1KZTE Rough idle / engine occasionally

[Black94Prado]

Hey so occasionally I get a rough idle or inconsistent power. Would this typically be a fuel injector or fuel pump issue?

 

[Zorlac]

How the engine works when you give it a cold start

the issue happens when the motor temperature is in the normal range?

 

[Waikato Willy]

hey I get the same, like it sounds like its going to cut out after idling for 10 mins or more and weird intermittent loss of power of the throttle when slightly pressed, kinda of like a surging, really hard to diagnose but Ive lived with it for a year as it comes and goes and it doesnt bother me to much, when flat out its fine, I was thinking the TPS but still not sure and it doesnt really affect general driveability

 

[Black94Prado]

How the engine works when you give it a cold start

the issue happens when the motor temperature is in the normal range?

Yeah issue happens when the motor temp is normal. Happens occasionally during cold starts and regular engine starts but not any more often then when driving or stopped at a red light. It'll even cold start fine and then randomly have one of these bouts of rough idling/power loss once warm. Waikato, sounds exactly like what I'm experiencing.

 

[oldblue]

My Prado does this but when it misses it puts out a little puff of smoke expressly on a slight down hill run. Thought it may be to do with blocking of the exhaust EGR.

 

[Waikato Willy]

yep its really random, and really noticeable when idling for ages(its helps to keep my 7month old baby asleep) so it will be idling for a good 2hrs sometimes and this drop in revs and stutter comes in goes everysay 10-15mins, its like its about to run out of diesel then idles back up, Aircon does not affect this even though the revs are a bit higher when the pump engages
also really noticeable in 3rd on the auto when just lightly feathering the throttle, I can actually make it do the surging by just touching the throttle pedal, somedays its mint, then all of a sudden it will do this randomly, I might dig into it a bit more, I just thought it might be all the mucking around I do with the wiring, more boost,no egr and exhaust?

 

[Beau]

When last have you changed the fuel filter? Also the IP itself has filters within that could probably do with a clean. You can also put a temporary clear return line from the pump and see if there are any air bubbles in the system. Don't know how many miles you have on the truck but I got 250,000 miles out of my injectors before swapping them out. Have you ever had the intake off and are you still running a EGR? If so, get that sucker blocked off, and clean the intake manifold as it's most likely very caked!

 

[Waikato Willy]

i do fuel filter every 10,000, its actually off a nissan patrol,its got a good diaphragm pump and bleed on it
spill valve filters all cleaned not long ago as well
I have a permanent clear line running from the filter housing to the top of the pump - no obvious signs of air bubbles
Intake manifold has been cleaned in acid and no EGR left

It does point to air leaks in the diesel system though ,I was running a facet lift pump and even when this was running all the time it still suffered the issue, might try another lift pump like a holley blue ive got lying around to see if it changes the symptoms

 

[gotoy]

..also check the ECU electronic components inside. Leaking capacitors and dry joints, have them replaced or re-soldered.

 

[Beau]

Check for any wetness around the injectors too.

 

[GTSSportCoupe]

..also check the ECU electronic components inside. Leaking capacitors and dry joints, have them replaced or re-soldered.

Yes, do this ^^. These ECU's all seem to have failing capacitors in the KZJ71/KZJ78 trucks. The leaking dielectric etches away copper on the circuit board and can cause all sorts of problems.

Looks like this (black stuff on circuit board):