Idles Rough

Oooh...A test! My guess would be either a bad injector or an injector wiring/harness connection problem. If you do the ol' "screwdriver to the ear" trick does the injector on that cylinder make the typical clicking noise at idle?

I have a 95 Maxima and recently got a tune up just because it was time. The next day the car started running rough so I took it back to Pep Boys where I got the tune up and they saw nothing wrong. The condition has worsened so I took it back to Pep Boys Saturday. They checked the spark plugs and they were fine and did a diagnostic and there are no codes coming up, but they know it is something misfiring with the injection system. They said they cannot do individual tests on the 6 injectors and I would need to take it somewhere else. What should I do next. Any help is greatly apreciated.

Ok Class,

I know it is not 7 p.m EST but my Tampa Bay Lightning are in the Stanley Cup Finals and game 1 is tonight.

Ok here goes.

Things that can cause a lean cylinder missfire

A clogged/non working injector would definitely cause it , but it is not the case with this car.

Good answer by the way, at least you are thinking about it.

Think about this for a moment

What else can cause it .....

Lets define a lean cylinder missfire.

when the mixture of air versus fuel to a particular cylinder becomes unbalanced (more air than fuel) when the spark plug goes to ignite the mixture there is nothing to burn, the over abundance of air and depleted the fuel charge so there is no burn, hence the missfire.

so , one would next investigate a vacuum leak to that particular cylinder.

So th>

Good Job Steve !!!

Better question what should you have done first? NEVER take a car to pepboys for service!

My guess? They used bosch platinum plugs which are useless junk..

I should have mentioned that I am no mechanic AT ALL, so excuse me for going to a chain type of repair shop that I thought was decent. I am on this site for genuine help, not for criticism of where I have taken the car or the type of car knowledge I should of been born with. Moving along... they checked the spark plugs and they are fine and I saw them check them, so to repeat myself, what should I do next?? I am a mother of three boys and would like to know how I can fix this myself if possible. Thanks to those who want to help and maybe I won't go to Pep Boys again, so thanks for that advice.

I should have mentioned that I am no mechanic AT ALL, so excuse me for going to a chain type of repair shop that I thought was decent. I am on this site for genuine help, not for criticism of where I have taken the car or the type of car knowledge I should of been born with. Moving along... they checked the spark plugs and they are fine and I saw them check them, so to repeat myself, what should I do next?? I am a mother of three boys and would like to know how I can fix this myself if possible. Thanks to those who want to help and maybe I won't go to Pep Boys again, so thanks for that advice.

Chill out, I WAS trying to advise you on the mistake you made, sorry if you can't take it the way it was meant.. We have cars that drove into those places -towed- to our shop because they killed them and can't even get them running to drive out under their own power! The tire stores are just as bad.

Again what kind of plugs did they use? Maybe to the untrained eye they "look fine" but given the car was fine before they did this work, more than likely it has something to do with the VERY poor quality parts they sell and use. How do "they know it's misfiring due to the injection" yet don't have a clue as to what it is? This is the line they use to shift blame from themselves. They "don't do fuel injection work" so everytime they screw a car up, this is the line they are taught at training school to tell customers. You'll probably never get anywhere with these people, best bet is to find a shop that specialises in nissans and get them to look at it. The money you spent at pepboys was a waste.

Take the car to a Nissan dealer or Japanese specialty shop, and get them to figure out what's wrong. Or, it may be cost effective to just have them do a second tuneup instead of high-priced diagnostic time. (Someone will probably flame me for this bit of advice. It's a gamble either way.)

If it is traceable to something Pep Boys did, then contact Pep Boys' manager and tell him you want a refund or will dispute the charge. (You did charge it, didn't you? It's the only meaningful protection that you have.)

If they won't take off the charge, then follow up with your credit card company immediately. Send them a dispute, IN WRITING, include the second repair bill, and any written statement that you can wrangle from the second shop as to the problem. (It is probably also best to use the same charge card you used at the first shop.)

At least take some delight in the fact that your card company will charge Pep Boys about $25 just to review the dispute with them, whether or not it is taken off your card.

I used to work at Sears automotive department while in school. All these shops are into selling frequently questionable parts, and have just enough skill to slap them into the car.

JM

Aww .. C'mon guys you don't want me to just give you the answer do you ?

That is too easy, besides you won't learn anything

Clue :

Massive Vacuum Leak @ number 4 cylinder ONLY !

Actually... I never offered any diagnostic theories as to what his problem could be... I was just answering his question about injector cleaning. I'm as curious as anyone as to what could be wrong....

let's see.... fuel... spark.... timing... compression hmmmm

Ah, don't take the fun away. I was about to check around cylinder number 4 tonight and report back. I think it's a good HINT.

Been busy with computers, kids, etc at home...and haven't been able to write back from work as our news server is down (I don't care for the google news as it's incomplete).

Bruce

"NissTech" wrote in news:Xc9tc.29434$Ol3.19796 @twister.tampabay.rr.com:

Interesting... I've had some experience chasing down disconnected vacuum lines on my older cars to clear up bad idle. But how does this explain the detected misfire? This really is a question... I wonder how the computer would detect a misfire at #4 if it isn't due to something electrical.

Ok Bruce I won't give you the answer just yet.

Tricks to finding vacuum leaks.

Use a mildly combustible spray (like carb cleaner) around the effected area when the engine is running, if the idle smoothes out you have found your leak.

I expect your diagnosis by Friday evening :-))

An EGR valve that's stuck open at idle can have the same effect as a vacuum leak. So too can the wrong PCV valve (one that flows too much air for the application), or a loose PCV hose. The rough idle in these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all. Lean misfire will show up as elevated hydrocarbon (HC) readings in the exhaust?enough, in fact, to cause a vehicle to fail an emissions test.

Lots of info on lean misfires (including the above quote) at:

JM

I'm not so sure about that one on a FI car. This extra air is still going through the MAS so the computer would add fuel for this air. It's just bypassing the throttle plate via the crankcase. For it to lean out the engine, it has to be air that never passes over the MAS. Plus most cars have a centrally located PCV valve so even a broken hose isn't likely to

-kill- one cylinder like the OP stated, nor would EGR for the same reason, it would just polute the whole engine with exhaust, not one cylinder.

Now a brake booster is another story. Most of them do attach to the intake near one hole and a leaking booster can cause a cylinder or two to go dead at idle when the brakes are applied.

That sounds like a good analysis to me. So we're left with, what? Leaking gasket, or injector o-ring?

JM

Well Bruce

What is you Diagnosis ?

it is 7:49 p.m EST

I'll look again in another hour

Vac hose that goes near that cylinder or as I said a bad booster. Could be a blown out intake gasket, some nissans have been bad about that in the past. Might be a dead injector or as you said an injector seal? Who knows!