MaxDD

I was curious about testing injectors on 4th gen Max's.
What ohm range is within spec?
Also, are there tips/links that show how to access all the injectors?
I want to make sure she's running 100%.

Thanks!!!

DennisMik

iTrader: (2)

The resistance of the fuel injector coil is 12 - 15 ohms if I remember correctly. But measuring resistance is maybe a third of a full check. All it will tell you is that the solenoid coil is OK. The mechanical aspects remain unchecked.

You won't know if the injector valve is opening all the way, you won't know if the injector valve is closing all the way, you won't know if the pintle cap is cracked and/or missing. You need to remove the injector to do these inspections.

With the help of the wiring diagram, you can check the rear injector resistance by unplugging a wire harness connector and measuring through the harness. It would give you some nice-to-know info, but if the engine is idling smoothly, you have all the information you need.

I don't want to discourage you from learning something about the car, but you are placing more importance on the resistance reading than it really gives you.

MaxDD

Car is automatic with 102k miles, fully stock.
You can't physically feel a misfire at idle, however if I have car in drive and let it roll forward under it's own power there is a slight misfire/stumble.
If I pull the throttle cable with the hood open while car is running, I can feel/hear a stumble in the lower RPM range.
Also, where are the "coils" on these cars? Not to sound stupid, but the injector has a harness on top of it, but I don't see a coil (I'll inform you I'm used to the coil packs on Z32's so that's what I'm used to seeing).

CS_AR

Can you provide some service history for spark plugs, fuel filter, fuel pressure regulator, and other items that may have been recently replaced?

There are so many things that can cause a slight stumble that without seeing the car or being able to run some diagnostics, we're just making some educated guesses.

The coils that Dennis noted are inside the injector body -- under the round black barrel looking part under the red top in the picture below. I had a flooding problem with a misfire on cylinders 2 and 5 that was cause by broken pintle caps that are in the picture below. My injectors always Ohm tested properly, but as you can see from the picture I had broken pintle caps.

A few months ago, I spent quite a bit of time and money working through a handful of symptoms that were hard to pinpoint.

[IMG][/IMG]

MaxDD

The car has been family owned for quite a few years now, and just last year was handed down to me. That being said, I can vouch for things I've done in the past several months:
New fuel filter
New gas cap
New o2 sensors (all 3)
Other than that, I know my parents DID have a cam sensor replaced, as well as (I believe) one injector. I don't think the FPR or any other fuel components have been replaced.
I'm assuming the top intake plenum has to be removed to get to those 3 injectors, correct?

CS_AR

Correct. Cylinders 1, 3, and 5 injectors require intake plenum removal.

Sent from my Z998 using Maxima

CS_AR

It looks like you have a nice car that will easily deliver another 200K or more miles. I have a 99 Infiniti I30 with ~275,000 miles and a 99 Maxima also. The helpful key word you used to describe the symptoms is stumble.

I've read where a ground inside the Mass Airflow Sensor (MAF) on 4th Gen Maxima/I30 has been reported to corrode over time. The corrosion is just enough to interfere with the sensor's ability to transfer data to the Engine Control Module (ECM) without causing a Check Engine Light (CEL) trouble code to appear.

One way to test for a failing MAF is to unplug it when the engine is stumbling to determine if the problem goes away. If the idle improves, you found the issue.

Over the years I have resolved the issue by either:

1) Carefully cleaning the MAF sensor element by spraying it with CRC MAF cleaner (following the directions on the can) and allowing the MAF to dry before re-installing it and starting the car to test.

2) Replace to MAF with a used one that I picked up from a salvage yard car. I believe there are members that have tested MAFs for sale in the classified section. As the car ages, it is not a matter of if, but a matter of when the MAF will eventually start to fail. I keep a spare 4th gen MAF in my workshop for when the problem surfaces.

NOTE: I have read where members purchase aftermarket MAFs and experience problems. I understand the company that builds the MAF is also the company that builds the car's ECM. So I suspect an aftermarket MAF has some amount of trouble communicating with the ECM.

Other maintenance items to check:

SparkPlugs - Determine when the spark plugs were changed last. Only use NGK plugs. Many members get great results with copper (lower cost) and double platinum (OEM grade) NGK plugs.

Fuel Pump - The fuel pump could be getting weak. Though I don't want to believe this is the problem on a car with only 103,000 miles. However, a fuel line pressure test can rule out a weak fuel pump.

Also, you can search the 4th gen forum for "idle stumble" to find solutions that have been used by other members.

dwapenyi

iTrader: (3)

Before you go servicing your injectors, I would give TC-W3 a try. The main reason TC-W3 came about is because today's environmentally friendly gasolines (no lead etc) have lost their ability to lubricate the fuel system properly. Over time this leads to sticky injectors and whatnot. If, after that, your car still acts funny, then I would look into servicing the injectors.

Also, replace your FPR. If it's OEM, it's exhausted. When you replace it, you should see a dramatic difference in the way the car starts.

https://maxima.org/forums/fluids-lub...itive-new.html

CS_AR

Exactly! I tried TC-W3 and it works.

MaxDD

Thanks guys, solid advice!
I've been "working" on my cars for years, and want to understand this car better so I can make it last, as it's my DD (hence the SN).
I'll def get a new FPR. How sensitive is this car's fuel system? Does it need an OEM fuel filter as well? That's the worst job to change such a "simple" part, UGH!

dwapenyi

iTrader: (3)

The FPR is a simple, vacuum driven, mechanical device. Because of that aftermarket or oem is fine either way.

The fuel filter is even simpler. It's just a filter. Aftermarket or oem, doesn't matter.

CS_AR

If you decide to replace the FPR, you may want to replace the Phillips head screws with some Socket Head Cap Screws - M5-0.8 16mm and M5 lock washers. I get Hillman Stainless Socket Head Screws from Lowe's or Ace Hardware. You can see how I replaced all of the Phillips head screws associated with the fuel system in the picture below.

MaxDD

Dizzamn! My engine looks nothing like that, good work!
I think I found part of my issue:
Currently has NGK BKR5EGP plugs in it, and from what I've read it should have PFR5g-11.... correct??

dwapenyi

iTrader: (3)

Another good reference site for Maximas is VQPower.com

From the link below you can see that those NGK BKR5EGP plugs are the copper plugs substitute. They are fine so long as you change them every 30K miles instead of the 60K miles specified for the original NGK platinums.

http://vqpower.com/v3/content/changing-spark-plugs

MaxDD

Excellent, thanks again! I know there's a lot to be learned about this car.

MaxDD

So, the new plugs (PFR5g-11) came on Saturday, took out the old BKR5EGP. First 5 looked ok, nothing abnormal. Then, on the final plug (cylinder #5) I found the entire plug hole filled with oil. I changed the plugs as planned, and have driven the car since Saturday. I have noticed improvements, such as smoother shifting, more solid idle, and overall smoother drive.
My plan is to look at that cylinder again next weekend, and see how "bad" it is.
What am I looking at here, probably a leaking valve cover gasket?
Any tests/inspections I can do?
Thanks in Advance

CS_AR

There is a rubber grommet that sits on top of the spark plug tube to keep out oil that is circulating in the Valve Cover (VC). As the engine ages, the VC gaskets and grommets become brittle or shrink resulting in oil leaks. A VC gasket kit comes with gaskets and spark plug tube grommets.

I use Felpro gaskets (blue) as you can see in the picture above. I usually order Felpro gaskets from Advanceauto.com and use the TRT30 coupon code for 30% off and specify my pickup at my neighborhood store to avoid shipping charges. I've replaced VA gaskets and grommets on all three of my 4th gens as mid-life maintenance items.

MaxDD

Ok, thanks.
I didn't see a "how to" for replacing the VC gaskets, is there one available?
Also, as a first time do-er, how long can I expect this to take?
Other items to replace, or look out for before/while doing this maintenance procedure?

dwapenyi

iTrader: (3)

Look for instructions for removing the upper intake manifold (UIM)

Also it's a good opportunity to clean the throttle body, replace the PVC and FPR, clean the IACV.

Nturner

Here is a link I found to a collection of you tube videos for different repairs. https://www.youtube.com/playlist?lis...5576EEB4A0F7E5