Narcoleptic Maxima... HELP!

[Narcoleptic]

She's a 95 SE... 69,000miles. The history is a bit weird. About 6 months ago it started acting up... more or less just dying completely and 99% of the time completely without warning. The ECU tells me the Knock Sensor circuit and Engine Temperature Censor Circuit could use some attention. I fiddle around with a voltmeter and everything seems to be fine. The problem is very intermittent and could go a month without stalling. I took it to the local shop with the $75,000 computer. By the end of the day they were scratching their heads, but were kind enough to offer to throw parts at it.

Since I've yet to have any real problem restarting it I declined figuring the intermittent problem would become mittant. And much to my unfettered disgust it did. The engine was acting like it was missing a cylinder ‘cause it was shaking like a pinto on bad Gas. (yes, I only use the good stuff) After an exhausting afternoon looking for electrical reasons I discovered that the injector on cylinder 1 had failed. I replaced that and it ran like new shoes for about another month. The Narcolepsy returned, and a few weeks later another injector failed. Again replaced and ran fine for about another couple weeks until it began to die again. I replaced the last easy to get at injector assuming failure was inevitable. This had absolutely no effect. I know the two injectors replaced already were completely dead. I know earlier generation Max’s had problem’s with failing injectors due to overheating but that was supposed to be fixed on this Gen., wasn’t it? It has now been about 3 months and no new injectors have failed, so I’m kinda wondering if there aren’t 2 separate problems. I have run injector cleaners from more than a few manufacturers and none have helped. (no not in the same tank, usually at least 1 tank between cleaners)

Power is not a problem and doesn’t seem to be effected, and if it were another injector problem I would like to think it would be surging or otherwise misbehaving. Aside from the sudden crashes it seems quite happy.

I have not yet replaced the knock sensor because it doesn’t seem to me that it would kill the engine so quickly. (am I wrong there?) I am hesitating to replace the last three injectors because it might not be necessary, and is pretty expensive. I kind of suspect an electrical short somewhere but I’ve gone over everything I can think to do with a voltmeter and find nothing out of sorts. I’ve even tried jiggling all the wires I can find while testing and still no easily spotted problems. If it is intermittent how can I find it?

Thoughts of any sort are greatly appreciated!

[jayendo]

Your problem could be the ecu it's self.... I've seen dealership mecanics go nuts trying to figure out ideling problems, testing air flows and what not.... and it turn out it's a bad ecu....

[pollochicken]

Is it possible for the knock sensor to be faulty even though the Check Engine light doesn't give that code? My Max was having trouble while idling on a stop and Nissan Dealer told me it gave a Knock sensor code but the Chen Engine Llight never turned on giving that code.

I changed it anyways and at first it still had some trouble at idling but a fter a week or so it stopped having this problem. Now about 2 or 3 months later its having trouble again. Waht's up??? Could it be the Knock sensor went bad AGAIN?

[Narcoleptic]

Spose I should have updated sooner.... The problem ended up being an odd sort of push pull between the Temperature Sensor and the Knock Sensor. (Cause really what else was there to do) When I took it all apart to completely replace Temperature Sensor and knock sensor I discovered there look to be two temperature sensors. One you can buy and replace and another "I don't really know what" which looks to be welded in place but does still have a wire lead meeting the harness? In any case I started fiddling with this ...I'll call it a sensor... the plastic was dry rotted and wasn't holding particularly well. I soldered on a fresh connector and replaced the temperature sensor while I was at it. Given the way the unknown sensor thing looked I took back the knock sensor and decided to wait. I cleared the codes on the ECU and haven't had a problem since. My guess is the sensor(s) were reading one temperature extreme or other and changed the fuel mixture to compensate... but since it wasn't the right temperature all hell breaks loose which made the knock sensor retard the timing ultimately to the point of stall. This is my explanation of the "crash"

I seriously doubt your knock sensor went bad. Your problem to me sounds more like a problem potentially with vacuum or maybe even a failing injector. If you've ever tried to keep your engine running without pinning an open vacuum line it will shake like a pinto on bad Gas. In my case even though the ECU told me "knock sensor" it was not broken it just did what it was programmed to do causing the stall, so my guess is that is why the ECU moaned about it. Is your ECU saying any codes or the just the "no codes" code? The way I trouble shot my injectors was when experiencing a rough idle pull one injector connector (the electrical one) at a time. The engine will either get worse or will not change if you can narrow it down to a single cylinder you may have an answer. Give a good look around for loose vacuum lines and maybe even check your fuel filter?

[pollochicken]

Hey thanks for the reply.

The failure my Max is having when idling is not continuous. It comes up intermitenly. Sometimes it kind of chokes for a second; the tachometer slightly slides 100 rpms downward and then before that second is up it returns to normal idling revs ( 600 - 700 rpms ). It hasn't completely gone dead. The car keeps idling normally after that and maybe a few second or minutes later if I'm still at a stop with the gear in Drive (auto transmission) it will do the same thing again.

I already changed the spark plugs and the fuel filter so that's not it either. I also cleaned the throttle body. Its been doing this since I bought it with 68000 miles on it. Now It has 76000 miles and still has the same problem. although after about a week of having changed the knock sensor it had no problem for about a month and a half.

It doesn't give out any check engine codes for this problems. It is however giving out check engine codes for manifold absolute pressure sensor and solenoid valve but that was ater I installed the Y-pipe. So I'm guessing it has nothing to do with it right? Or should I chenge these also??? Damn its a lot of money!!!

[Thinkster]

Narcoleptic:
You mentioned something about checking your fuel injectors by pulling the connector one at a time. How do you pull the connector? I've tried but can't get that s&$t off! I thought I read somewhere that there is some metal clip that holds it on, but I don't see one.
I'm having a similar problem where the car runs rough and shakes a lot especially at idle. I had replaced my fuel filter & hoses about 3 months ago (unrelated to this problem). My check engine light stays on and the code the ECU spits out is '51' which I believe is: "Fuel injector circuit open". If I could get those connectors off, I think it would be a lot easier for me to measure stuff with my meter & scope.

[Narcoleptic]

Pollo: If the MAP sensor is complaining it's definately got something to do with vacuum. That's all that particular sensor does. Reads vacuum from the intake manifold and reports it to the ecu. Since Vacuum changes with load and speed it lets the ecu adjust the amount of gas and spark as needed to compensate. It's either the sensor itself or a leaky/disconnected/clogged vacuum line. That error shouldn't have to do with your Y-Pipe (so jealous by the way) as that is exhaust side but could be being influenced by your solenoid which I'll get to in a bit. You should be able to diagnose the MAP sensor with a volt meter. Get the value from a shop manual (ply local dealer with alcohol if needs be). Watch the meter as the car runs for a while it should change. Assuming it checks out this far... Once the engine is warmed up you should be able to rev the engine and see a change on the meter, if you don't make sure it's vauum feed lines aren't clogged or crimped or disconnected. If you still can't find any vacuum leaks or problems it's probably the sensor and should be replaced. The solenoid again is to do with vacuum and if I were to start replacing parts it might be the first one I replaced. It basically controls the EGR valve which takes some exhaust gas and recircualtes it for emissions reasons. If it is frozen or otherwise impared it could be throwing off your vacuum as well and could be throwing it off enough for the MAP to get moody which would definately effect your timing. I'm not sure how best to trouble shoot that one.

Thinkster:
I have a 3rd Gen 95 Maxima, on that model there is a plastic clip that attaches to the injector. I just had to depress the plastic buttonish thingy and pull. If you're talking about pulling the injector itself... yes it is a complete bugger. The first one I did, I clamped off all the fuel lines but was too stupid to take the 45 or so PSI off the fuel lines first... It made kind of a bang and covered me (eyes and all) with Gas. Lesson learned. He is wise who can learn from his own mistakes, he is a fool who cannot learn from others....anywho... If you want an even simpler way to trouble shoot the injectors you could get the longest screwdriver you have and place the blade side on the injectors top. Place the other side against your head and you will hear a very pronounced clicking noise while the engine is running - if you find a quiet or slow one you have your injector. Just pray like me the bad ones were the ones you can get to without having to pull the intake manifold.

Hope this helps

[Thinkster]

I guess I should have mentioned that mine is a 3rd Gen (1991) so the injector connectors are most likely different then that of yours which I believe is considered a 4th Gen (1995-1999). But I guess I'll try that long screw driver idea. I've used small wooden poles before to "listen" to various things on the engine, I should of thought of that for the injectors too! Well that's what this forum is for sharing ideas, experiences and techniques...
BTW, how much did they charge to put it on the expensive computer to diagnose yours?

[Narcoleptic]

I didn't end up paying anything. I took it there cause I wanted to know what the dealer would say, assuming if the price was right I would just tell them to go for it. Since they could only offer to throw parts at it I told them I'd be back when it was a bigger problem. They never asked and I never offered money so it's no harm no foul in my book.