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The Problem:
Rough Surging Idle, Lean Idle after replacing wideband o2 because the wires were ripped out of old o2 sensor, Lean low speed cruise
The Car: i own a 92 1.6 car, stock internals, sequintial injection, vTPS, flyin miata manifold and DP combo, gt2554r, ms2pnp, walbro 255, FF 640cc, and has only half an exhuast as i have yet to buy or make a full exhaust, the car has been in this form for about 4k miles and has seen all track use with the exception of a month or two of daily driving and street tuning and driving to and from the track
The Background info: During my last weekend at the track, i adventured off track into the grass, while not completely terrible, the slip fit connection on my partial exhaust rotated 180degrees despite being tight, and all my o2 sensor wires were ripped out of my sensor. this is what i get for not having an exhaust or at least one long enough to use exhuast hangers to stop this. while i did not notice this on the gauge at the time, i got back on track, felt out the alignment and got back to work! After the lap i noticed my car tried to die when i clutched in and the revs dropped which hasnt happened since before i started tuning the ms2, i also noticed a rough surging idle and noticed a new error code on my innovate gauge E1 or no sensor connection. After a quick inspection i figured out i ripped the wires out of my sensor and sat out and watched the rest of the weekend. On the way home my idle kept surging and got worse to the point it was dying at stop lights. Once home, i ordered another bosch o2 sensor and installed it, now receiving the same error code e1.
My Attempt to remedy: at this point i checked all my wiring and grounds for the wideband and bought a brand new aem 30-4110 because i figured the old handmedown innovate had bit the dust or i received a bad new sensor, now with the aem wideband installed i still have this surging idle and now can see that it is due to an extreme lean condition. so lean the gauge wont even read it at some points,. still surging from 700- 1500 sometimes better sometimes worse. i took a data log and noticed a few out of place things i believe, first when idling my battery voltage as displayed in megalog viewer surges with the MAP from 13.1V to 13.9V not sure if this is normal or not seems suspicious. second i see either some noise or something in my TPS reading at idle or something is causing it to change when im off throttle, it bounces for -1.5%to1.5% rapidly i started with an alternator test which showed i was making 14V constant regardless of RPM with the engine running, battery tested at 14.75with the engine off. TPS in TS seems smooth if i watch the gauge and play with the pedal i re calibrated it as well just for kicks to no avail, i checked base timing still at 10deg, i see my fuel pressure gauge start at 0 move to 30-35psi on the prime and to 41psi at idle, i checked the fuel filter which is less than a year old and nothing but clear fuel came out either end when applying air to either side, i used some starter fluid to check for possible vacuum leaks, i am stumped at this point so i added 60% to the VE fuel cells at and around idle and she started idling a ton smoother still surging a bit around 15-16.5:1 i took a log while driving around the neighborhood just to get a log and see nothing out of the ordinary.
I got got half way through the wall of words, then lost my place and drowned.
Im very sorry i typed this in a hurry i can try to repost with a some better structure maybe later im just trying to get some headway on this issue before the weekend is out
I'm going to throw out a couple of things I see, but nothing definitive.
1) I've never seen an idle at 12kPa. Seems low? My '99 idles at around 25, at 800 RPM.
2) Did you re "calibrate" your AFR to account for the change from Innovate to AEM controller?
3) Other than those two things, I'm not much help. I don't know much about MS2's and less about NA idle valves.
Really, the readings of your WB should not be affecting idle as you have EGO turned off.
I know you said you checked grounds, but that would be my first guess.
Location: Detroit (the part with no rules or laws)
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This may sound a little stupid, but have you made sure that all your manifold / turbo / downpipe bolts haven't loosened up? I've had this cause wonky issues with AFR, even when the bolt / stud was quarter turn loose.
This may sound a little stupid, but have you made sure that all your manifold / turbo / downpipe bolts haven't loosened up? I've had this cause wonky issues with AFR, even when the bolt / stud was quarter turn loose.
@Erat I have not physically checked with a wrench, i do have locking hardware on the turbo flange and nord lock washers on the manifold-> engine and turbo->downpipe i have not noticed any exhaust leaks ive checked with a small mirror around as many edges as i can get to and see
Location: Detroit (the part with no rules or laws)
Posts: 5,677
Total Cats: 800
Yeah nord locks mean **** on vibrating boosted BP's. They help but only to a certain extent, i literally just went out and gave a quarter turn to all of mine. One was almost a full turn loose.
I'm going to throw out a couple of things I see, but nothing definitive.
1) I've never seen an idle at 12kPa. Seems low? My '99 idles at around 25, at 800 RPM.
2) Did you re "calibrate" your AFR to account for the change from Innovate to AEM controller?
3) Other than those two things, I'm not much help. I don't know much about MS2's and less about NA idle valves.
Really, the readings of your WB should not be affecting idle as you have EGO turned off.
I know you said you checked grounds, but that would be my first guess.
In for what the more knowledgable folks say.
DNM
@DNMakinson I did recalibrate to the new Aem controller, they gauge and TS read exactly the same(not that this pertains)
Also if you look at the last log i posted(first reply to the thread) my car used to idle smooth at 1000 rpms 15-20kpa 14:1afrs
In my tune you can see how high the fuel Value on the VE Table has to be at idle, higher than even maximum boost values, ive done this to make the smooth idle. But after 30minutes or so, the idle begins to become leaner and leaner until the surge returns
Before this problem values for idle cells were low 120s on the VE table
I feel like a vacuum leak is my problem but i have searched and searched and sprayed half a can of starting fluid around all the vacuum lines and intake manifold. Even sprayed around the vacuum line that hooks to the megasquirt ecu for the map sensor
Yeah nord locks mean **** on vibrating boosted BP's. They help but only to a certain extent, i literally just went out and gave a quarter turn to all of mine. One was almost a full turn loose.
@Erat No doubt! i will be sure to check all of the hardware and report back to you
Yeah nord locks mean **** on vibrating boosted BP's. They help but only to a certain extent, i literally just went out and gave a quarter turn to all of mine. One was almost a full turn loose.
@Erat Update all hotside hardware is tight and secure as well as intake manifold and throttle body hardware
I am convinced that you have 2 unrelated issues. The AFR is an issue with an air leak, or simply the fact that you have a truncated exhaust. The reading is false.
The other issue is related to the lying MAP reading. Since MAP is a direct multiplier in the MS fueling equation, when you get 1/2 the MAP, you will get 1/2 the fuel (Assuming dead time is 100% correct).
This is from your log 2020-09*13_12.33.51: Notice that as the MAP goes from 9 to 33, the fueling PW goes from 1.538 to 2.890. That is a huge bunch of extra fuel. And, if you notice, the PWM Idle Duty is constant. The car has gone out of CLI. See Status 2 = 0. That tells the same story. In other places in this log, the car is in CLI, so I don't think coming in and out is the issue.
Also, the RPM is going down as he MAP is going down. A leak would be the opposite. So would stalling. As the RPM goes to zero, the MAP goes to 100. Maybe not at 600 RPM, but eventually.
That is why I remain skeptical of the validity of your MAP readings.
EDIT. You mention rough idle. Could this be a mis-fire? That will cause false high AFR's. Still I ruled that out because adding fuel would not tend to fix it.
DNM
I am convinced that you have 2 unrelated issues. The AFR is an issue with an air leak, or simply the fact that you have a truncated exhaust. The reading is false.
The other issue is related to the lying MAP reading. Since MAP is a direct multiplier in the MS fueling equation, when you get 1/2 the MAP, you will get 1/2 the fuel (Assuming dead time is 100% correct).
This is from your log 2020-09*13_12.33.51: Notice that as the MAP goes from 9 to 33, the fueling PW goes from 1.538 to 2.890. That is a huge bunch of extra fuel. And, if you notice, the PWM Idle Duty is constant. The car has gone out of CLI. See Status 2 = 0. That tells the same story. In other places in this log, the car is in CLI, so I don't think coming in and out is the issue.
Also, the RPM is going down as he MAP is going down. A leak would be the opposite. So would stalling. As the RPM goes to zero, the MAP goes to 100. Maybe not at 600 RPM, but eventually.
That is why I remain skeptical of the validity of your MAP readings.
EDIT. You mention rough idle. Could this be a mis-fire? That will cause false high AFR's. Still I ruled that out because adding fuel would not tend to fix it.
DNM
@DNMakinson Mmm i had not noticed this on the log, is there a way to test the internal map sensor on the ms2? Or should i just take the cheapest route and replace the vacuum hose for the sensor?
A misfire is so simple and ive not yet thought about this, only because the engine seems to run smooth through all other conditions besides idle and light cruise. I did have to add something like 60% to my existing tunes VE fuel table in the idle region to get the idle afr to mid 14s as mentioned before after about 30 mins of this the afr rises and around 16:1 idle begins to surge likely due to incomplete exhaust system
09-13-2020, 02:37 PM
After Track Day Very Lean Idle and Cruise
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