Jump to content
SAU Community

Recommended Posts

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

Link to comment
https://www.sau.com.au/forums/topic/379231-pfc-dj-off-throttle-issue/
Share on other sites

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 by Don Dada

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 by snozzle

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 ;)

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.

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 by JonnoHR31

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.

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 :spank:

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.

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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • For once a good news  It needed to be adjusted by that one nut and it is ok  At least something was easy But thank you very much for help. But a small issue is now(gearbox) that when the car is stationary you can hear "clinking" from gearbox so some of the bearing is 100% not that happy... It goes away once you push clutch so it is 100% gearbox. Just if you know...what that bearing could be? It sounding like "spun bearing" but it is louder.
    • Yeah, that's fine**. But the numbers you came up with are just wrong. Try it for yourself. Put in any voltage from the possible range and see what result you get. You get nonsense. ** When I say "fine", I mean, it's still shit. The very simple linear formula (slope & intercept) is shit for a sensor with a non-linear response. This is the curve, from your data above. Look at the CURVE! It's only really linear between about 30 and 90 °C. And if you used only that range to define a curve, it would be great. But you would go more and more wrong as you went to higher temps. And that is why the slope & intercept found when you use 50 and 150 as the end points is so bad halfway between those points. The real curve is a long way below the linear curve which just zips straight between the end points, like this one. You could probably use the same slope and a lower intercept, to move that straight line down, and spread the error out. But you would 5-10°C off in a lot of places. You'd need to say what temperature range you really wanted to be most right - say, 100 to 130, and plop the line closest to teh real curve in that region, which would make it quite wrong down at the lower temperatures. Let me just say that HPTuners are not being realistic in only allowing for a simple linear curve. 
    • I feel I should re-iterate. The above picture is the only option available in the software and the blurb from HP Tuners I quoted earlier is the only way to add data to it and that's the description they offer as to how to figure it out. The only fields available is the blank box after (Input/ ) and the box right before = Output. Those are the only numbers that can be entered.
    • No, your formula is arse backwards. Mine is totally different to yours, and is the one I said was bang on at 50 and 150. I'll put your data into Excel (actually it already is, chart it and fit a linear fit to it, aiming to make it evenly wrong across the whole span. But not now. Other things to do first.
    • God damnit. The only option I actually have in the software is the one that is screenshotted. I am glad that I at least got it right... for those two points. Would it actually change anything if I chose/used 80C and 120C as the two points instead? My brain wants to imagine the formula put into HPtuners would be the same equation, otherwise none of this makes sense to me, unless: 1) The formula you put into VCM Scanner/HPTuners is always linear 2) The two points/input pairs are only arbitrary to choose (as the documentation implies) IF the actual scaling of the sensor is linear. then 3) If the scaling is not linear, the two points you choose matter a great deal, because the formula will draw a line between those two points only.
×
×
  • Create New...