CK5
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Understanding the warmup of cold Tbi..
- Thread starter only 31s
- Start date
My remote start is, fire it up, pull the key out and lock the doors. Walk away.
I do like that part, when I do it...
As of now that's mine too ...
MEANSTREAK K30
1/2 ton status
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- Feb 26, 2016
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Is the check engine light on, or does it come on , then go off?
No codes......
MEANSTREAK K30
1/2 ton status
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Well , that is what I thought, as you would have said that in your first post. What is the next thing to check then? Or are you going to just drive it?
oh yeah... ive actually got to drive it alot in the past couple months[gas prices low-] im goona play and see if i can do some silly stuff[some how do a coolant preheat to see if the coolant sensor is the dominant that alows the cold idle drop] maybe an old coffee mug heating element into a coolant port somewhere....just for giggles..Thanks..I will post when I have some results....
black dawg
1/2 ton status
you can slow the fast idle down some by adjusting the throttle plates closed a little more. The ecm doesnt have a target fast idle speed, just commanded iac counts.
What is it you dont like about the fast idle? If everything is adjusted correctly you really shouldnt notice it much once you start driving. If base idle is adjusted too high or timing set advanced from spec, it will fast idle too fast.
What is it you dont like about the fast idle? If everything is adjusted correctly you really shouldnt notice it much once you start driving. If base idle is adjusted too high or timing set advanced from spec, it will fast idle too fast.
454Sub
5/8 ton status
The number one cause of slow Closed Loop operation is a cold o2. Install a heated one, and it will close the loop. With snow on the ground, my Suburban hits closed loop in under 2 minutes.
MEANSTREAK K30
1/2 ton status
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Are you certain on that? From what I'm seeing (and to be fair, I don't have a '747 ECM .bin in front of me) there is an idle speed temp correction table. http://www.gearhead-efi.com/Fuel-In...o1-by-Bruce-Plecan-AKA-quot-Grumpy-quot-R-I-P
black dawg
1/2 ton status
Honestly, I am not sure...but any increase of min throttle opening will increase fast idle speed, also advancing or retarding timing will affect it. Doesnt act to me like the ecm has a goal for fast idle speed, just programmed iac counts per temp.
I wish they did, as I like to adjust throttle setting so the Iac is under 10 steps (usually try for under 5) fully warmed up. Makes for nice smooth idle (better air fuel mix past the plates) and quicker starting. This in turn makes the fast idle faster (some more than others).
I wish they did, as I like to adjust throttle setting so the Iac is under 10 steps (usually try for under 5) fully warmed up. Makes for nice smooth idle (better air fuel mix past the plates) and quicker starting. This in turn makes the fast idle faster (some more than others).
I know TPI has specific RPM idle settings which I believe are four stage (cold, warm, up to temp, overheating) but I also know that TBI was generally a bit less "refined" than TPI. If I get any time I'll open up a '747 bin and check. But I'm almost certain the idle RPM is set within the bin. The IAC is used to achieve and maintain that RPM (ignoring other factors of course), but it pretty much has to be RPM that is used to govern IAC, not the other way around. Otherwise there would be problems when it drive was selected from park.
black dawg
1/2 ton status
I agree that the ecm has a target idle speed at operating temp, and the IAC tries to maintain that speed. what I was getting at was that I like to set the throttle plate opening to just slightly below that (target idle speed) so that the iac opening at hot min idle is very small. If you set the minimum throttle opening by the book, they dont idle quite as smooth because less airflow past the plates, an fuel doesnt get mixed in as well.
With my p/n switch being out of adjustment the idle will stay high until I use my park or nuetral,which would sometimes be 20 mins or more of highway driving( I'm 2 mins from highway ) has to be a huge waste of fuel... Only 10 mpg highway...wish I could get more...
If I understand what you are saying properly, your fast idle isn't going to have an effect on MPG on the highway.
FWIW, here are some of the things that govern idle speed within the '747 ASDU bin (5.7L TBI)
WoW ! are you trying to give me a heart attack or a hard on! Thats some sexy info right there....i know the mpg s wouldnt suffer much but unless i come to a complete stop and keep my foot on the brake in d it will stay high idle....of course if i stop and put into p or n its about a30 second drop--- on the exit-most of the problem is somebody is usually up my bumper by then- even at 530 Am....... [They dont call them MASS HOLES for nothin!!!] i just didnt want to tackle my p/n switch in the column. + my braking is effected with the high idle and stopping, it aint the best anyways and just worse down an exit towards the end .....If I understand what you are saying properly, your fast idle isn't going to have an effect on MPG on the highway.
FWIW, here are some of the things that govern idle speed within the '747 ASDU bin (5.7L TBI)
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chulisohombre
1/2 ton status
Have you tested any of the sensors. Sounds like your o2 isn't working correctly. If it heats up faster it will go into closed loop. If it's not already, try a heated one as was suggested.
chulisohombre
1/2 ton status
A definition and how and when a gm engine goes into closed loop. CLOSED LOOP – Closed Loop is a term in which the ECM uses feedback from the O2 sensor to make corrections to the air fuel ratio. Another name for this term is short term fuel trim. The ECM makes immediate but temporary corrections to the fuel delivery to maintain the AFR at 14.7. The only ratio that can be maintained in closed loop is 14.7. This is due to the nature of the type oxygen sensor used on most passenger cars. There are other types of O2 sensors called wide band sensors, but they are expensive. They can be used to monitor the AFR at other than 14.7 AFR. The short term fuel trim value is called the Integrator in most early scantools. The value of the integrator varies above and below 128 with 128 being no correction. For ex., if the integrator is 140, the ECM is adding fuel because the O2 sesnor is reading a lean mixture. If the Integrator is 115, the ECM is removing fuel because the O2 sensor is reading a rich mixture. Anytime the system is not in closed loop, the Integrator will immediately return to a value of 128 and stay there. There is only one Integrator and its value is solely dependent on the O2 sensor. When the engine is started, the ECM will keep the Integrator at 128 until the ECM determines that the O2 sensor is working correctly and that the engine temperature and time delays before entering closed loop constraints have been satisfied. The problem with the Integrator is that its value cannot be used to determine how far away from 14.7 AFR you are. The value of the Integrator does however increase or decrease the longer you are above or below the 14.7 AFR. The time aspect is probably where the Integrator gets its name. If you have studied calculus, you'll know what I mean. Otherwise, its beyond the scope of this document to explain. The Integrator and BLOCK LEARN work together to re-tune the system to match any engine's charactersitics, up to a practical limit.
Hope this helps.
Hope this helps.
