Warning: This is a long write-up.

The Car:
1992 Nissan Maxima
SOHC V6
140k miles

Problem description:
Sometimes the car will run on 5 cylinders. The problem comes and goes. It usually lasts between 3-8 weeks, and then magically disappears.

What I have done:
The first time this happened, I pulled the plug wires off one at a time, and found that cylinder #3 was the culprit. I did not suspect the fuel system since I have never seen a fuel injector fail, I ran good gas, and I replaced the fuel filter on schedule. I pulled the plug in cylinder 3, to check it for spark. It had a weak spark and the ignition parts were all original, so I replaced the plugs, wires, distributor cap, rotor, and checked the timing. This did nothing to help the problem.

I then initiated the ECU’s self-diagnostic test. As far as the ECU is concerned, everything is ok.

I looked for any wires or vacuum lines that were hanging loose, but I didn’t find any.

Then I checked the injector harness. I wiggled it around, but that didn’t help. Then I pulled it off and cleaned the connections. That didn’t help either. I measured the resistance of the injector’s coil and it was a little low, but nothing terrible.

The problem went away, so I forgot about it.

The problem resurfaced about a month ago. Now it’s cylinder #6. The problem pointed to the injector again. I tried wiggling the connector, pushing the wires into the harness, and cleaning the connections, all with no effect. I measured the resistance of this injector’s coil and it was open. I figured that I should just replace the injectors since I’ve been having trouble, but I would hate to do that and still have the problem, so I put it off for a couple of weeks. Well Monday the car started running fine.

What I think:
All I can think of is that there is some connection inside of the injector that opened up, and then due to vibration and chance it closed again. Or maybe there is a bad connection in the wiring somewhere. I doubt the bad wiring idea because I can measure a voltage at the injector harness. I think it was almost 12v, but it’s been awhile. Keep in mind that I don’t have an oscilloscope and my meter doesn’t respond fast enough the ‘see’ the fluctuations, but I see something.

What I have:
A wife that wants her car fixed, and a ‘barely used’ set of injectors.

My Question:
Do you think that I will fix the problem by replacing the injectors and/or stumbling across a bad connection in the process?

If not, do you have any suggestions? Is this a common problem?

Thanks in advance,
Jeremy Harvison
http://jeremy.natesnetwork.com

 

If you 3-gen guys need a lesson on how to ask for technical help, READ THIS GUY'S POST! To the point, descriptive and intelligent.

Unfortunately, I'm as frustrated as you for the solution. I would REALLY hate to recommend changing the injectors and finding out it didn't solve anything.

Did you measure the resistance of the injector both when they were working and not working?? ie.. maybe measure the 6th injector now that it's working. If it measures differently, then it would give more indication that it's an injector. I could also be something inside the wiring harness also.

My only other suggestion is to wait until it's not working well again and bring it to Nissan. Have them hook it up to the Consult and have them cycle the injectors individually. Problem is finding a GOOD Nissan tech and the visit will cost about $75 just for the diagnostic visit.

 

Jeff....

i would go straight to the dealer and have the diagnostic run. I had the SAME problems for the longest time and gave up and went to the dealer. My #3 injector was done. All 6 are replaced now and i can't be happier. Good luck...

 

I will take your advice and check the resistance now that the car is running fine. I may also pull the ECU and look for leaking capacitors, which is a common problem with DSMs.

I also plan to measure the voltage at a known working cylinder's injector harness to compare to the offending cylinder's harness if/when the problem resurfaces.

Hopefully I will find a smoking gun.

I don't plan to go to the dealership. I would rather just replace the injectors. I have a set, and I don't mind the work. I'm just gathering info before I jump into anything.

Thanks for the replies, and if anyone else has anything to say please chime in.

Jeremy