Pathfinder Acting Up Distributor, Maf, or Fuel Pump?

[PATHFINDER99NI]

Hey all, hope everyone is having a great day.

We'll my '99 LE w/255k is acting up. Ive replaced the dist, and FP with Orielly parts. They seem to have been working well so far, with exception to the FP that seemed to run out of gas around the 1/4 mark, yet only fills up with 12g of gas. Anyway, heres whats going on.

Ive noticed in the last few weeks that the idle seems miss every once in a while, just at idle. Then I noticed that when I floored from a stop or at speed, the engine would accelerate but the truck really wouldnt. I was thinking the transmission was slipping, but its seems more like the transmission isn't getting the request to shift. Being an automatic, transmission takes its cues from all sorts of sensors, so I dont know where to check first.

Can you guys help me figure out what is going bad, where? Im going on a day trip next Friday and I was hoping the pathfinder would be up to the task.

Thanks all

[A1218]

How about your TPS sensor? That has a lot to do with the transmission and throttle input.

When the maf sensor went out on my '97 the vehicle would surge abruptly like if you got rear ended and then stall at idle. I also changed my TPS, bought a Hitachi one online for about $60. The original wasn't causing any problems really but I decided to check it one day when cleaning throttle body and something was rattling inside of it so I just changed it instead of running into problems one day.

Do you have any codes? Sometimes aftermarket distributors don't always work well.

[mdmellott]

Then I noticed that when I floored from a stop or at speed, the engine would accelerate but the truck really wouldnt. I was thinking the transmission was slipping,

In order to rule out transmission slippage, perform a stall test. (see procedure starting on page AT-55 of the factory service manual) >>> https://www.nicoclub.com/service-manual ... 9%2Fat.pdf

[PATHFINDER99NI]

How about your TPS sensor? That has a lot to do with the transmission and throttle input.

When the maf sensor went out on my '97 the vehicle would surge abruptly like if you got rear ended and then stall at idle. I also changed my TPS, bought a Hitachi one online for about $60. The original wasn't causing any problems really but I decided to check it one day when cleaning throttle body and something was rattling inside of it so I just changed it instead of running into problems one day.

Do you have any codes? Sometimes aftermarket distributors don't always work well.

Good point, I’ll check the TPS.

I haven’t scanned it yet, but I’ll do that tomorrow and post what I find.

Thanks!

[PATHFINDER99NI]

Then I noticed that when I floored from a stop or at speed, the engine would accelerate but the truck really wouldnt. I was thinking the transmission was slipping,

In order to rule out transmission slippage, perform a stall test. (see procedure starting on page AT-55 of the factory service manual) >>> https://www.nicoclub.com/service-manual ... 9%2Fat.pdf

I shall do that, thank you very much!

[PATHFINDER99NI]

Alright, well I scanned the truck and saw a “Pending” cam or crank sensor code. Unfortunately I was so quick to clear it, that I didn’t save it to get the code. One of those is in the distributor, right? I’ll scan again and see if the code pops up again. I floored the truck at speed and the same problem was there, just not as bad.

[mdmellott]

One of those is in the distributor, right?

Yep. Your camshaft position sensor is an integral part of the distributor. If it's bad, the entire distributor has to be replaced. Your crankshaft position sensor is mounted at the rear of the engine, on the transmission bellhousing.

[PATHFINDER99NI]

I should mention that while I was scanning the PCM, I tested the TPS by flooring the throttle (engine off) and it only went to 86% when it should have been at 100%. How can I reset the TPS, or does this mean the TPS is shot?

[mdmellott]

I should mention that while I was scanning the PCM, I tested the TPS by flooring the throttle (engine off) and it only went to 86% when it should have been at 100%. How can I reset the TPS, or does this mean the TPS is shot?

No worries. A TPS will never read 100% at WOT. For your '99, approximately 80% at fully opened is good. (see page EC-151 of the factory service manual) >>> https://www.nicoclub.com/service-manual ... 9%2Fec.pdf

Get familiar with this engine controls section of the FSM. There are several mechanical adjustments your ride needs to have accurately set for everything to work well together. Aside from TPS adjustment, there is your fast idle cam, idle speed, ignition timing, and idle mixture ratio adjustments to consider. All of these can be properly checked and adjusted following the steps outlined in the basic service procedures chapter of this section of the FSM. Since there are so many manual adjustments required to be correct for proper inputs to the PCM for it to correctly make its automatic operational calls for injector fuel delivery, these human inputs first need to be accurate. Since the O2 sensors depend on this fuel delivery to be righteous as well, your fuel consumption efficiency will suffer if the manual adjustments are out of spec.

Knowing what does what, when, and how will help you avoid spending time and dollars on things not needed. The FSM is great for specification details and what to do but sometimes comes up short on how to do it. I like using the Haynes Repair Manual as a good how to book for getting many things done on my Pathfinder. https://www.amazon.com/Pickups-2000-200 ... 1563923963
It's available used for less than $3 at Amazon. Even new at $30, it will pay for itself in the time and money it can save you.

[PATHFINDER99NI]

Well it turned out that my distributor was bad. I kept getting a P0340 code. Luckily my distributor was under warranty, so I was able to get a new unit.

Thanks for all the help!