95maxima - codes MAF, EGR and knock

nissan
maxima

#1


The motor knocks on the lightest throttle openings.



The engine almost dies after sitting in gear at a redlight for more than 30 seconds.

The only cracked vacuum hose I could find was actually only a vent hose to the front valve cover.



No signs of vacuum leaks from what I could see - The PCV hose looks intact.


#2

I should also say that the CE has been on for a while but these symptoms only recently started. There had been no previous divability probs since the car was purchased about 2 months ago.

205K miles. GXE.


#3

If the check engine light is on then the computer has stored error codes.
You need to get the code(s) read. Post them here. They have the form P0123.

Has basic maintenance been done, as specified in the owners manual?


#4

Codes are
http://boredmder.com/ecucodes/index.php?year=MY1995&DTC=p0100 MAF
http://boredmder.com/ecucodes/index.php?year=MY1995&DTC=p0325 KNOCK
http://boredmder.com/ecucodes/index.php?year=MY1995&DTC=p0400 EGR
All the maintenance is up to date.


#5

Everything I am reading says the knock sensor WILL require replacing and then the standard Throttle body/ EGR passage and MAF general cleaning. Will this likely be the starting point?


#6

You generally do a repair in the order in which the codes appear.
In other words, the MAF first, clear the codes, and see what happens.

I’m not real convinced that all 3 of these things would be bad and a visual inspection for vacuum leaks is not a reliable method at all. The best method is to connect a vacuum gauge to an intake manifold vacuum port and go by the gauge reading.

An engine bogging down after idling a bit could be due to a vacuum leak or possibly a leaking fuel pressure regulator. The former could be behind the reason behind the codes.


#7

The best method is to connect a vacuum gauge to an intake manifold vacuum port and go by the gauge reading.

So what is the process for identifying the bad hose if the gauge reads low?


#8

I always thought they displayed in numerical order. So your saying replace the most expensive part first?


#9

At this point I’m not saying replace anything but I was always taught to take the first code in line and sort that one out first.

If a vacuum gauge shows a problem then one has to start pinching off vacuum lines one at a time while watching the gauge.
If there is a vac. leak the gauge will show it instantly and then it’s a process of elimination by following the vacum line that has been pinched and which has eliminated the leak.
Point here being that a vacuum leak could be behind all of these faults.

I’m a huge fan of vacuum gauges and if you a lot of your own work they’re one of the cheapest and best tools in the box. Seconds to connect, easy to read, and can tell you so much about what is going on with an engine.

A vacuum gauge is even a fantastic tool to take along if you’re considering buying a used car. A thorough inspection of a used car is always preferred but sometimes it’s simply not practical to disassemble things; nor will the car owners let you do this.
However, it’s a simple matter to quickly connect a vacuum gauge to an intake port and within seconds you can tell if a mechanical fault with the engine exists or not.


#10

Got the gauge. I don’t think thats gonna offer much. With the way its idling now - slow and erratic, It can’t be anything but low.


#11

I will start with replacing hoses - but this car has lots of them :confused:


#12

“So your saying replace the most expensive part first?”

Try cleaning the MAF first

“I will start with replacing hoses”

I see no point in doing that.

Does this engine have big plastic tubing between the air cleaner and the throttle body? That could be cracked.
This is also the area where the MAF sensor is located.

You can also look for vacuum leaks by spraying starting ether or certain other aerosols (can’t remember which right now) around hose fittings or manifolds.


#13

I remembered last night about using carb cleaner around the TB base will normally identify where a vac leak is. I will probably start with that. Someone on the nissan forum also said if the two large hoses to the aircleaner body are off or cracked it would throw a code. I will start with replacing those bc they look old and cracked.

thanks


#14

I think the resonator assembly http://www.courtesyparts.com/16580ra-resonator-assy-maxima-a32b-1995-p-128951.html?cPath=1783_1784_1800_1803&
is leaking air right past the MAF.
Now just finding one other than the 100$ the dealership wants.


#15

Time to hit the junk yards!


#16

Yep, calling now. But we are in a small town. Hopefully someone can comeup with something.

Thanks - I might be back if this rascal continues to be a B*th.

At least I got the control arm fixed ( see http://www.nissanforums.com/a32-1995-1999-chassis/155874-replacing-rear-valve-cover-gasket-i.html ) for 65$ (plus 140$parts) instead of the 400 the local tireshop wanted.


#17

Have you checked the 02 sensor(s)?


#18

Not as of yet. But with the drivability issues, (which just started all of a sudden - even though the CE has been on for 2 months), I dont think that is the cause. It might be a factor.

For the first 1.5 months of ownership, it was probably getting about 19mpg of strictly city (and I mean 20-25mph avg) driving. O2s normally will crater MPG if they are faulty.


#19

O2 sensors don’t cause drivability problems.


#20

I could see how they could cause some sluggishness if they were bad. They probably would be allowing it to be real rich at idle and that could cause it to kind of be soggy right as you leave a light. But again, I would think theres something causing them to get sooted up and that would contribute also.