Can anyone help with these symptoms?

[rjorgens]

Hi,

I just joined here because my normally reliable 1994 Pathfinder SE has started acting out. She has 220K miles and always runs great, until now. Here we go:

 

About a month or so ago, I noticed a strong smell of unburned gas when I started her up. Then I noticed my gas mileage was getting bad. It's been getting worse. A couple weeks ago I saw what I thought was gas dripping out the tailpipe when idling, the smell was bad. So I checked my oil and it was black, and more full than I thought it should be. I changed the oil (it smelled like gas to me, too), and then I checked the ECU for codes, all I have was "55". No check engine light. At this point the car was still running fine.

 

Then I noticed that my transmission was shifting at a higher rev, and harder, like I had pushed the "power" switch. I double checked that it was set to "auto".

 

Since I have no code, I don't really know where to start. And just a couple days ago, she started trying to stall when I brake to a stop (IAC valve?). This only happens when its hot outside.

 

I have parked her because I'm afraid that gas is diluting the oil and I might burn a ring.

 

So, stuck injector? Bad fuel pressure regulator? Bad O2 sensor? Bad Idle air control vale? Why would any of this affect the tranny shift point? Does the computer have me in an open loop mode?

 

I need this car for commuting to work. I've made an appointment with a mechanic I can trust, but if I could fix it myself I would love to, money is tight.

 

Any thoughts, ideas, would be appreciated. Thanks!

[adamzan]

Could be the o2, or a plugged up cat. Those are 2 things I can think of that I had go wrong on mine. The reason the tranny is shifting higher is because the truck is having to go to higher rev's to build up speed, at least higher than normal.

[nismothunder]

Mine was try to stall when I hit the brakes too,I'm not sure why but it did go away...

[silverton]

Does it feel like it's lost some power? if so, I would also vote a plugged up cat. Which usually a plugged cat and a bad o2 sensor go hand in hand. so check both of them.

[rjorgens]

I don't know, she seems pretty peppy still. I just had a whole new exhaust system put on about 20K ago, with

a high flow aftermarket cat.... I doubt its that - but I am suspecting the O2 sensor, I've heard it can be bad and not throw a code.

 

 

Does it feel like it's lost some power? if so, I would also vote a plugged up cat. Which usually a plugged cat and a bad o2 sensor go hand in hand. so check both of them.

[Precise1]

Clean the MAF (can't hurt, procedure in the Garage How To section) and check the resistance of the O2 sensor. Should be 1-1000 ohms IIRC (values listed in a pinned thread in the Garage section) and also go into the Garage section and download the FSM for your year (pinned at the top) there may be additional steps in it. You could also have a stuck or leaky injector, but that should throw a code so lets start with the basics first.

 

B

[rjorgens]

OK, I can clean the MAF, and I'll check the o2 resistance. (I'm an EE). I'm going to postpone my mechanic visit and see if you guys acn lead me through to a fix.

 

How do I check for a leaking/stuck injector?

 

How do I check for a plugged CAT?

 

R

 

 

Clean the MAF (can't hurt, procedure in the Garage How To section) and check the resistance of the O2 sensor. Should be 1-1000 ohms IIRC (values listed in a pinned thread in the Garage section) and also go into the Garage section and download the FSM for your year (pinned at the top) there may be additional steps in it. You could also have a stuck or leaky injector, but that should throw a code so lets start with the basics first.

 

B

[JamesRich]

You can check for a plugged cat with a vacuum gauge, but you would have lost power if the cat was plugged. It does sound like you have low vacuum if the tranny is taking longer to shift though. Also pull the vacuum hose off of the fuel pressure regulator while its running and look for fuel in the vacuum port. I've seen this problem on a few older Nissan's. The diaphragm starts leaking and lets fuel into the vacuum side. On a 85 300z the fuel was actually dripping out of the exhaust.

James

[rjorgens]

Alright - follow up -

 

I ordered a fuel pressure regulator and O2 sensor from Rock Auto. Couldn't find the fuel pressure regulator at first. Had to get the shop manual out, found a picture of where it was (after searching for 15 minutes). Put my hand down there in the back of the engine behind the intake manifold and viola! There was no vacuum line hooked to the back of the intake manifold. I dug around and found it. The end that hooked to the manifold was a little hard, and cracked. I cut it off an re-attached it.

 

How did that come off? I don't know - maybe when I was trying to replace that horrible back spark plug a long time ago? Maybe a mouse? (I've had them chew my wires a couple of times).

 

I'm going to drive her and see how she does. Maybe I can get my $150 back from Rock Auto. Goes to show you should check for the obvious first. Thank you everyone. It was the vacuum/fuel pressure regulator (tranny shifting high) comment from James that got me going down the right path. I had no vacuum. Its a wonder it ran so well.

 

Will let you know how she runs.

 

 

 

 

 

You can check for a plugged cat with a vacuum gauge, but you would have lost power if the cat was plugged. It does sound like you have low vacuum if the tranny is taking longer to shift though. Also pull the vacuum hose off of the fuel pressure regulator while its running and look for fuel in the vacuum port. I've seen this problem on a few older Nissan's. The diaphragm starts leaking and lets fuel into the vacuum side. On a 85 300z the fuel was actually dripping out of the exhaust.

James

[Kingman]

You can check for a plugged cat with a vacuum gauge, but you would have lost power if the cat was plugged. It does sound like you have low vacuum if the tranny is taking longer to shift though. Also pull the vacuum hose off of the fuel pressure regulator while its running and look for fuel in the vacuum port. I've seen this problem on a few older Nissan's. The diaphragm starts leaking and lets fuel into the vacuum side. On a 85 300z the fuel was actually dripping out of the exhaust.

James

 

No RE4 transmission uses vacuum for shifting, it's all done electronically with the various engine sensors and pre-set guidelines from the TCU.

[rjorgens]

Ah, but having no vacuum could throw all those engine sensors into confusion? We'll see - haven't done the test drive yet. May be separate problems..

 

 

 

No RE4 transmission uses vacuum for shifting, it's all done electronically with the various engine sensors and pre-set guidelines from the TCU.

[Kingman]

Very possible. If the engine isn't running right, sensors change parameters and give wrong readings that can mess with stuff. A few examples: when my '93 Explorer had a bad fuel pump relay the transmission would shift hard and really high. My '88 Suburban had a cracked distributor cap and would randomly misfire and when that happened the transmission would barely shift at al. When the problems on both vehicles were fixed, everything was silky smooth again.

[JamesRich]

No RE4 transmission uses vacuum for shifting, it's all done electronically with the various engine sensors and pre-set guidelines from the TCU.

 

Yes I know that but when the vacuum is low the MAP sensor tells the ECM that the engine is under a heavy load and should let the trans stay in a lower gear to help out. At least that is how it works on American made vehicles. I haven’t done any computer work on any Nissans because there computers system hardly ever have problems.

James

[rjorgens]

So after re-attaching the vacuum line from the fuel pressure regulator to the intake manifold, everything seems to be back to normal again. She's running much nicer, no decelerating stumble, gas smell is gone except right at cold startup, transmission shifting normally again.

 

I changed the oil again because it was already black, with a gas smell.

 

I think I've done it. I'll keep my new parts until I check the O2 sensor to make sure its OK.

 

Thank you everyone for you support!

 

[silverton]

Glad you got it figured out and it was something really simple! Would have been horrible to just keep throwing parts at it...

[Specv1973]

I'm glad I saw this thread......my hose was split and fell off my pressure regulator too.....everyone should be checking this dumb little hose......my vacuum hose diagram is on the hood still....so it was easy to just check the rest of them......and the third to overdrive shift was taking forever before.....now it's not anymore. I didn't have any gas fumes or drive ability problems though like this guy did. Weird......I also found the thread on the MAF cleaning procedure and went ahead and did that too just for the heck of it........the only thing I picked up so far is quicker shifting in Auto mode. (I don't use the Power mode unless I tow, which does make for longer shifts as it's supposed to.)

[rjorgens]

I'm really glad that reporting my problem, asking for help, and following up with what I found helped someone else.

 

Reply here if you want to hear my story about the passenger side rug getting wet after a rain, and the really weird solution I found....that one took me a year to figure out.

 

Also, I would be interested in hearing more about how to mount 6x9 speakers in this rig. The 4x6s I found to replace the fronts, and the 5 1/4" I have mounted in the back roof (even though they are Boston Acoustics) just aren't cutting it for me. I have a set of BA 6x9's I'm dying to put in here....

 

Thanks!

[Specv1973]

I would like to hear about the wet rug solution.....I don't have it yet....but you never know.....these vehicles ain't gettin any younger.

[Precise1]

I'm really glad that reporting my problem, asking for help, and following up with what I found helped someone else.

 

And that is what it is all about...

 

B

[shooter]

I'm really glad that reporting my problem, asking for help, and following up with what I found helped someone else.

 

Reply here if you want to hear my story about the passenger side rug getting wet after a rain, and the really weird solution I found....that one took me a year to figure out.

 

Also, I would be interested in hearing more about how to mount 6x9 speakers in this rig. The 4x6s I found to replace the fronts, and the 5 1/4" I have mounted in the back roof (even though they are Boston Acoustics) just aren't cutting it for me. I have a set of BA 6x9's I'm dying to put in here....

 

I will take a guess on the wet rug problem. Fresh air intake on the back of the hood plugged up with gunk and won't let rainwater drain out so it overflows into cab?

[rjorgens]

I'm really glad that reporting my problem, asking for help, and following up with what I found helped someone else.

 

Reply here if you want to hear my story about the passenger side rug getting wet after a rain, and the really weird solution I found....that one took me a year to figure out.

 

Also, I would be interested in hearing more about how to mount 6x9 speakers in this rig. The 4x6s I found to replace the fronts, and the 5 1/4" I have mounted in the back roof (even though they are Boston Acoustics) just aren't cutting it for me. I have a set of BA 6x9's I'm dying to put in here....

 

I will take a guess on the wet rug problem. Fresh air intake on the back of the hood plugged up with gunk and won't let rainwater drain out so it overflows into cab?

 

 

 

 

 

No. There is a clear plastic drain tube that comes down from the sunroof. As far as I can tell it's supposed to drain into the fender. But mine was routed through the kick panel, and under a big bundle of wires. This never caused a problem until the car got old enough so the sunroof gaskets didn't completely seal. Then, after a big rain, I would have a wet passenger side rug. I looked cleaned and sealed EVERYTHING I could think of - still leaked.

 

Finally found it after about a year of looking. I had taken out the carpet and kick panel - I could see the water was coming from there in the corner, under a big bundle of wires. So I thought it was coming down the wire bundle and sealed that up where it came through the firewall (but couldn't figure out how water got there with the hood closed). I waited until the next BIG rain storm (get them often in Seattle). I climbed in down on the floor and just watched. After a while here comes a trickle of water - dang! (not what I said). I was so frustrated I pulled the big bundle up from the floor - and there it was , a little clear tube coming out of the kick panel (from inside the fender) - and water coming out of it.

 

I finally tracked down where the tube came from - up the windshield pillar -

 

I think it was just mis-routed in the factory, it should have just been emptying in the fender...also it is just back up and doesn't drain water if the sunroof seals well....

 

Mystery solved.