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SOLVED Strange Idle RB25


JOEL
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Hey Everyone,

Wondering if anyone can help me out with this idle issue I have,
Idle jumps up and down and cant seem to figure out why.

For example while idling, the AFR is very lean for some reason. AFR Guage in car shows it jumps between 22 and 16ish sometimes between 22 and 29 when at operating temp. When cold sometimes its between 9 and 15, so a very large range.
I've tried adjusting the fuel table to try make it idle at a normal AFR but values look way to high (idle values higher than WOT values).

So I've left it how it was, just wondering if anyone can look at my map and log to see if there is anything strange they can see.

 

Thanks

130122 weird idle.pclx weird idle.llgx

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Some thoughts...

AFR too lean. Why do you have Master Fuel -35%?

Turn on ISC Idle Ignition Control
MAP lockout - put a little bit higher value as your idle MAP touches up on it.
Integral Gain - you may need to set this a little bit lower to minimize oscillation
Min Clamp - your value is too low
Idle Base Position table - values too low for target idle

So, you need to follow the open loop idle speed control procedure in the help file. If you've gotten the idle close to target, by then you can change to closed loop idle speed control. 

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Appears to be a misfire or fuel related issue to me.  Does it run smoother if you richen it up so the lambda is richer than stoich?  Is your wideband definitely an X series, not the older one?  Do you get a similar RPM drop if you disconnect one injector at a time?

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11 hours ago, essb00 said:

Some thoughts...

AFR too lean. Why do you have Master Fuel -35%?

Turn on ISC Idle Ignition Control
MAP lockout - put a little bit higher value as your idle MAP touches up on it.
Integral Gain - you may need to set this a little bit lower to minimize oscillation
Min Clamp - your value is too low
Idle Base Position table - values too low for target idle

So, you need to follow the open loop idle speed control procedure in the help file. If you've gotten the idle close to target, by then you can change to closed loop idle speed control. 

3 hours ago, Vaughan said:

Does it sound like it's missing at idle? A miss will present as being lean due to the unburnt oxygen

3 hours ago, Adamw said:

Appears to be a misfire or fuel related issue to me.  Does it run smoother if you richen it up so the lambda is richer than stoich?  Is your wideband definitely an X series, not the older one?  Do you get a similar RPM drop if you disconnect one injector at a time?

 

Thanks for your responses,

essb00 I've tried your suggestions but this made the car worse, my master fuel is set at -35% as my afr when driving shows that number is best, around 11.5 stoich at WOT.

Vaughan and Adamw, The car does seem like it has a slight misfire on idle due to the leanness.
When I richen it above stoich, the idle still jumps up for 5 seconds and down for about 10 seconds but does sound smoother. I didn't want to leave it like this because the values just didn't seem correct, it made my map have a big high spot.

I will disconnect injectors one at a time later today and report back and yes 100% the x series wideband.

I'd also like to add that when driving under 10% throttle, the car also misfires and reads lean but anything more, it drives smooth and shows nice AFR again.

 

The only time it has gotten better was when I retarded the timing on my ignition map in the idle section. I was playing around and gave -50 retard next to a +14 deg advanced cell to play with a lumpy cam sound and the idle didn't oscillate like it does now, only when it is at "normal" ignition values the car idles funny.


I should have also mentioned in my first post I did advance my intake cam ever so slightly (with a VCT adjustment plate from boostdoc), before I did this the idle didn't oscillate at all.
So, since advancing the intake cam, the car doesn't want to stay at a particular idle target, also car turns off after about 30 mins of idling and will not start once ECT is above 90deg C.

I know it's a lot to read but I appreciate the effort and time you guys put into this forum.

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On 1/14/2022 at 3:57 AM, Adamw said:

Appears to be a misfire or fuel related issue to me.  Does it run smoother if you richen it up so the lambda is richer than stoich?  Is your wideband definitely an X series, not the older one?  Do you get a similar RPM drop if you disconnect one injector at a time?

Hi Adam,

I disconnected each injector while idling, it made the typical misfire, but still didn't replicate the big up and down of the idle.
Since posting, I have played with many idle settings, have been using open loop, changed base position while car is heating up, but once it gets above approx 80 deg it starts going up and down again.
It is fine from start up, up until around 75-80 deg C it starts playing up.

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In your last log idle valve position, ignition timing and injector PW were all reasonably stable.  If it is not just too rich or lean causing a misfire, then there appears to be some other influence outside of the ecu. 

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6 minutes ago, Adamw said:

In your last log idle valve position, ignition timing and injector PW were all reasonably stable.  If it is not just too rich or lean causing a misfire, then there appears to be some other influence outside of the ecu. 

Thanks Adam, I've got another idle valve at home I'll test that out when I go home.
I took another log just now while idling and noticed something, the only thing is the fluctuation in the battery voltage going from approx 13.5 and approx 13.2 but not sure where that is coming from

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On 1/15/2022 at 10:53 PM, Adamw said:

In your last log idle valve position, ignition timing and injector PW were all reasonably stable.  If it is not just too rich or lean causing a misfire, then there appears to be some other influence outside of the ecu. 

one note on this, from memory my RB25 manifold had 3 different idle solenoids with only one being ecu controlled, I know another was on with ac and I cannot remember what the 3rd did. Purple and Brown? solenoids at the back of the manifold and the straight through one with the black plug underneath the manifold

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3 hours ago, Vaughan said:

one note on this, from memory my RB25 manifold had 3 different idle solenoids with only one being ecu controlled, I know another was on with ac and I cannot remember what the 3rd did. Purple and Brown? solenoids at the back of the manifold and the straight through one with the black plug underneath the manifold

Hmm yeh I've only got the purple and black plug solenoid attached to the manifold, I've deleted that straight through one which I believe was for the cold start.
The thing I don't understand is it idled perfect before I advanced my intake cam slightly.


Tempted to just use no idle solenoid and just use the throttle stop screw to control idle to see if that solves the issue as it seems like its opening and closing when it just needs to stay steady.
It's not like your typical misfire, it drops down to about 700rpm and then up to 950/1000. I've adjusted so many settings, the idle is sort of steadier now but still goes lean and rich and you can hear a difference.

Regarding using no idle solenoid and just a throttle stop, would I zero out all values in the software and adjust the screw manually, recalibrate the TPS and thats all?

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Ok well I've sourced the problem, I need to clean my stupid rats nest wiring up, I separated all the wires in the loom close to the ecu and the problem went away.

If you're having issues similar I highly recommend checking your loom out.

Thanks everyone for your help!

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  • JOEL changed the title to SOLVED Strange Idle RB25

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