Check engine light comes on and off

[hkchuen]

Sometimes my check engine light goes on, and then it will turn off by itself... do anyone has an idea what is wrong?

[Defiant]

Have the codes read by a shop, or in some places Auto Zone will read it for you.

[yodawill2000]

Mine did that and it was an EGR error.All I did was clean out the tubes that go from either side of the manifolds to the egr at the rear of the engine. Both sides were plugged solid at the manifold end. Does the light come on when you going about 50 ? then go out shortly after ?

[hkchuen]

I have just gotten my CEL code checked. The only code that appears is the knock sensor... which should be unrelated to my problem. The following are the symptoms:

(1) The CEL light may comes up at startup. At that time, the car shakes and idles around 500rpm. If I restart the car, someitmes the CEL may go away.

(2) THe other occasion the CEL will come on is when I am on the freeway and step on the gas. The car will downshift to passing gear and then suddenly lose power; then the CEL comes on and will remain on for a long time. At that time, the car will shake; it shakes the most at idle.

(3) Even when the CEL is not on, the car runs very sluggishly.

(4) The other occasion problem is, when the car idles at "P". The idle rpm may stay at 2000rpm and the engine gives out a lot of noise.

Other information:- new air filter- a bottle of chevon techron put in

[DominickJ30]

Its your knock sensor, get it replaced.

[hkchuen]

Thanks! What is a ball-park figure for the labor cost of replacing the knock senosr and the O2 sensor? I will most likely buy the parts myself.

[yodawill2000]

I had KS issues and it turned out to be crud blocking flow to the radiator. Running warm will cause knocks.I loosend the top bracket and pulled it back a little to see between the condensor and the radiator. I was shocked how much stuff was in there. Havent had a prob since and its been about 100/105 for the last 3 weeks here.What Im saying is the sensor might be doing what its supposed too. Retarding the timing.

[bwhan]

Hi, hkchuen...

I heard that the knock sensor replacement is really labor-intensive.The price of the knock sensor itself is not expensive (~$20/each,there are two knock sensors on J30).

When I got a quote from several mechanics, they said it is kind of6 hours job (and you can calculate how much it is around your area).

For me, it turned out not to be a knock sensor problem.(I had Mass Air Flow sensor error code, too. And I replaced MAF...)

Good luck on your J30 !!!

[NismoChi]

The knock Sensor is more like $60-$80 and there is only one on our car.And it is located under the IM, on top of the block. And yes, it is very labor intensive.

[yodawill2000]

Ive heard yanking the plenum isnt hard , just time consuming. I personally will avoid doing it as long as I can.

I might add .. a knock sensor will NOT trigger a check engine light.
Modified by yodawill2000 at 8:00 AM 8/22/2006

[hkchuen]

Just got back from the dealer.

They say that the problem is caused by bad fuel injectors. Does it mean that I should do a "fuel injection cleaning" or should I replace the fuel injectors?

[NismoChi]

A couple bucks for a fuel system cleaner wouldn't hurt, but i doubt it would fix the problem. You'll probably need to get a/some new injectors. Did they tell you wihich one? are you going to do it yourself? It is not that hard.

[yodawill2000]

A quick check with a volt meter will tell ya if the electric part of the injector is bad . but not if the jet is clogged.Ive heard a stethescope is even quicker as the solenoids put out an audible click when working properly.

FYI I just replaced a bad injector and the cheapest I found was 85 Bucks. EACH.

[hkchuen]

The dealer refused to tell me which one is bad; they want to replace all 6 fuel injectors, quoting me a price of $1883, which includes 6 hours of labor.

They also say that it needs "cam seals valve cover gasket crank seal" because the car is leaking oil... is this cheap to fix? Do I need to fix it?

Bottom line is, the service manager walked out with the used car manager and told me that they are "willing to take my car for free" so that it is "more convenient" for me!

I figure it is probably the last time I am going to the dealership. My goodness!

[yodawill2000]

Thats rediculous.fuzzycats.com has the how to for injectors.

He also has a thing about leaking oil.Oil pressure sending unit if I recall.Both are DIY things.Take your dipstick out and see if the oil smells like gas. That was how I knew mine were leaking.If all 6 injectors were bad it wouldnt run much at all

[hkchuen]

Thanks! I called the dealership on the phone again. This time they give more information and said that all the injectors look good on the ohm test. He said that they give the right resistance.

However, he said that the "seats" for the injectors #1, #3, #4, and #6 are bad.

I have never heard of "seats" for injectors before. What are those?

[yodawill2000]

rubber O rings ..I got a full set from a local infinity Dealer parts dept for cheap.The problem is its easy to destroy a Injector getting it out .Check out the DIY at fuzzycats.com to see what it takes.Theres a lower ORing that keeps fuel from leaking into the Cylinder and an upper ORing that seals it from the top.If the top seals were bad you would smell it/see it pool up around the injector.If you dont smell fuel on your dipstick your lower ORings arent leaking.

[NismoChi]

They probably got the code for the "injector leak", if they said the ohm test came out OK, then your rubber O rings that the injectors "seat " on are bad, those are cheap, well, at least the parts. But i was looking at your other post, you said you got the code for the knock sensor, did you clear it or did you tell them about it?If you are going to replace the O rings, put in a new knock sensor, too. You'll only be a few steps away.

[yodawill2000]

Trust me . If they are leaking into the cylinder you will smell gas in the oil. Also theres the danger of hydrolock when you start it.A cylinder full of gas will bend the valves if it makes a stroke.If its a slow leak it will seep past your Piston rings overnight.Thus the smell of gas on your dipstick.Mine was quite obvious. Wife thought I was nuts changing the oil every two days until I replaced the injector. lolNot gonna ruin my baby.

[hkchuen]

Thanks guys. Yes, I think I am also getting a knock sensor code. I have attached below the small piece of paper that the service manager gave me (I basically have to force him to give me this; when I asked him what code the engine gave, he told me "something to do with the mixture" like P0XXX... and then I told him my car is pre-1996 so the code should have 2 digits instead...)

then he went in and gave me this little piece of paper:

[Defiant]

If they are leaking into the cylinder you will smell gas in the oil. Also theres the danger of hydrolock when you start it.A cylinder full of gas will bend the valves if it makes a stroke.

Well, it can bend a connecting rod, or break a piston. But if the valves are seated, you can't get a force on them to bend, and if they're open, you won't develop a hydrolock. Jumped camshaft timing is where the valves will bend, when the pistons kiss them.

Awfully kind of the dealership to offer to take the car for free. I'd have asked them if they'd like a hand in collecting on their fire insurance.

Time to seek out a local independent shop who'll do an Infiniti (like a Z shop).

[DominickJ30]

I might add .. a knock sensor will NOT trigger a check engine light.

You're kidding right?

[gr8scott72]

The knock Sensor is more like $60-$80 and there is only one on our car.And it is located under the IM, on top of the block. And yes, it is very labor intensive.

Actually they are $129 each on everything nissan/infiniti.

[yodawill2000]

I was told a knock sensor will throw a code on the ecu but will not cause a cel ..Is that not so ?My cel wasnt lighting but I felt like I was running on 4 cylinders.(after warm up)Pulled the codes and got a knock sensor.

[NismoChi]

Actually they are $129 each on everything nissan/infiniti.

Look harderhttp://cgi.ebay.com/ebaymotors...wItemhttp://forums.maxima.org/showthread.php?t=487731 Also, yodawill2000 was right, According to the FSM, knock sensor will throw a code but WILL not cause a CEL.

[hkchuen]

A friend's friend (a mechanic) promised to help me change fuel injectors and knock sensors... I need to buy the relevant parts though.

[1] Where can I buy 6 fuel injectors cheaply?[2] Thanks for the link for the knock sensor... is there 1 KS in the car or two?

Are there any other parts I need to buy?

Thanks!

[gr8scott72]

A friend's friend (a mechanic) promised to help me change fuel injectors and knock sensors... I need to buy the relevant parts though.

[1] Where can I buy 6 fuel injectors cheaply?[2] Thanks for the link for the knock sensor... is there 1 KS in the car or two?

Are there any other parts I need to buy?

Thanks!

Cheapest injectors i've found http://www.autopn.com/store/pc...28451

[yodawill2000]

Thats a good price ..I got new OEM matches at autozone for 85 .But I didnt pull the plenum, and I dont think they would take the one I yanked as a core If I had that tool Carlos used I bet I could yank it in one piece.But if your mechanic plans on pulling the plenum , taking out the fuel rail is easy and the injectors will be ALOT easier to pull/push out.