ran as smooth as ever. My SES ligt even went out, which is amazing with no cats. (I forgot to mention that one of the OBDII codes was for the A/F sensor, but that could be explained by the random misfire and subsequent mushed spark plug. The exhaust no longer smells like gas... just smog). I am sure that won't last. Time for a quick inspection.

So, thank you gentlemen!

If I still have your attention, let me ask a couple of other questions. The gross vacuum leak is DEFINITELY the little hose at the back of the gas tank that runs to the filler cap atop the filler tube. It is totally off. It doesn't look replaceable (looks like it is welded/glued to the tank at the fitting). Is there any reason I can't jusr JB Weld the hose--very carefully, of course. I can reach it without taking the tank off.

As i said, I am getting ready for an inspection. In my part of the world it will pass without cats and in its current condition, but I need to replace them anyway, and that requires new headers, too. Might as well get an exhaust, since I am saving the $15,000 that Mr. Liar said I needed to pay. Do you have any suggestions about that? I find stock setups online and I am confident I can install them by myself, but I also see long tube headers with no front cats that promise more horsepower and fuel efficiency. I really don't understand the need for four cats anyway, as long as the SES isn't burning a spot on my retina.

Thanks again,

Charles
 

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I believe your 2006 4wd has primary cats in the exhaust manifolds and secondary cats in the B-pipes. I have a 2004 4wd with the same arrangement. I installed Doug Thorley long tube headers (with no cats in the headers although they do have sensor bungs), custom made B-pipes with Magnaflow 94035 cats, and JBA cat-back exhaust. I also installed an Injen intake and flashed the ECU with UPREV. Forum member Von made the B-pipes and shipped them to me and they bolted up. I am advised that he is no longer doing this, but you might send him a PM to make sure. The advantage of that is you can DIY install with no welding. There are four o2 sensors: one in each header and one in the aft end of each cat. The one complication was extending the cable for the rear driver side O2 sensor about a foot. It runs over the cat heat shield so I used PTFE insulated wire and wrapped the cable in a velcro secured heat shield. This works fine but might be avoided by flipping the driver side cat so that the sensor is oriented down and to the inside instead of up and to the outside. I have no SES codes and others have posted that this will pass sniffer emissions. The 94035 cats are larger than the OEM cats and sized to handle the engine size and GVWR of the truck. So I don't think you need four cats and the 94035s were only $58 each.

On the gas tank, people have had EVAP cannister leaks throwing codes.

http://www.titantalk.com/forums/titan-general-discussion/85852-evap-vent-control-valve-replacement.html

EVAP Vent Control Install Filter Kit - 2004-2006 Titan :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com
 

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Just a note on the spark plug gaps. The Iridium and I think the Platinum Plugs too, have very fragile tis and truly are preset at the spark plug factory. That is why they have a strong cardboard tube to protect the delicate tips. Normal gapping tools may break them. My NGK Iridiums said to not touch them.
 

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The Iridium and I think the Platinum Plugs too, have very fragile tis and truly are preset at the spark plug factory. That is why they have a strong cardboard tube to protect the delicate tips. Normal gapping tools may break them. My NGK Iridiums said to not touch them.
Yeah, they may say that. I just installed a set of NGKs in my civic and the gap was not correct from the factory. The gap was WAY smaller than the OEM spec even though they were the proper plugs for my car, so I delicately gapped them with feeler guages and all was well. I understand that they are delicate, but you can't just install them with the wrong gap. IMO you should always check the gap regardless of whether they are "pre-gapped" at the factory.
 

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Discussion Starter #8
Just a note on the spark plug gaps. The Iridium and I think the Platinum Plugs too, have very fragile tis and truly are preset at the spark plug factory. That is why they have a strong cardboard tube to protect the delicate tips. Normal gapping tools may break them. My NGK Iridiums said to not touch them.
I didn't get that warning and I did drop one plug during the install--probably that one. But I can tell you I was going to gap that one (the mushed one) with the gap tool just to drive and buy another and I couldn't get it to budge without putting a lot of force on it. They are not expensive enough to chance losing it in the engine so I tossed it. I'm going to get a new plug today.
 

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I believe your 2006 4wd has primary cats in the exhaust manifolds and secondary cats in the B-pipes. I have a 2004 4wd with the same arrangement. I installed Doug Thorley long tube headers (with no cats in the headers although they do have sensor bungs), custom made B-pipes with Magnaflow 94035 cats, and JBA cat-back exhaust. I also installed an Injen intake and flashed the ECU with UPREV. Forum member Von made the B-pipes and shipped them to me and they bolted up. I am advised that he is no longer doing this, but you might send him a PM to make sure. The advantage of that is you can DIY install with no welding. There are four o2 sensors: one in each header and one in the aft end of each cat. The one complication was extending the cable for the rear driver side O2 sensor about a foot. It runs over the cat heat shield so I used PTFE insulated wire and wrapped the cable in a velcro secured heat shield. This works fine but might be avoided by flipping the driver side cat so that the sensor is oriented down and to the inside instead of up and to the outside. I have no SES codes and others have posted that this will pass sniffer emissions. The 94035 cats are larger than the OEM cats and sized to handle the engine size and GVWR of the truck. So I don't think you need four cats and the 94035s were only $58 each.

On the gas tank, people have had EVAP cannister leaks throwing codes.

http://www.titantalk.com/forums/titan-general-discussion/85852-evap-vent-control-valve-replacement.html

EVAP Vent Control Install Filter Kit - 2004-2006 Titan :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com
Great suggestions! I have always wanted to learn to weld but this might now be the time or project to start, so I will do as you suggest. I got a little lost on what happens with the front O2 sensor with your setup.

What does your system sound like? Did you get a HP/econ bump from that setup? And just for curiosity's sake, why did you change from the stock setup?
 

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Yeah, they may say that. I just installed a set of NGKs in my civic and the gap was not correct from the factory. The gap was WAY smaller than the OEM spec even though they were the proper plugs for my car, so I delicately gapped them with feeler guages and all was well. I understand that they are delicate, but you can't just install them with the wrong gap. IMO you should always check the gap regardless of whether they are "pre-gapped" at the factory.
I also check the gaps - if they're off I just return them. I read somewhere (take it fwiw) that the coatings crack when iridium plugs are gapped.

Also - on a different vehicle I had no cats for several emission inspections - passed just fine. As long as you're not throwing a code (mine gave up on trying to tell me after about 2 weeks) the inspector has no idea.
 

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(1) I got a little lost on what happens with the front O2 sensor with your setup.

(2) What does your system sound like?

(3) Did you get a HP/econ bump from that setup?

(4) And just for curiosity's sake, why did you change from the stock setup?
(1) The front 02 sensors go into the sensor bung holes provided in the headers. No modification required.

(2) It is louder than stock, mostly when accelerating, although I think JBA is regarded as one of the quieter performance exhausts. It sounds good.

Exhaust sound clip thread:

http://www.titantalk.com/forums/titan-performance-modifications/29965-exhaust-systems-sound-clips-list.html

Not my truck, but this will give you the general idea:

http://www.youtube.com/watch?v=jdtpYQmCNG4


(3) Definitely +HP +torque and +1 MPG even though I have not driven conservatively. UPREV also removes the WOT from standing start limitation, so the acceleration improvement is very apparent. I also have a TruTrac limited slip installed, otherwise you can expect to be spinning one rear tire if you mash it from zero.

I have never had it on a dyno, but typical stock numbers are 275 hp / 330 ft-lbs and after intake, headers, exhaust, UPREV - maybe something on the order of +25 hp and +30 ft-lbs for dyno tuned UPREV based on post 19 in this thread:

http://www.titantalk.com/forums/titan-performance-modifications/99644-best-programmer-2.html

The guys that race and pay attention to the dyno tuning numbers may have better input here.

(4) I had a cracked exhaust manifold and headers actually cost less than buying new OEM manifolds.
 

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I also check the gaps - if they're off I just return them. I read somewhere (take it fwiw) that the coatings crack when iridium plugs are gapped....
That's true. The Iridium is brittle and can crack, the same goes for platinum. Platinum and Iridium plugs are supposed to be pre-gapped but sometimes they're a little off. I've heard several people say along with reading a couple posts on the forums, that they damaged their plugs while trying to gap them. The problems with that is it's not always obvious until after you install them and start the engine, and then the store usually will not take them back.

It's usally best to return them asap for new ones. If it were me, I'd check the gap in the store before buying them if I found some that were off.
 

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Sparkplugs.com - Spark Plug 411
Check out "Gapping" subject in our FAQ. You can gap iridium and platinum plugs, but as has been stated, be very careful of that center electrode.

Another thing worth mentioning is if you need to change the gap more than .008" either way think about obtaining a different sparkplug with the correct gap as the center and ground electrode will no longer align properly and can produce a weak spark.
 
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