what is it with rough idle on a Q?

[longrunQ]

I am just observing that majority of the complaints about the early q concern rough idle.

Well, I'll be abe to tell my girfriend that all the early qs have this problem, not just my car.

[maxnix]

No, instead tell her that only poorly maintained early Q's with dirty intake systems have this problem.

[PalmerWMD]

I have been in Q45etchs car (230,000 miles then I think) and it idled perfect.Couldn't tell it was on.

My Q was almost as good as that for a while.I probably need to look at another TB cleaning.

Fred...

[longrunQ]

No, instead tell her that only poorly maintained early Q's with dirty intake systems have this problem.

nobody seems to ever have the conclusive answer and it seems too many things on the q can cause rough idle: intake, mounts, injectors, driveshaft,tires.

[Q45tech]

The only things that can cause a rough idle [standing still] are fuel or air or ignition related just like all cars...having too much or too little of each.They are one of the easiest to diagnose compared to a Lexus thanks to the Consult. It's just that there are so few QUALIFIED Technicans familiar with them [those that work on at least 1-2 a day [300-1,000 different ones per year].......not many techs at a dealer has that experience!

Smooth stable idle is a badge of honor [and competance] on a 239,000 mile engine just proves its possible. Give me 4 hours and assumming it's not structurally damaged or has bad injectors or worn out rings and valves from ABUSE it will idle properly.

I'll do it for free if the owner agrees to EAT all the dirt that I remove. We could use biodegradable paper towel and let all the solvents evaporate see how you would idle with all that dirt inside you.In a machine world humans would be the slaves.

[PalmerWMD]

In a machine world humans would be the slaves.

Good to see you are getting into that Haloween spirit tech.

Fred...:firedevil

[Q45tech]

Every model and make I studied [looked at lots of them from Accura to Toyota] all have need of cleaning at regular intervals, all have roughly the same problems.....injectors, crank angle sensors, TPS, spark coils, EGR, O2, etc, etc.

Seems unfair to single the Q for abuse.

[VimyJ]

Nissan engines are renouned for their engineering, performance and reliability. The only hiccups in their record were the unforseen premature failure of the plastic chain guides in the very earliest Q45 and some nasty Maxima fuel injectors a few years ago. However, the industry as a whole suffered somewhat from the use of that particular chain guide material during that time.

Don't worry too much about this rough idle. Once it had been figured out, you won't have much to worry much about the engine. Your main concern will then be with the transmission and front rotors.

[silkysmoothyjud]

Yess, yes, effen injectors, freakin brake pad clips go bad.....

[maxnix]

Yess, yes, effen injectors, freakin brake pad clips go bad.....

Both of which are wear items.

Q45tech's well maintained clean injectors have lasted 330K+ miles.

[Q45tech]

No they didn't.2 failed [replaced 4 in odd bank] last May [2008] at 316,000 miles, now 2 more are failing on the even bank. At 323,000

The injectors started failing 6 weeks after E10 was introduced in Georgia gasoline. Since then we have replaced multi- hundreds of Q45 injectors whereas 1 per year was high in the previous 10 years.

At least I know brand new oem injectors will last 1 year and at least 7,000 miles in the presence of E10.

[paranoidjack]

No they didn't.2 failed [replaced 4 in odd bank] last May [2008] at 316,000 miles, now 2 more are failing on the even bank. At 323,000

The injectors started failing 6 weeks after E10 was introduced in Georgia gasoline. Since then we have replaced multi- hundreds of Q45 injectors whereas 1 per year was high in the previous 10 years.

At least I know brand new oem injectors will last 1 year and at least 7,000 miles in the presence of E10.

Tech, could you briefly elaborate on "are" failing? How did you diagnose this, and what led you to investigate?

I'm curious, because I just reassembled (with great regret) my injector rails when doing my KS's. I wanted to send them to Deutscheworks but didn't have time or money to do so, and will be in there soon I presume to reassemble. I'm hoping for a large change after 180k miles. Some of the pintle caps were bad, and the injectors looked filthy, seen here:

http://www.youtube.com/watch?v=plbvv77tKHk

I'm just curious to see what makes you say they "are" failing.

[Q45tech]

I have a jig that plugs into injector harness as it comes off engine making it fast and easy to read injector and knock sensor resistance.

I usually measure my injectors evey 2 months after the failures to graph how the new and old ones are doing. How they increase in resistance from 12.2 ohms from E10 swelling.

[paranoidjack]

I have a jig that plugs into injector harness as it comes off engine making it fast and easy to read injector and knock sensor resistance.

I usually measure my injectors evey 2 months after the failures to graph how the new and old ones are doing. How they increase in resistance from 12.2 ohms from E10 swelling.

But, what about the ones you say ARE failing? I've never replaced injectors on my Q, or any Q. Did you feel it while driving, or did you just ohm both sides when you just recently replaced one bank and determine some (although performing fine?) were on their way out?

[silkysmoothyjud]

2000 Q's dont have that problem, isn't it the coil packs that are probs in the third generation?

[jimbyjimb]

Perfect example for you: Yesterday I had a consistent partial miss in the morning, even after warm-up and 15 miles of highway use. 8hrs later I had no miss and, after getting home, ohmed my injectors. My voltmeter with the new harness plugged in reads all of my injectors at roughly 13.6 ohms, I verified this when I ohmed the injectors unharnessed at 12.1 ohms, then plugged in my brand-new harness and got 13.6 for all injectors exactly 1 and a half months ago, including one brand-new injector that also read the same as the others. Cylinder 3 injector read 16 ohms yesterday while all others read 13.6. It's on its way out. Intermittently non-functional and abnormally high ohms, a telltale sign. If you start getting a bouncy feeling or a detectable pop on cold starts it's time to whip out the ohmmeter. If you have a bad one on a g50 pray its one of the easy to get to injectors, unlike both of mine have been.