Troubleshooting what I think is limp mode

[Bigcountry]

I have a 94 Nissan Pathfinder xe-v6, 5 speed 4x4, it has no error codes, it flashes 55, the truck cranks and ideles great when you try to accelerate at about 21 to 2200 rpms the vehicle stalls and does not recover until it gets to 1000 rpm's it feels like someone turns off the ignition switch,

it does not matter what gear I'm in or in neutral, I can drive it I have to baby it and top speed is around 45 miles per hour! While trying to troubleshoot I unplug the TPS sincer and to my surprise it runs like a bat out of hell but the check engine light comes on and throws a GPS which code and also it idols rough and will not pass inspection , and the gas mileage gets even worse which if you have one you already know the gas mileage is not very good, I have changed quite a few parts sensors and switches to try to fix this problem

can you any one help please

[Terranovation]

Sounds fuel filter related it might be contaminated. Also check air filter, engine can't breathe properly if that's clogged. If it's automatic, change the fluid. Mine behaves the same way, if it's hunting gears usually a fluid drain and refill fixes the problem because after a while atf loses it's viscosity and makes it hard for the gear syncros to change gear. I change mine every 10,000 km (16,000 miles) some say that's overkill but I've done over 100,000 miles on this trans and it's going great so I must be doing something right.

[Bigcountry]

I don't think you quite understand what I'm talking about but its understandable it whatever gets there and then turn and turned it back on when it gets 1100rpm thank god it's 5speed so I can just push the clutch I think it's going to take a pro to tell me what to do

[Slartibartfast]

Interesting that unplugging the TPS got it running (sort of) better. The TPS is what tells the computer when it's supposed to make the engine idle, so if that's broken, it could be telling the ECU to idle all the time. You get on the gas, the engine revs way above what it should do at idle, and the ECU panics and cuts spark or injector pulse to bring it back down.

With the sensor unplugged, the computer doesn't know when the engine's supposed to idle, so it's not adjusting the idle air control valve or doing any of what it's supposed to do there, which would explain the rough idle. I don't know for sure but I suspect its response would be to throw more fuel at the problem, which would explain why your mileage got worse.

I would start with the TPS. Keep in mind that there's a little adjustment to it as well; if you or someone else had it off just before the problem started, it might just need adjustment. I haven't messed with mine but the service manual (here, download the '94 or '95 manual and look in the EF&EC section) should walk you through it. I would probably just hook a multimeter to the closed throttle position switch and adjust it so the points close when the throttle's shut.

[Bigcountry]

It's not the switch is just sensor it has two plugs and it's the one that has the wires attached and not directly to the sincer, but I did replace the TPS switch just in case, also replace the o2 sensor and the knock sensor

Edited February 21, 2016 by Bigcountry

[Slartibartfast]

And replacing it didn't change anything?

[Bigcountry]

No did not change anything

[Bigcountry]

I am so frustrated and confused by the fact! Have not found anyone else that even knows anything about it or anything like it

[hawairish]

Shot in the dark here, but how did you pull the 55 code? With a scanner or the ECU screw? If the latter, is it possible it was left in one of the diagnostic modes?

 

Have you checked any of the other diagnostic modes results per the FSM?

http://www.nicoclub.com/FSM/Pathfinder/1994_Pathfinder/ec.pdf

[RCWD21]

Here's a thought since this sounds very similar to what happened with my 95 hardbody, is it possible you've gotten bad gas or water in your tank?

 

I got some gas at Walmart because I couldn't make it to a better station, I only got a couple gallons worth and thanks to the high ethanol content it attracted moisture like crazy and I had the very same symptoms as you described earlier.

 

It would run and idle fine but wouldn't rev correctly and if you gave it too much gas it would fall flat on its face until the rpm got real low and picked back up again.