Hey guys,

I'm having a funky idle-issue. Just drops to sub 500rpm when at a stop-light, then recovers, then drops again. Already replaced IACV, ECU, Sparkplugs, Coils, FPR, Fuel-Damper.
Hopefully its the EGR stuck!? Out of ideas soon lol

Where is the EGR located on the car? Can't seem to find it... has to be on the head or ex-manifold?

thanks

The 3.5L Pathfinders do not have a EGR valve. Do you have a scan tool that can look at real-time data to see what your fuel trim readings are?

mdmellott wrote: ↑

Wed Sep 16, 2020 7:47 pm

The 3.5L Pathfinders do not have a EGR valve. Do you have a scan tool that can look at real-time data to see what your fuel trim readings are?

that's interesting! I see the purge VSV, etc... so no EGR. okay - rules out that being the issue then.

yeah, the trims are going haywire... can't specifically remember but it was way out of range, yes

After you have the engine completely warmed up, tell me what the short term fuel trim (STFT) and long term fuel trim (LTFT) readings are for bank 1 and for bank 2 while the engine is idling. If there is an air intake or a fuel delivery issue going on, the STFT readings may be unstable at first but they should level out to around 0%, give or take a few percent, after the LTFT has learned where it needs to be in order to balance the air/fuel ratio at 14.7:1. To get some idea of what's going on, I would have to know what those fuel trim numbers are for both banks. The numbers are either positive or negative percentages.

mdmellott wrote: ↑

Wed Sep 16, 2020 8:32 pm

After you have the engine completely warmed up, tell me what the short term fuel trim (STFT) and long term fuel trim (LTFT) readings are for bank 1 and for bank 2 while the engine is idling. If there is an air intake or a fuel delivery issue going on, the STFT readings may be unstable at first but they should level out to around 0%, give or take a few percent, after the LTFT has learned where it needs to be in order to balance the air/fuel ratio at 14.7:1. To get some idea of what's going on, I would have to know what those fuel trim numbers are for both banks. The numbers are either positive or negative percentages.

hey, thanks for the quick reply. I'm fairly familiar with fuel/air and trims as I build performance cars haha... the reader is pretty low end so the readings are unstable and flickers.
From what I can remember it was always +15-20%. Also occasionally has a misfire MIL. The only thing not replaced at this point is injectors lol

I forgot: MAF is new as well, O2 sensors were replaced a year or 2 before. This isn't my car, I just help my buddy out since he has no automotive clue whatsoever.

Ok. So that's +15 to 20% LTFT on both banks? That's kind of a high lean condition. Almost enough to trigger a DTC.

mdmellott wrote: ↑

Wed Sep 16, 2020 9:00 pm

Ok. So that's +15 to 20% LTFT on both banks? That's kind of a high lean condition. Almost enough to trigger a DTC.

Late reply...threw in new injectors.

Here is whats going on - like clockwork:
STFT 0%... car drops idle.. STFT goes up to 25% exactly: during the fuel-"dump" it stabilizes idle. Once 25% is reached the idle drops again.
STFT compensates again up to 25% (idle stable) - once 25% reached, drops out.
You can set your watch to it lol

So either a MASSIVE vacuum-leak or not enough fuel.. fuel-filter!?

I'm thinking a vacuum leak would be more consistent and continuous. Fuel delivery on the other hand, caused by a clogged fuel filter or a weak fuel pump could be inconsistently starving the engine. Changing the fuel filter is easy enough to rule that out. Back there under the car by the spare tire where the filter is, just happens to be where you would have to check the fuel pump pressure as well. There is no Schrader valve anywhere in the fuel lines to connect a pressure gauge and no easy access in the engine bay to tap a line with a tee-connector. Putting a tee-connector at the filter is the way to go for connecting a pressure gauge between the filter and the fuel rails. This '02 Pathfinder fuel system pressure should be 43psi with the key On, engine Off. With the engine idling, the pressure should be 34psi.

Matce wrote: ↑

Sat Sep 19, 2020 8:22 pm

mdmellott wrote: ↑

Wed Sep 16, 2020 9:00 pm

Ok. So that's +15 to 20% LTFT on both banks? That's kind of a high lean condition. Almost enough to trigger a DTC.

Late reply...threw in new injectors.

Here is whats going on - like clockwork:
STFT 0%... car drops idle.. STFT goes up to 25% exactly: during the fuel-"dump" it stabilizes idle. Once 25% is reached the idle drops again.
STFT compensates again up to 25% (idle stable) - once 25% reached, drops out.
You can set your watch to it lol

So either a MASSIVE vacuum-leak or not enough fuel.. fuel-filter!?

Hey Matce I'm curious if you ever figured out the issue you were experiencing, or at least a lead on what might have been going on. I've got a 2002 Pathfinder as well and I'm going through something similar, cheers!

cham24, I know we're chatting over an NPORA but Matce's symptoms were exactly what mine was doing. He mentioned new injectors. I had serviced mine and apparently installed slightly smaller o-rings on the nozzle side of 4 injectors, 2 per bank. If you can confirm you've got the same STFT and frequency, could be related? Though, my truck also threw codes P0171 (Fuel Injection System Malfunction; induced by intake air leaks at the plugs) and P0507 (High idle; seemingly induced by excess fuel being metered to counter excess air). New o-rings (the correct ones!) solved my problem.

Haha thanks Hawairish! First time using this platform but when I was researching my issue I found this thread and thought I'd ask. Sounds like replacing injectors did not solve his problem. I'll look into timing the frequency of Fuel trim switching. I can tell you my trim percentage is not going as high as it sounds like yours was. Barely making 10% at idle and its rare.

The only real difference is my RPM doesn't quite drop to below 500 in gear but there is some type of drop then recovery every 5 seconds or thereabouts. In total only really a variance of about 50-75 RPM though when dropping and recovering. I'd like to avoid touching my injectors and fuel rails when I swap my valve covers as I've seen it be a right chore trying to keep all the parts together etc. Smoke test should reveal if there is a leak in that general area though with the plenum on I won't be able to tell right away if its my injector o-rings or not.