Idle Run Away

[[email protected]]

I have been struggling with trying to get my motor to idle, so I recently saw a YouTube video of Matt Sanford idle tune which uses speed density. When I applied this setup, the motor fired right up, but the idle started to run away. This is with no throttle added, so I did something wrong or something is wrong. When I was trying to run a tune with the MAF sensor, car would start but die 3 to 4 seconds later. 1 thing I have learned is my injector table is wrong in that my pressure regulator is vacuum referenced so my injector flow table should be flat. So when looking at this log and tune I know I need to change this. I just don't think that is what's causing my issue. Since I really don't know what a good log file is of a running ls 6.0l with a BT stage 2 cam I'm stumped as to what would cause this run away. Any ideas or maybe someone log file with a similar setup that I can compare to what I'm seeing.

Car spec's
Ls 6.0
BT Stage 2 Cam cam Specs: 227/238 .620"/.605" 113.5+2.5 #32738132R0
799 heads
AF10043 MAF SENSOR
AFS123 O2 sensors
02 Truck manifold with #25317628 injectors
Vacuum referenced regulator (fuel rail mounted old style)
4l80E
102mm throttle body (it was free I know it?s too big)
DURALAST AC162 IAC SENSOR
TH149 TPS SENSOR
P01 PCM 12208322 OS.

[edcmat-l1]

Put the laptop down and go figure out where the air is coming from. Not everything is fixable by tooning. Ya still gotta get the mechanicals straight.

[blindsquirrel]

Did you recently change injectors? Your changelog has some very weird shit in it. Was it wrong before and now been corrected, or was right before and is now wrong?

[blindsquirrel]

Did you run it before these changes to the tune file, or did you change a bunch of parts and the tune file at the same time?

[[email protected]]

Did you run it before these changes to the tune file, or did you change a bunch of parts and the tune file at the same time?

I bought this motor of a guy that tore it down and replaced the cam, springs in it. He had it on an engine stand running when I bought it, but he kept the computer, manifold ect.. Nothing else came with the motor besides the block and heads. I have pieced this together to what it is today. The Motor is in a 85ss, the PCM came from LS Solutions with a "idle" tune, but it had the wrong fuel injectors in the table.. So I did try to use the setup that came with the PCM (untouched) the car would start, but wouldn't idle. When I went to the Sanford setup it now starts and runs, but the idle just runs away. What I'm trying to figure out is what cause this run away. I know someone mentioned leaking, but a vacuum leak? Wouldn?t I see that in the Map sensor data? The log file I just sent is the longest this motor has run to date in this car.

So to answer your question, Yes, I tried to run the original tune file that LS Solutions had in the PCM. The asked about my motor and transmission and put a suitable OS / tune to get the car to just idle. this did not work, Car would start but die. I tried a few other things, nothing worked. That's when I went to the Sanford tune which caused the run away.

One thing to note is this motor has no exhaust yet. Trying to get it started before taking it to get this put on..

Thank you for any response... I know I'm over my head, but that's how everyone learns......

[[email protected]]

Did you recently change injectors? Your changelog has some very weird shit in it. Was it wrong before and now been corrected, or was right before and is now wrong?

Injectors data was wrong in the PCM that I bought. They had 50lb injector in the table.. I did not really put the correct values in when I changed it because I figured out that I have refernced Vacuum regulator not a dead head system like the table shows now.. Hope this answers your question..

[edcmat-l1]

The engine is getting a bunch of airflow from somewhere. Has nothing to do with anything toon related. Wrong injector data will not cause an engine to run at 3000 rpm @ zero TPS.

[[email protected]]

The engine is getting a bunch of airflow from somewhere. Has nothing to do with anything toon related. Wrong injector data will not cause an engine to run at 3000 rpm @ zero TPS.

Thank you for the response just one question, if I was getting a ton of air flow (leak) wouldn't the Map show a really high KPA value or I'm I looking at this backwards... I will look for a leak but I'm not sure how to find it when I can't get the engine to idle. Can I put smoke in the throttle body and see were a leak is??? It is weird...

screen grab .jpg

[blindsquirrel]

But this engine combo (the hardware) hasn't run properly since it was put together? So this isn't a case of where you changed the tune and then a problem showed up right afterwards. A new engine combo, with a complete unknown tune, and forced open loop, is a tough point to start from. Fully back to stock with the tune and making changes only for any changed hardware, and initial adjustments for the cam, and in closed loop, would be a more solid place to begin.

I've never heard of a way to use MAP readings as a sign of a vacuum leak. The engine uses a very small amount of air to idle, so a relatively small leak can be a large portion of what the engine would need. Normally, you'd look for abnormally low MAF readings (which you don't have), with (possibly) high idle with low IAC counts (if DBC) or low TPS% (if DBW) and low idle spark, all at the same time with lean fuel trims (which you don't have, because forced open loop) that get progressively less lean as RPM/throttle increases.

[abc]

if I was getting a ton of air flow (leak) wouldn't the Map show a really high KPA value or I'm I looking at this backwards... I will look for a leak but I'm not sure how to find it when I can't get the engine to idle. Can I put smoke in the throttle body and see were a leak is??? It is weird...

screen grab .jpg

Think of the MAP reading as more of an indication of load on the engine. The higher the MAP, the higher the load. You can have high RPM and light load, (which you have shown in your example) and of course low RPM and heavy load, then anything in between. MAP in a NA engine is basically a measurement of pressure differential from atmosphere psi and how much your intake is allowing that psi in vs how much the engine is using and it's efficiency in the process.

If your unsure of how to find the source of the air, first listen for it while the engine is running. If you can't hear it, shut the engine off, plug all vacuum related ports for the intake manifold to eliminate all the external vacuum loads such as brake booster, PCV valve and so on. If that doesn't do it, use a solid object to big to fit in the intake track and begin to close off the intake while it runs, a leak of that size should expose itself via sound. If you still haven't found it, google smoke machines for vacuum leak testing, you will find enough info. to proceed.

[[email protected]]

With advice Thank you.. I went back to the original tune that was in the PCM when I bought it. The only update was the fuel injector table to match my injectors. This also put the O2 sensors and MAF back in play. The car started, but the idle was still high 1,400 rpm ish.. but didn't seem to run away. I Then thought about the throttle body and figured I would close this off as much as possible. I removed the throttle cable, and backed out the throttle blade stop screw. The car started with a high idle but worked its way back to the idle table and actually idled. Not great, but it?s the first step I needed?. Need to work on getting the throttle cable back on and trying to readjust. But before going farther with the tune should I send out to have the exhaust completed before messing around with it anymore? I saw a post that open exhaust can affect O2 sensors.

I did include the log file in case anyone want to throw tips my way to improve the tune.. My next lesson will be trying to smooth this thing out..

[blindsquirrel]

There is a step by step process for setting the blade angle and TPS and relearning the IAC position. Fiddling things at random...

[gtstorey]

https://www.pcmofnc.com/2021/03/05/i...throttle-body/

[Alvin]

102mm throttle body (it was free I know it?s too big)
.

This would be what I suspect. The market is flooded with cheap poor performing chinese knock offs.

[horsepowerguru427]

Since this is a DBC throttle body that has been changed to a 102mm, have you adjusted IAC steps for the size difference? Id look in the tune and offer more precise advice, but i am not on my laptop and cant view it ATM.

https://forum.hptuners.com/showthrea...-HP-tuners-pro