It vapor locks, like, it is just really herky jerky until i floor it and like clean the system out, then it runs fine again. This only happens after I have driven the car for about 30 mins or so, and its warm, then let it sit for half and hour and need to go again, THEN it does the vapor lock like thing. It sucks, and its really weird. Its just started happening, Im thinking either clogged fuel filter (getting to it this weekend coming up), or a clogged injector, now if its the injector, what would I do to fix that???

Thanks for the info/help!

 

1) "Vapor lock" is a condition associated with carburated induction systems, so we know it's not that, as your 4th Gen Max is fuel-injected.

2) What you're describing could be symptoms of problems with any number of related systems. My gut says it's either a fuel, spark, or sensor issue. Could be a coolant temperature sensor, knock sensor, fouled plugs, bad ignition coils, bad plug wires, clogged fuel filter, failing fuel pump. . .

See what I mean? To do a true diagnosis, pick up a Hayne's manual and a digital multimeter (if you don't already have one) and follow the step-by-step diagnostic procedures. It will take some time and patience, but could save you a costly trip to the shop.


Btw, you can help yourself out a lot by stating the model year, mileage and maintenance history of your car when asking a question like this.

 

Yeah, I forgot that part.....its a 95 GXE, 92k.....oil changed every 3k, but havent done my 90k tuneup yet, although the plugs were put in at 75k. All mateinence is normal on the car BUT the 90k so far, Im getting around to it but as of right now that isnt the most important thing I need to be doing (ie school/family stuff = more important).

Just wondering if this isnt something I cant fix easily though...oh yeah my gas mileage is starting to tank it too all of a sudden.

 

bump

 

How long has it been doing it? Could it be a tank of bad gas? Do you always go to the same place for gas?

You could try some fuel injector cleaner, I've always used BG products, 44K. (I think that's the name, someone correct me if that's wrong.)

 

No check engine light on?

I bet it's his Engine Coolant Temp Sensor. Hard warm starts are associated with a bad ECTS. Sometimes they don't throw a CEL because it's working, but not reporting the correct temp of the coolant. In other words, it's out of spec!

After he gets it going, the car clears up because the o2 sensors start adjusting the air/fuel mixture and it runs ok again.

 

Fuel injected engines can easily vapor lock under high temperatures as well. If the problem is aggravated by a fuel pressure issue as well, it could drive you nuts until you fix it.

Granted, modern systems are less susceptible, but the old Bosch L-Jetronic and K-Jetronic systems had some start issues in high temperature applications.

 

Vapor lock is virtually unheard of in modern fuel-injected cars.

See:

http://www.misterfixit.com/vaprlock.htm


Early fuel injection vehicles, where the fuel pump was "suction based" and located in the engine bay, (not in the fuel tank, as all are today) where the fuel inside was prone to heating, and which did not have a fuel-return line to the tank to cool the fuel in the lines could be subject to vapor lock in hot operating conditions. However, this simply doesn't happen anymore with current designs.

Fuel pumps are now located in the gas tank & therefore are not subject to engine heat, which could cause boiling of the fuel in the lines or pump. They "push" cool fuel to the front of the car and have a return line through which excess fuel is returned to the fuel tank. The higher flow rate caused by the excess fuel serves to cool the rest of the fuel in the line, greatly reducing the likelihood of a vapor lock condition.

If you have a fuel pressure problem in a 4th Gen Maxima, this could potentially cause a vapor lock condition, but I'd say unless your fuel pump is bad or you have a severely clogged fuel filter, your 4th Gen Max will never vapor lock.

 

It hasnt been doing it for that long really, maybe a couple weeks? I dont think its a bad tank of gas but we will see, as Im not getting it from where I did just to see, but it has done it once since then.

I guess it couldnt hurt to run some BG 44k thru it, its been a while since I have.

No CEL, no codes showing either. Im sure Ill figure it sooner or later, just thru trial and error....lol

 

I see where you're coming from, but like you mentioned, the cold fuel has to get from the pump to the engine compartment. If the fuel filter is clogged or the system is loosing pressure after shutdown due to bad check valves, the fuel in the lines in the engine bay and the fuel rail itself can start to boil off, leading to a vapor lock issue until the cooler fuel reaches those spots.

Edit: I just realized we're look at this from to seperate viewpoints I think you're talking about a modern fuel injected engine vaporlocking while running. I totally agree with you, a Maxima should not do this. I was looking at it from the standpoint that the engine is vaporlocking after he tries to start it under the conditions he listed. While it's running rough, flooring the gas should help force the cooler fuel past the "locked" point in the system and the problem is gone.

Jr'sMaximaWhen does this issue occur for you? Is it immediately after startup or does it happen later?

 

Immediatly after start up, then when I floor it all is fine again.....only when the car is warm though, when its cold its normal.

 

Okay, I stand behind my original post then. Since it only does it when warm, when the conditions for heat soak are most prevalent, I would say you are having a vapor lock issue. It could be related to the fuel filter itself, or a check valve that is causing the fuel in the fuel rail to flow backwards past it. I'm not sure exactly where those valves are located, but someone with a FSM should be able to help you.

The other possibility, previously mentioned, is the engine coolant temp sensor. If the sensor is bad, the car will think it is cold during every start and meter fuel accordingly. The problem on a warm engine is that this cause way too much fuel to be added and the engine runs like crap. When you move the gas pedal, you're also allowing more air to enter into the equation and the problem clears up.

 

IC - that makes sense to me.

I'm outta steam - I think fundamentally, we agree more than disagree. . .

Cheers,
-K-

 

We're in Colorado, and the temps aren't near warm enough for vapor locking to be an issue. The only time I have witnessed a car vapor lock was in the middle of summer when it's well over 90 degrees outside.

Maybe the temperature isn't that big of an issue but I always thought that was the biggest part of the vapor locking problem...

 

I dont know, Ill get the fuel filter in tomorrow, and BG on my next tank of gas.

I kinda need to find out though what is up since Im gonna be getting a new car soon.........most likely a 5spd max

 

Just check the basics...start with the fuel filter. If thats not it, check the ECTS, the plugs. Do a CEL diagnose. Even if there is no CEL, sometimes it will give you a code (for instance, i have the 0707 code right now, but no CEL).

Let us know how it goes.

~Wes

 

See:

http://www.vbxmaxima.8m.com/fuelfilter.html


This how 2 page is decent, but incorrectly identifies the fuel pump fuse as a 15-amp. For the 4th Gen Maxima's, it's actually a blue 20-amp fuse.

Consult the diagram on the inside of the fuse panel cover for location of the correct fuse.