Pfc Dj Off-Throttle Issue

[snozzle]

Hey all,

Yesterday my car developed a rather strange issue whilst i was driving, i noticed that on deceleration in any gear id hear a pop in the exhaust every a few seconds. At the same time that this pop is occuring im seeing the inj duty rise from 0% to 3% for a split second.

Thought it might be my TPS, checked the voltages and its sitting on 0.38v the whole time and before i completely ruled out the TPS i replaced it with another one and the issue was still there.

Another problem started shortly after that where I would stop at the traffic lights and my idle would drop to 500rpm or so then rise to 1000rpm again and then cycle through this about 2-3 times before it would finally stabilise and idle properly.

The car drives fine when the throttle is open, still makes great power and my ignition has no issues whilst on boost, the only issues are when the throttles are closed the ECU seems to be on cocaine?

Not sure if this will help but the idle stabilisation issue starts to go away after 15minutes of driving,

Car is going to my tuner tomorrow to see what he can sus out but I thought id gather somo info of my own to save my tuner from wasting his time as hes quite busy!

Anyone got any idea what the cause of this is ? I hope its not my ECU spitting the dummy on me !!!

Thanks

oz

[mico]

mine pops when cold, i got the same gear as u. are u runnin oxy sensors ? or maybe 3 and 4 runner are gettin different air flow when tb is shut ??

[snozzle]

Not running oxygen sensors, was tuned without them.

As i said the issue started today, before today it was fine so Im sure theres some gremlin somewhere im just stumped as to where to look..

[JonnoHR31]

long shot but does the coolant temp sender output change at all?

[snozzle]

Nope, stays on 80degress

[Don Dada]

Two things I can think of would be either tps or map sensors

Did you have a look at the map sensor voltages when it does it?

I get that same problem (L jetro) when on decel and only if I gently rest my foot on the X, It starts to pop and gurgle and ign goes way retard like 5-10*

If I dont touch the X, ign remains on 20* and no pops or farts

^Btw. Is that normal?

Edited October 5, 2011 by Don Dada

[snozzle]

Already ruled out the TPS,

Map sensor voltages are consistent with eachother but im not sure if they would be causing it as car drives fine on boost?

I havent looked at what the ignition timing is doing when the popping happens but even if it is retarding, what does that imply?

Yeah whenever i touch the accelerator it does that popping like you said but it never did it if my foot was off the accelerator, but now its doing it when my foot is off which is why im concerned

While the popping is occuring the TPS is 0.38-0.40v and it isnt moving about which would explain the popping.. but its not

Edited October 5, 2011 by snozzle

[Room42]

Deccel fuel cut?

[89CAL]

Two things I can think of would be either tps or map sensors

Did you have a look at the map sensor voltages when it does it?

I get that same problem (L jetro) when on decel and only if I gently rest my foot on the X, It starts to pop and gurgle and ign goes way retard like 5-10*

If I dont touch the X, ign remains on 20* and no pops or farts

^Btw. Is that normal?

X = Accelerator? Then yes

I get no fuel at all on normal decel, but if I hold my foot lightly on the accelerator it will see AFR's around 13:1 from memory

Just the way it is. Best to leave your foot off the accelerator when slowing down

[R31Nismoid]

It's injector related. There is a RPM setting, ill find out what it was next week if someone doesnt post up sooner.

I had the same issue with my car, was popping & backfiring, on occasion throwing massive flames too. Was also "jerky" with inj duty going from 0-4% like a wave.

Adjusted a RPM setting (NFI what menu) to around 3400rpm (so it wouldnt do it below 120km/h in 5th) and never had a problem since. Can tap/rest on the throttle and its perfect.

As the car is throwing in fuel, and then taking it out without any change in load. Hence the carrying on.

[JonnoHR31]

Deccel fuel cut?

yes its not properly fuel cutting, thats the problem

nismoid, did you adjust the fuel cut rpm limit? its the 2 f/c rpm settings in the rev/idle menu, one for aircon off and one for aircon on. whats yours set to snozzle?

Edited October 5, 2011 by JonnoHR31

[R31Nismoid]

Wasn't me - tuner was adjusting it until we found a sweet spot!

Dont think it was that though? I'll see if I can have a look tonight actually, i know it was set to 3400 so it wont be hard to find if i trawl the menus for long enough.

[R31Nismoid]

yes its not properly fuel cutting, thats the problem

nismoid, did you adjust the fuel cut rpm limit? its the 2 f/c rpm settings in the rev/idle menu, one for aircon off and one for aircon on. whats yours set to snozzle?

Took me a while - checked before, can confirm that was it.

1st RPM for me is the launch limiter as i have a PFC Pro

The second one is set to 3100rpm - If I back it off to 1800rpm say... It starts to play up a bit almost immediately

[GTRNUR]

If you tune with FC-Edit start a log session and open the Map watch. Select the Advanced PIM value and filter for Minimum values.

Then give the engine a big rev and let it fall back to idle with the throttle closed. If your PIM value falls below your Settings 3/Map Reference 01 load PIM value, then thats your problem. The ECU is interpolating your top row of fuel values back to Zero, based on the PIM values your MAP sensors are generating.

This issue causes a lean pop or burble on down shifts and partial throttle/no load conditions such as rolling down hills. It also causes a throttle hesitation issue from a closed throttle, as your accelerate injector settings on page 2 reference the current map load point. And if that load point is lean then the engine will hesitate.

There are 2 solutions.

1. would be to make a note of that lowest value, and change the 01 PIM value to be this new low value. Eg: you see 890 as a PIM value, set 01 load PIM load to 800. This will help with situations where you down shift while the throttle is closed and it pulls a really strong vacuum.

2. would be to change the offset values for your MAP sensor, but that also means re-tuning the ignition and fuel maps from scratch.

[snozzle]

Woopsie, I should have updated this! I have actually got the problem fixed.

Turns out the TPS i swapped to was also on its way out as it was a little too sensitive just like my old one.

My tuner set the tps to 0.32v instead of 0.40v and the problem has gone away. Turns out the TPS was spiking above 0.40v quicker than what the power fc commanders refresh rate was so it was injecting fuel in as the ECU was thinking the throttle was opening by a bee's dick every few seconds.

Although the problem is solved, im going to buy a brand new TPS soon though.

Thanks for the input guys.