Pathy sputtering at idle under load

[jjeffri]

Hello All:

It has been a while since I posted or read the forum, it was down for a little while and I kind of forgot to stop by. But now I have a problem.

 

My 1996 Pathfinder is sputtering at idle. I find that it does this more often when there is a "load" on the motor, but the engine is running at idle (i.e. not pushing the gas pedal). For instance, if I am stopped at a light and the car is in Drive with my foot on the brake (a good place for it to be to avoid moving) the car will stumble like it wants to choke off; however, if I place the transmission into Neutral, the sputtering usually dies off and goes away. I can also induce it to sputter by turning on the air conditioning, or quickly turning the wheels while stopped, both of which should divert some energy towards the drivebelt components. It will also occasionally stumble if I am on a nice flat piece of road going about 45MPH, at that point the RPM are low and I am hardly pressing the gas pedal, so the engine is probably experiencing similar conditions to stand-still idle.

 

I ran the ECU codes and it returned MAF Sensor, O2 Sensor, Random Misfire, Knock Sensor, and EGR Sensor. The last two were present the last time I had the codes run, but I think that the mechanic didn't reset the ECU. I am hoping that the first three codes were all brought on by one failure.

 

My question then is...Does anyone have an opinion as to the likely culprit? After reading through some posts, this sounds like a problem that might be caused by a faulty MAF sensor. Can I just unplug it and see how it runs, similar to what people have done with the O2 sensor, as a diagnostic? Also, are there two (2) O2 sensors on the Pathfinder, one in each exhaust manifold?

 

Thanks all

-J

Edited May 5, 2005 by jjeffri

[jj big shoe]

Aside from the codes it sounds like it could just be dirty injectors. I'd try a good fuel system cleaner like BG 44K before replacing anything, but then again I'm cheap and lazy.

[k9sar]

the MAF can certainly cause rough idle, bad running, sputtering, etc. Check that your connections are good (if it's idling rough, waggle the wire to the MAF etc). I know there was a pre-96 problem but not sure if they redesigned the connector for 96+

[Mookie]

When my 02 sensor went, it caused problems you are describing under load. More so on the highway against headwinds, uphills, or anytime I'd have to really press down on the accelerator. During city driving, I wouldn't notice anything until the engine got to temp.

 

So, since you are experiencing problems at idle, I'd also start at the MAF sensor. Like K9sar said, on our older Pathys, the ground wire was a common culprit so not sure if that applies to the newer Pathys. If you unplug the MAF, it will run very poorly, so not the best way to judge. Unless of course there is no change when you unplug it. The MAF is out of my area, so I'm sure the others will post up to correct me or to add!

[jjeffri]

Well, I put in a new air filter, the old one was pretty dirty. No luck so far in that fixing the problem. I figured I should try the cheap, easy fix before moving on. Figures it wouldn't work. I will try an look at the MAF later today. I know 88 has done some work on "cleaning" his (maybe using a cotton swab and some sort of solvent), but I am not sure how to do this or what to look for as far as the MAF being damaged.

[Mookie]

How are your plugs and plug wires?

[jjeffri]

Plug wires look OK from the outside. I haven't tested them to see if they are shorting through the insulation, but there are no visible cracks, tears, or rips in the plug wires. The plugs are a little worn, but not awful. I think I could easily justify replacing them, especially at the price, so they are on my list of possible culprits and possible repairs.

[Guest gno]

Hmmmm

[Mookie]

I'm not familiar with the newer Pathy and the way their ECUs work.

Is it possbile to reset and then run the codes again?

 

And yes, I believe yours does have two 02 sensors. Have you tried and unplugged them and go for a spin to see if any noticable changes happen?

[jjeffri]

I have considered resetting simply by pulling the negative terminal from the battery for a while. Then the ECU has to "reprogram" itself. I might do that down the line. I want to try some other diagnostics first.

 

I will probably also get myself a can of Fuel Injector Cleaner (as suggested by JJ Big Shoe) as well, although, I have a suspicion that a bad Fuel Injector would not manifest itself as a MAF code from the Check Engine Light.

 

It seems that the MAF problem that the 95 and under Pathfinders had has been remedied. The MAF plug doesn't contact the underside of the hood. I have tried jiggling the connector but nothing happened. I may need to figure a way to induce it to sputter and then try jiggling.

[jjeffri]

Here is a little update on what I have done to remedy this sputtering problem:

 

I reset the ECU (by unplugging the negative battery terminal for about 45 minutes). This cleared the check engine light and hope all of the codes in there.

 

I next took out the MAF sensor and cleaned with some alcohol and a cotton swab. It had bit of dirt on it, but other than that looked intact. I haven't check the electrical connections to the MAF yet, I need to bring home a multimeter.

 

When I drove the car the check engine light was off. I drove it around for a while and under normal operating conditions, the light didn't turn on. I did notice that when the car is at operating temperature, it idles at about 600 RPM. This seems low to me...at what RPM do most Pathfinders idle? I think it idles around 800 RPM before it is warm.

 

Once I got home I sat in the driveway with the car in drive and my foot on the brake. I turned the steering wheel a couple of times, and low and behold, the check engine light returned. I now need to find out what that code is as well. I am beginning to think that my idle actuator might not be working quite right. I will see what the codes say though.

[jonathanjdfraser]

well jjeffri, i had the same problem with my pathy when i got it, although it wouldnt sputter at 600 rpm, i started the truck and cold, it ran at 2000 rpm, then came down to 1500, and sputtered there, which, clrearly was way to high, so, i cleaned MAF sensor, and it would still sputter, or at at stop light, would have to give it gas because randomly, would drop to like 400 rpm, so anyway, i took off my throttle position sensor, started my truck and then manually gave it gas at the throttle body, without turning the sensor. Then with it still running, i only turned the inside of the sensor (where it make contact with the turning throttle) which made it want to stall. I played around wiht that for a while, and it sems like my sensor is fubar, i've always though that cause at some spots on the trottle, the truck jerks and the engine returns to idle, until i move the trottle again. anyway, i put the trottle postition sensor back on and noticed that where it had been installed, it was titled all the way forward (there are sliders for adjustment) and so i installed it leanin almost centered, even leaning towards the front of the truck a little, started it, and it idles at about 600 warm now, and no sputtering at all, runs great, but i'm still having that common jerking problem, ill be getting a new sensor soon to see if that will help

[jjeffri]

Well, I ordered the Equus Innova 3100 Code Reader (~$100 from Midway Auto Supply). It is not a bad little reader. I easily hooked it up and read the codes and then erased them. The codes that returned where Knock Sensor and EGR Flow problem. I will probably try to get the Check Engine light to return and run the codes again. I don't know why the EGR would cause sputtering and lack of power.