5.3 air flow issues, tables maxed out
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5.3 air flow issues, tables maxed out Just recently rebuilt my 2001 5.3 with flat top pistons, Texas speed 224r cam and 8.1L injectors that I have in my jeep wrangler paired with a rebuilt 4l60e and a 2500 stall converter.
Trying to get it tuned right now and everything seems to be fine other than air flow. The only way we can get it to idle is with the vacuum line on top of the intake unplugged. Air tables are maxed out and still no good, MAP sensor is reading fine. The weird part is that it will idle with the vacuum line plugged in but only after driving it around for 15 minutes. I have the intake made out of 4" tubing wrapping around the throttle body then going straight back about 8" to a brand new filter.
Trying to get it tuned right now and everything seems to be fine other than air flow. The only way we can get it to idle is with the vacuum line on top of the intake unplugged. Air tables are maxed out and still no good, MAP sensor is reading fine. The weird part is that it will idle with the vacuum line plugged in but only after driving it around for 15 minutes. I have the intake made out of 4" tubing wrapping around the throttle body then going straight back about 8" to a brand new filter.
Incorrect idle speed airflow,
Disable or unplug the IACV and shut it down completely. Close it off somehow so the engine cannot breath from it.
Then raise the engine idle manually with a screwdriver (there should be an adjustment somewhere for idle airflow manual adjustment) it might be on the throttle body OR IACV depending on the engine.
Raise the idle manually until it is JUST BELOW the Fully warmed up temperature desired idle(engine must be fully warm 180*F+OIL temps). I.e. if you desire 900rpm idle, set the manual adjustment to 850rpm.
Then, re-plug in the IACV control and let the computer add the last 50rpm worth of airflow. That should take care of the low idle/problem when cold ("maxed airflow") if that was the issue. If I misunderstood maybe you should share more info like which ECU and provide a map for us to download.
Disable or unplug the IACV and shut it down completely. Close it off somehow so the engine cannot breath from it.
Then raise the engine idle manually with a screwdriver (there should be an adjustment somewhere for idle airflow manual adjustment) it might be on the throttle body OR IACV depending on the engine.
Raise the idle manually until it is JUST BELOW the Fully warmed up temperature desired idle(engine must be fully warm 180*F+OIL temps). I.e. if you desire 900rpm idle, set the manual adjustment to 850rpm.
Then, re-plug in the IACV control and let the computer add the last 50rpm worth of airflow. That should take care of the low idle/problem when cold ("maxed airflow") if that was the issue. If I misunderstood maybe you should share more info like which ECU and provide a map for us to download.
If this is a stock intake and stock throttle body, the issue is not with the throttle body or IAC, at least not such that you need to do what was mentioned above. Stock parts will deliver plenty of air as-is. And I don't think you will find an idle adjustment screw.
I would perform an IAC relearn to make sure it is where it is supposed to be.
I am not sure if starting with an 8.1 tune will work. I would have started with a 5.3-5.7 tune and used the injector data from the 8.1. IAC scaling might be different with the 8.1.
Also you will have to make sure that the fuel system is the same for the injector data to be correct. As in, return vs returnless, that will throw the data off.
What is weird to me is that it will idle with the vacuum line unplugged, which would indicate rich mixture or insufficient air, but it will idle after it warms up which would indicate it was lean.
I would perform an IAC relearn to make sure it is where it is supposed to be.
I am not sure if starting with an 8.1 tune will work. I would have started with a 5.3-5.7 tune and used the injector data from the 8.1. IAC scaling might be different with the 8.1.
Also you will have to make sure that the fuel system is the same for the injector data to be correct. As in, return vs returnless, that will throw the data off.
What is weird to me is that it will idle with the vacuum line unplugged, which would indicate rich mixture or insufficient air, but it will idle after it warms up which would indicate it was lean.
Thread Starter
Teching In
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Stock throttle body and intake with a return fuel system. IAC is like the 1 sensor in this stupid thing that I have not replaced yet. Before the rebuild I was having similar issues but keeping it revved at like 1500 rpms for 30 seconds and it would idle just fine. So if the problem still exists and everything else was replaced/rebuilt now the problem is just getting amplified with the cam and injectors?
Very well could be. Sometimes they just get covered with sludge and can be cleaned with carb cleaner, I would try that first.
Then do the IAC relearn.
Copied from another post;
Put key in ON position
Unplug IAC
Turn key off
Wait 30 seconds
Turn key on, leave on for 30 seconds. You should see a SES light now too.
Turn key off.
Plug IAC back in.
Turn key on.
Then do the IAC relearn.
Copied from another post;
Put key in ON position
Unplug IAC
Turn key off
Wait 30 seconds
Turn key on, leave on for 30 seconds. You should see a SES light now too.
Turn key off.
Plug IAC back in.
Turn key on.
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Thread Starter
Teching In
Joined: Jun 2016
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Very well could be. Sometimes they just get covered with sludge and can be cleaned with carb cleaner, I would try that first.
Then do the IAC relearn.
Copied from another post;
Put key in ON position
Unplug IAC
Turn key off
Wait 30 seconds
Turn key on, leave on for 30 seconds. You should see a SES light now too.
Turn key off.
Plug IAC back in.
Turn key on.
Then do the IAC relearn.
Copied from another post;
Put key in ON position
Unplug IAC
Turn key off
Wait 30 seconds
Turn key on, leave on for 30 seconds. You should see a SES light now too.
Turn key off.
Plug IAC back in.
Turn key on.
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Teching In
Joined: Jun 2016
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Very well could be. Sometimes they just get covered with sludge and can be cleaned with carb cleaner, I would try that first.
Then do the IAC relearn.
Copied from another post;
Put key in ON position
Unplug IAC
Turn key off
Wait 30 seconds
Turn key on, leave on for 30 seconds. You should see a SES light now too.
Turn key off.
Plug IAC back in.
Turn key on.
Then do the IAC relearn.
Copied from another post;
Put key in ON position
Unplug IAC
Turn key off
Wait 30 seconds
Turn key on, leave on for 30 seconds. You should see a SES light now too.
Turn key off.
Plug IAC back in.
Turn key on.
He did say that he was getting a good reading from the IAC but any sort of change to it in the tune made no difference. Going to try a new IAC in the morning and go from there.
Thread Starter
Teching In
Joined: Jun 2016
Posts: 20
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If anything this made it worse haha. 70% of the time it will start right up without any throttle and idle just fine (with the vacuum line disconnected) but at any blip of the throttle it won't idle anymore and just die. Seems the 30% that it doesn't idle after start up happens when it's warm
He did say that he was getting a good reading from the IAC but any sort of change to it in the tune made no difference. Going to try a new IAC in the morning and go from there.
He did say that he was getting a good reading from the IAC but any sort of change to it in the tune made no difference. Going to try a new IAC in the morning and go from there.