Mechanics

ENGINE MISFIRE PROBLEM

Nissan Altima

I have a 1993 Nissan Altima 2.4liter engine. Developed a miss and did a full tune up. Plugs, wires, cap, rotor, fuel filter, compression test all @160psi. No codes at present time. Number 3 cylinder missing at idle and seems to clear up over 2500rpm. Replaced injector checked for vacuum leaks still same problem. O2 sensor is showing rich all of the time at idle and.5 volt and will go into operation as it normally should as long as rpm stays up. Once rpm is lowered miss returns. Any help would be appreciated.

Thank You,
Fred
Avatar
Randomorbit3
May 21, 2007.




There could be a problem with your connecting rod or piston. If it shows no codes, and you've replaced everything you can replace next to the ignition, you said it's also running rich. If you feel comfortable pulling your valve cover to check for wear and tear and even popping the head off and pulling out pistons to take a look, I'd say it'd be a good idea. If not, definetly have a good engine shop take a look at it.

Tiny
KaMo
May 22, 2007.
Dear KaMo,
I am a shop owner and there is no bottom end problem. Like I said the engine has 160psi compression and no noises from the engine except the misfire. Everything has been replaced including the fuel injector. My scanner is showing rich at a idle until the engine reaches approximately 2000rpm and then it is somewhat firing and the O2 sensor starts reading correctly. There are no vacuum leaks anywhere. I have also used a NOID light and the injector is getting a triggering signal from the ECM. I have 30 years working as a mechanic and shop owner and am figuring that there is something that I am missing. Trust me I do not usually run into something that I have to ask assistance on and it is usually the other way around. I have checked the pulse width on the injectors etc. I have also performed a leak down test with no problem there as well.

Thank You for your input but that is not the problem and that I can assure you.

Fred

Tiny
Randomorbit3
May 22, 2007.
Morgan,
Thanks for the idea but like stated before EVERYTHING is fine except only one cylinder, number 3 is misfiring. If I retard the ignition it will retard ignition on all and the engine will have less power and run hotter. And the timing is right on the money. Cam timing is right on the money as well. That would also tell you that valve adjustment is on the money as well. Even thought of carbon holding the exhaust valve party open and the is not he case either. Any other ideas other than what I already tried? I was hoping a Tech would have run into this before and could assist. Even if it was a different cylinder.

Any other possible ideas? I am open to any and all.

Hey, Bob or Ken do you have a idea that I have not tried? You know, Pro to Pro?

Even tried talking to some of the Tech's at Nissan and they will not assist shop to shop. No friendly Nissan Dealers down here I guess. I assume that if I took it in for them to work on it things might be different.

Thanks,
Fred

Original Message
From: Morgan Failure [mailto: krackrocksteady@gmail. Com]
Sent: Sunday, May 27, 2007 4: 56 PM
To: randomorbit3@verizon. Net
Subject: Re: Engine Misfire Problem

Have you tried retarded the ignition at all?

Tiny
Randomorbit3
May 28, 2007.
My 2cts, Won't hurt to check these areas

The O2 sensor reads unburned oxygen in the exhaust, and generates a voltage signal that is proportional to the amount of oxygen in the exhaust. The signal can vary from a low of about 0.1 volts up to a high of about 0.9 volts. A low voltage signal indicates a lean fuel mixture. A high voltage signal indicates a rich fuel mixture. The engine computer uses the O2 sensor's input to balance the fuel mixture during closed loop operation. A bad sensor may prevent the system from going into closed loop, and usually causes the fuel mixture to run rich causing an increase in fuel consumption and emissions.

A lean mixture in a single cylinder can be caused by a leaky intake manifold gasket, air leakage past injector O-rings, a leaky EGR valve (if the valve is adjacent to the cylinder intake port) or a dirty, plugged or inoperative fuel injector. Loss of compression because of a leaky (burned) exhaust valve or a leaky head gasket

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

Tiny
Rasmataz
May 28, 2007.
Dear rasmataz,
Thank You for your response about my problem.
Please note all other posts that I have included with this problem. I think you will see that all of the bases that you mentioned have all ready been covered and then some. Yes, it is going into closed loop as well. Egr system checked as well. The spark is blue-white and the coil, pick-up, module and CPU have been checked as well. My scanner is a Snap On Modus.

Any more ideas?

Thanks,
Fred

Tiny
Randomorbit3
May 29, 2007.
Fred-I'm convinced its fuel related problem. Try rechecking the injector for no.3. You got me going on this-its a mind breaker. Am thinking of fuel injection duration-but not so sure were dealing with one cylinder, /fuel trimmings/reflashing.

If resistance is not within specifications (typically 3 to 5 ohms for a low-resistance injector, or 12 to 17 ohms for a high-resistance injector), the injector needs to be replaced. A difference of only 1 ohm less than specifications may be enough to prevent the injector from opening reliably under some operating conditions.

Note: Injector resistance typically increases a couple of ohms as it warms up. Therefore, you should check the values twice: Once when cold and once at normal operating temperature. If resistance goes out of specifications when hot or cold, replace the injector

I'll find some more and get back to you

Good Luck[/quote: 4195281f16]

Tiny
Rasmataz
May 29, 2007.
Dear rasmataz,
If I already had not just replaced the injector with a new one and not a reman I would agree. Condition has remained the same though. Plugs 1, 2 & 4 are starting to burn brown and #3 is black but not any raw fuel odor. It is doing the same thing with the old injector as well as the new one. I did check pulse width but after so many things I do not remember what it was. I can tell you that it must have been with in specs or this conversation would not be taking place. I almost want to think that the exhaust valve is staying partially open due to carbon coming across the vale face when hot and cracking off when cold? I know it has to be something stupid or blatantly in my face that I am missing it.

I love a mystery but not when it is mine! I am still laughing but this is very frustrating to say the least. Maybe you will come up with something that I forgot to do or try.

Let me know if you or anyone else has a idea.

Thanks,
Fred

PS: rasmataz, if pulse width etc. Was affected then wouldn't the others be affected as well? Oh, and there are no broken wires etc. At the injector.

Fred

Tiny
Randomorbit3
May 29, 2007.
About the pulse width I was hinting on it, that was my question on the duration-it should affect all.

Anyway try a voltage check KOER on no.3 injector brown/yellow wire at pin 103 should read 11-14volts.

Am allready confuse and when I get to this point I go back and check everything step by step-new or old stuffs within the compression/fuel /ignition system. Like you said it just probably something that you're missing it.

If it was me I'll scope it to rule out the ignition system

Tiny
Rasmataz
May 29, 2007.
HEY RAS.I AM VERY ANGRY AT U.U RAN INTO A PROBLEM LIKE THAT AND WON'T EVEN LET ME KNOW. THAT'S PRETTY UNJOHN WAYNE MAN.
OKAY SHOP OWNER.I AM A SHOP OWNER TOO.I'm L1 certified and also nissan heavy on repair.I was struggling with a 90' 300ZX for a day with similiar problem but without OBD2 data stream. Now do this. Throw away the noid lite. Junk. It can't tell how long is the pulse. What kinda voltage kick or when pintle open. Same for coil as compare to a good cylinder. How ur know u are getting a good signal and a good voltage/amp. Set ur scope on 4 channel.
2 on the bad cylinder ignition and injector pulse.
2 channel on a good known cylinder. Compare voltage and low amp probe. Whatever u've got do the same thing at the computer output end.
Bet u have either bad connection or bad wires.
I had a bad connector on the ignition coil and no matter how I look at it physically.I can't find the flaws. But I trust my scope and nail that problem after 1/2 a day of losing hair.
Email me if u have toi'll walk u thru the wire man
heeee hawww

Tiny
Kin chan
Jun 10, 2007.
To One And ALL,
THANK YOU!
Even after doing compression check, coolant system sniff test (Looks for CO's in the cooling system), which showed CO's in the coolant. Then we had no choice to condemn the head gasket. This sucker was just barely leaking back and forth between #'s 3 & 4. Even though # 4 was firing and # 3 was not.

Once coolant showed traces of burnt fuel in it I went and pulled it down because I knew it had to be there. And low and behold it was. Once cylinder head was checked to be true as well as the block Humpty Dumpty was put together and I am now happy to say, Purring on ALL 4.

I knew nothing was showing up as far as electrical or fuel so it had to be only one other place. So now if anyone else runs into this problem I suggest they invest in a cooling system sniffer and am kicking myself in the butt for not even thinking about this old and hardly ever used tool. I might have used it now 4 times in 20 years.

So now we can say, " Case Closed and Mystery Solved"!

Again, THANK YOU ALL,
Fred
AD

Tiny
Randomorbit3
Jun 11, 2007.

AD