Like the title says, I'm becoming increasingly sensitive to the car running rough when the engine is cold, and having it smooth out as soon as it gets up to running temperature. With the phenolic spacers, I swear it gets to running temp real quick, so this "problem" really isn't a big deal... particularly with winter over now.

But it's still bugging me. Things like MAF, O2 sensors, Knock Sensor... those would all throw SES codes, and I'm clean. And like I said: it's only when the engine is cold.

Is it possible to have a leak that seals itself at temperature?

Mods are in my sig. Advice is certainly welcome.

It is possible there is a vacuum leak that goes away after the spacers expand from the heat. Also, sometimes knock sensor problems don't always throw a code, but I don't know if that would make your engine idle rough.

Try taking the spacers off and re sealing them with some black RTV.

Did this start after installing the spacers, and has it been getting progressively worse? If it started after the spacers, it is possible that you have a tiny vacuum leak that seals up when it gets up to temp, but not really likely.

Your car should run rich and a little rough from cold idle until it gets up to temp normally, but it wouldn't be especially bad.

What kind of rough is it? Is it misfiring/stumbling or does it just sound rough?

Hi, guys. Thanks for the posts.

Spacers were installed in September of 2009, so that makes 6+ months with the spacers. In November, two months later, I had a BG Products intake/engine cleaning service. Immediately thereafter, I had the Throttle Body replaced; (on BG's dime, which was rather nice customer service.)

It's really been just in the last month or two that I've been sensing the car running rough when cold. It's definitely not missing on any cylinders, I know what comes from having a coil pack go bad. And just 2 weeks ago (after new struts, brakes and other stuff) my mechanic checked for leaks on the spacers, and was liking what he saw. However, I hadn't mentioned this problem to him at the time. (We had a big list, and I wasn't sure yet what I was feeling yet about the whole running rough thing.)

When I say "rough", I mean there's more vibration, kind of a bumpy feel. And the engine sounds more like a sick growl than a deep-toned purr. That last observation is kind of dumb, but there it is anyway.

It's also possible that I'm becoming overly sensitized to every little thing as I become more obsessive about the car. And in the last 12 months, (since I've been participating in this forum), a whole lot of mods have been leading me down the crazy road.

What RPM does it idle at when cold and running rough?

I know that when my engine is cold, it idles around 1200RPM until it warms up.

It is very hard to feel any vibrations at 1200RPM, but after warm up, the idle drops to ~600, and I feel some minor misfires. I have ES motor mount inserts, do you?

When stone cold, it runs 1200-1400, and will drop to 1000 at a dead stop, clutch in.

When at temp, it runs 900-1100, and will drop to 700 at a dead stop, clutch in.

i.e., normal idle.

I know it's a little off the wall, but cCould the rough feel be coming from the front suspension? Worn strut cushions maybe?

Also, what other "stuff" did you have done?

EDIT: Nevermind about the struts. I just read your post again and you said it goes away after it warms up.

Guess I'll put on my thinking cap now...

The sense of it running rough while warming up was with me before 2 weeks ago.

However, here's what was done on March 24; (cut-n-paste from another thread):

• Tokico HP Blue Struts
• Moog Front Strut Mounts
• Moog Front Sway Bar End-Links
• Energy Suspension FSB frame bushings
• Centric Rotors
• Hawk HPS Brake Pads
• Front Airbag Impact Sensor
• Lower Coolant System connector pipe
• Front Valve Cover and Gasket (2004)

Nothing on that list would cause the issue you are having. Let me check into it.

Maybe the spacers are leaking? It's possible that they are leaking and sealing themselves. But..nah... that would cause a lean code. I don't know dude. I will keep at it.

EDIT: What kind of plugs do you have and how old are they?

NGK Iridium Tips. Approximately 2 years old, give or take 6 months. 15,000 to 20,000 miles on them.

#3 plug was swimming in oil for a little while, when my rear valve cover was leaking 6 months ago. It was cleaned up, looked OK, and a new valve cover & gasket were installed; (same time as the Spacers.)

Along this same line of thought... 2 of the coil packs are new in the last 15,000 miles. The other 4 are all original; (58,000 miles on the car). All of the fuel injectors are original.

Would a failing IAT thermistor demonstrate these symptoms? Or does the IAT simply work or not work, with no in-between? I'm inclined to not think IAT because that's air temp on the intake, not engine temp.

On the plus side, it's like 80F today, and the engine got to temp so fast as to almost not notice how it was running when "cold". In other words, I'll likely not obsess too much over this during the upcoming summer, unless it gets worse.

My 2.4 Camry and my DSM both sound a bit "rough" when cold, but when they warm up it subsides.

I think a lot of it has to do with the properties of the oil and overall properties of metal expansion. When oil is cold it's thicker and once it's warmed up it becomes thinner, or less viscous, therefore allowing it to lubricate and flow better. Hence why some cars with HLA's get lifter tick when the car is cold but once the oil pressure becomes consistent and the oil becomes less viscous it goes away. Also something to think about is, the parts in your car (Even though it's a very small amount) do expand and contract as your engine warms up and cools down. Once your car is warmed up everything seals and sits a bit tighter than it did when it was cold.

Overall if you take care of your car (Which it sounds like you do) I don't believe you have anything to worry about. As you own a car and become familiar with it you start to notice more things about it. Hope this helped!

It speaks to a possibility that I've suggested, which is that I'm becoming hyper sensitive to normal operation as I become more obsessive about the car.

I must say, you're making an awesome first impression, LingLing. It's nice (and rare) to read posts that demonstrate good language skills. Looking forward to reading more from you on the Forum.

I figure since I'm thinking about picking up a 5th gen for a new DD, searching around on Google and on here only reinforces and adds to what little knowledge I have of Nissan's. If it ends up helping a fellow car enthusiast it just ends up being a win/win.

Just out of curiosity, what type/weight of oil are using?

A well-cared for 5.5 gen has great intrinsic value for the cost. Good choice.

Penzoil 5W30. The dealership does it. Lifetime oil-changes every 3,000 miles.

How would you guys check for an IM leak? I'm reading about using carb cleaner, with claims that if you're spraying over the leak it will temporarily close and cause the rough idle to go normal for a few seconds. I was kind of hoping for some visual cue.

That's the easiest way to go. If for some reason you have a UV reactive smoke machine you could go about it that way, but the easiest way to do it at home is the way you mentioned. Just do small sections at a time, that way it won't make isolating the problem area a pain.

Water out of a spray bottle works too.

i have the same problem ends up being the intake manifold gasket there crappy from the nissan

Note the mods in my sig, and the discussion throughout... I don't have an intake manifold gasket. Spacers + RTV.

If I can find the time, I'm planning on experimenting this weekend with some carb cleaner around the intake.

I've also heard that the Iridiums can run a little rough at first and smooth out after a while. I wonder how it would run with just Platinums.

Thanks for thinking outside the box, Roy.

I was considering swapping out my plugs this Summer, which would probably be the last set for the remainder of my ownership on the car. And this time around, I'm planning on going back to the NGK plugs that are OEM. The Iridium Tipped NGK's... I think that's more marketing than real value. They certainly weren't what the engine was designed for.

Although, if I do actually have an IM leak, the plug swap will be happening immediately, to coincide with that work.

I had a very similar problem, when cold, car had issues holding idle. It would shut off until car was warmed up. I took intake manifold out and cleaned it. Inside there was some kind of butterfly looking thing. I cant remember whats it called.(gas saver, fake vtch idk). It seems that 90 percent of maxiez with the plastic manifold has that specific part broken in it. I removed that part i enjoy the ****ty gas mileage and i kinda feel a lil more power idk. Ever since i never had an issue with it...

^^^
I wouldn't call that a similar problem. Your car didn't hold idle and actually shut down. My issues aren't even remotely that severe. That, and you have a 5.0 gen with the plastic IM.

I'm thinking I have a very, very small leak somewhere that is only an issue when the car is cold. But that's just a guess. I haven't actually experimented with looking for it yet.

lol, im kinda slow dis mornin, just realized u have an 03.

Rochester, for what it's worth, I put Iridiums on my Max when I put my headers on about two months ago. I've had something similar going on since. I've noticed my car will run sort of rough and crunchy when it's cold, but once the car gets warm, it purrs like a kitten. It's more noticeable with my headers now that there aren't heat shields and big, cast-iron manifolds to block out the engine noises.

I have the original manifold gaskets. Mine were in good shape, so I just re-used them, and double checked to make sure everything was torqued to spec when I was done, so I don't think that I have a leak anywhere.

This makes me wonder if maybe the Iridiums actually aren't as great for our car as they claim. Maybe Roy's onto something.

Guys, I did not test for an intake leak this past weekend. Way too many chores, and I was coming down with a cold, (that I still have, dammit. )

Anyway, the reason I'm bumping this topic is that in the last few days this problem has mostly gone away. With each day now, that sense of the car running rough when cold is getting less and less.

So, either the problem was a small leak that has been sealed (huh?), or the increasing temps with the season are providing a positive impact on the problem... or it's all in my head and I'm dealing with it there.

You know, maybe all three.

You sure you weren't just tripping from the NyQuil?

I certainly can't rule that out. My senses aren't firing on all cylinders lately.

It's okay. I've been the same way, what with all the trees here in Nashville deciding to plaster us in a coat of wonderful, yellow pollen.

In all seriousness, though. I have heard of leaky seals resealing, as I'm sure you have. Not so much with intake seals, but o-rings and the likes. I've also seen exhaust gaskets fix themselves (due to expansion after heating up.)

My 66 Mustang has a horrible exhaust leak when it's cold, but after the engine warms up, it goes away.

The only thing I can assume, if it is a leak, is that it's insignificant enough that the warmer weather may be causing it to expand enough to seal itself up. Of course, you're running NWP's spacers, are you not? I can see this happening very easily with the silicone-based sealant used on the spacers.

Thanks, Punk. I appreciate your comments on this issue.