running lean per tuner rt
Thread Starter
Pro
Joined: May 2001
Posts: 669
Likes: 7
From: New Jersey
running lean per tuner rt
After a 7 year fight to resolve an issue where my 89 wouldn't stay running at idle finally turned out be a ecm issue. New ecm and I have driven her 300 miles and counting.
Decided to hook up tuner rt and see it's running lean and need help to resolve this. I suspect its the aftermarket throttle body but how do i get it to not be lean since its fuel injected. Anyone have ideas?
Logs:
cold start
warm run
Car is basically stock 89 with 55k.
bbk 52mm throttle body
Someone replaced fuel injectors a long time ago no info on them
o2 replaced by someone else but basically new
Frisbee removed
Coolant throttle body bypass
180 degree stat
muffler eliminators
new ac delco plugs, cap , rotor, wires, iac, fuel pump, fuel filter, injectors changed by others,.
Decided to hook up tuner rt and see it's running lean and need help to resolve this. I suspect its the aftermarket throttle body but how do i get it to not be lean since its fuel injected. Anyone have ideas?
Logs:
cold start
warm run
Car is basically stock 89 with 55k.
bbk 52mm throttle body
Someone replaced fuel injectors a long time ago no info on them
o2 replaced by someone else but basically new
Frisbee removed
Coolant throttle body bypass
180 degree stat
muffler eliminators
new ac delco plugs, cap , rotor, wires, iac, fuel pump, fuel filter, injectors changed by others,.
Racer
Joined: Oct 2012
Posts: 280
Likes: 82
From: Indiana
Datalog while you drive for a few hours and review the data. If you know, and can, make changes to the bin file reprogram it. If not you can email you datalog to an online tuner and they can reflash your ecm. Odds are its your 52 mm throttle body allowing more air flow than what your ecm is programmed to see and is running lean because of it.
Drifting
Joined: Jul 2022
Posts: 1,805
Likes: 365
From: Central Florida
I think this is a paradigm for me. Unless something is bypassing the MAF, how does a self correcting system run lean ?? with a coolant temp sensor , a MAF, and an O2 sensor, I would think there couldn't be an imbalance unless integral or block learn were forced to their extremes and couldn't go any further. It is obvious that I am wrong, I seems to happen quite often.
Then there is a problem of DIY'rs like me trying to understand parameteres that seem OK. What is an O2 sensor showing as long as it is rich then lean? What is a MAf showing with increases grams per second as long as it seems consistant? I did like a lot others and pat myself on the back for learning so much but when it comes to reading and seeing a problem that isn't stuck at zero or stuck at 5vdc I have doubts about the nuances I am seeing from data. Where do we get/learn TPI streams so they tell us more than just absolute failure.
I can not see the OP's download but the same applies here, the O2 is bouncing rich lean, the MAF goes up and down why cant INT and BLM correct ????? What tells us what a perfect O2 graph is and where airflow should be and exactly what pulse width for fuel should be for a TPI ????
Then there is a problem of DIY'rs like me trying to understand parameteres that seem OK. What is an O2 sensor showing as long as it is rich then lean? What is a MAf showing with increases grams per second as long as it seems consistant? I did like a lot others and pat myself on the back for learning so much but when it comes to reading and seeing a problem that isn't stuck at zero or stuck at 5vdc I have doubts about the nuances I am seeing from data. Where do we get/learn TPI streams so they tell us more than just absolute failure.
I can not see the OP's download but the same applies here, the O2 is bouncing rich lean, the MAF goes up and down why cant INT and BLM correct ????? What tells us what a perfect O2 graph is and where airflow should be and exactly what pulse width for fuel should be for a TPI ????
Last edited by Vets-Vet; Jul 3, 2025 at 02:16 PM.
Melting Slicks
Joined: Aug 2003
Posts: 3,394
Likes: 393
From: Lakeville MI
It is not running lean.
From the warm run link, the overall running average BLM (from my History Table) is 129.82 (based upon 3476 samples or about 5 minutes). This is only about a 1.5% average correction. E10 fuel (for example) will run about 4% lean relative to 100% gasoline. A 1.5% correction is nothing.
The BLM vs cell (running average) range for all 16 cells runs from 126-132. I'd say it is spot on. There will always be some minor fuel correction no matter what you do with the tuning. Feel free to collect more data.
Note: the bin is APYZ according to the prom id 3571.
From the warm run link, the overall running average BLM (from my History Table) is 129.82 (based upon 3476 samples or about 5 minutes). This is only about a 1.5% average correction. E10 fuel (for example) will run about 4% lean relative to 100% gasoline. A 1.5% correction is nothing.
The BLM vs cell (running average) range for all 16 cells runs from 126-132. I'd say it is spot on. There will always be some minor fuel correction no matter what you do with the tuning. Feel free to collect more data.
Note: the bin is APYZ according to the prom id 3571.
Instructor
Joined: Jan 2019
Posts: 166
Likes: 33
From: Connecticut, USA
Melting Slicks
Joined: Jul 2005
Posts: 2,206
Likes: 302
After a 7 year fight to resolve an issue where my 89 wouldn't stay running at idle finally turned out be a ecm issue. New ecm and I have driven her 300 miles and counting.
Decided to hook up tuner rt and see it's running lean and need help to resolve this. I suspect its the aftermarket throttle body but how do i get it to not be lean since its fuel injected. Anyone have ideas?
Logs:
cold start
warm run
Car is basically stock 89 with 55k.
bbk 52mm throttle body
Someone replaced fuel injectors a long time ago no info on them
o2 replaced by someone else but basically new
Frisbee removed
Coolant throttle body bypass
180 degree stat
muffler eliminators
new ac delco plugs, cap , rotor, wires, iac, fuel pump, fuel filter, injectors changed by others,.
Decided to hook up tuner rt and see it's running lean and need help to resolve this. I suspect its the aftermarket throttle body but how do i get it to not be lean since its fuel injected. Anyone have ideas?
Logs:
cold start
warm run
Car is basically stock 89 with 55k.
bbk 52mm throttle body
Someone replaced fuel injectors a long time ago no info on them
o2 replaced by someone else but basically new
Frisbee removed
Coolant throttle body bypass
180 degree stat
muffler eliminators
new ac delco plugs, cap , rotor, wires, iac, fuel pump, fuel filter, injectors changed by others,.
That said, this is only for the side of the engine that the ECM can "see" with the O2 sensor. The passenger side will not affect the fuel trimming since the O2 is only on the driver side. Have you pulled spark plugs to see what they look like?
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Melting Slicks
Joined: Jul 2005
Posts: 2,206
Likes: 302
I think this is a paradigm for me. Unless something is bypassing the MAF, how does a self correcting system run lean ?? with a coolant temp sensor , a MAF, and an O2 sensor, I would think there couldn't be an imbalance unless integral or block learn were forced to their extremes and couldn't go any further. It is obvious that I am wrong, I seems to happen quite often.
Then there is a problem of DIY'rs like me trying to understand parameteres that seem OK. What is an O2 sensor showing as long as it is rich then lean? What is a MAf showing with increases grams per second as long as it seems consistant? I did like a lot others and pat myself on the back for learning so much but when it comes to reading and seeing a problem that isn't stuck at zero or stuck at 5vdc I have doubts about the nuances I am seeing from data. Where do we get/learn TPI streams so they tell us more than just absolute failure.
I can not see the OP's download but the same applies here, the O2 is bouncing rich lean, the MAF goes up and down why cant INT and BLM correct ????? What tells us what a perfect O2 graph is and where airflow should be and exactly what pulse width for fuel should be for a TPI ????
Then there is a problem of DIY'rs like me trying to understand parameteres that seem OK. What is an O2 sensor showing as long as it is rich then lean? What is a MAf showing with increases grams per second as long as it seems consistant? I did like a lot others and pat myself on the back for learning so much but when it comes to reading and seeing a problem that isn't stuck at zero or stuck at 5vdc I have doubts about the nuances I am seeing from data. Where do we get/learn TPI streams so they tell us more than just absolute failure.
I can not see the OP's download but the same applies here, the O2 is bouncing rich lean, the MAF goes up and down why cant INT and BLM correct ????? What tells us what a perfect O2 graph is and where airflow should be and exactly what pulse width for fuel should be for a TPI ????
That said, if you are getting high BLM's like into the 140's to 150's, then whatever is causing that is likely causing a lean condition during open loop when the ECM can't correct for it.
I think in power enrich though, the ECM will look at the BLM just prior to going into PE and richen the PE mixture accordingly (as a safety precaution against possible engine damage).
Melting Slicks
Joined: Aug 2003
Posts: 3,394
Likes: 393
From: Lakeville MI
Here's the warm log if anybody is still interested: https://datazap.me/u/tequilaboy/89-n...3-1153-3448-56
As you can see, there is hardly any BLM/INT activity other than the minor positive corrections already discussed. I'd say its pretty good for an un-tuned car running modern fuel. If you were to re-tune the target AFR for today's E10 fuel it would be just a tad rich, but not worth the effort unless you're one to obsess over the numbers (not that there is anything wrong with that).
As you can see, there is hardly any BLM/INT activity other than the minor positive corrections already discussed. I'd say its pretty good for an un-tuned car running modern fuel. If you were to re-tune the target AFR for today's E10 fuel it would be just a tad rich, but not worth the effort unless you're one to obsess over the numbers (not that there is anything wrong with that).
Racer
Joined: Feb 2024
Posts: 267
Likes: 113
From: New York
Dave
Melting Slicks
Joined: Aug 2011
Posts: 2,844
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