Tmax Hot Start
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From: Woodstock, Ont , Can
Tmax Hot Start
On a hot start, just after shutting down it will rev to about 1500 and in about 1 second drop back to 944. Cold starts exibit normal cold increase with rpm drop as it heats up. Let it sit for 15-30 minutes it will rev up initially but only to about 1200 rpm and as it heats drops back to 944. I would like to eliminate this hot start higher rpm to within 50 or so and the best I can come up with is to edit the IAC vrs Temp map. My idea is to flat line the normal idle temp back to 107-150 range and smooth it into the colder temps. If someone could look over map 401 and see if this is causing the rpm gains on hot start, and see if this edit will do what I want, or is there somewhere else to look at. It has been initialized correctly, and since that any edits have been live.
Ron
Ron
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And I presume you've already validated your Cranking Fuel and Initial Fuel Pulse settings? If either is set too high it could have impact when hot, while still being within tolerance when cold IMHO.
Also, the Idle Speed vs. Engine Temperature page looks acceptable?
I'll take a look at 401 and see what I can see, and see if I can offer any input.
Roger
Also, the Idle Speed vs. Engine Temperature page looks acceptable?
I'll take a look at 401 and see what I can see, and see if I can offer any input.
Roger
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Roger: Yup, did the pulse and dropped it to 220 quite some time ago as well as the afr vrs temp. 401 is a lumpy bastard about 5 seconds after starting, then clears in about another 5 seconds and this was an attempt to make it run smoother on cold starts. It's close but could go leaner on the afr vrs temp next time I'm in there. Cranking fuel seems about right, because when I pulse it the night before, as it will only pulse once regardless of how many times the switch is turned on before and start strictly on cranking fuel the next morning it catches on about 4 revolutions and runs, followed with it's 5 second lumpy, then smooth. By doing a monitor at startup, I believe it initially runs about 11-11.5 afr which would account for that, which points to the afr vrs temp as the lumpy source.Eventually it leans to 13.7 at normal hot idle.
Got a handle on how all that works, and just need to figure out the hot iac thing and do it in one session.
Ron
Got a handle on how all that works, and just need to figure out the hot iac thing and do it in one session.
Ron
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You need to lower IAC home setting under basic settings. Most maps default from 80-100 for the home setting. This will cause the over rev on hot restarts. Try reducing this setting by 5 and do a hot restart, your rpms should be lower. You may need to play with the number to get it where you want.
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From: Woodstock, Ont , Can
You need to lower IAC home setting under basic settings. Most maps default from 80-100 for the home setting. This will cause the over rev on hot restarts. Try reducing this setting by 5 and do a hot restart, your rpms should be lower. You may need to play with the number to get it where you want.
I take it it's just a live edit with no initialize needed even though it's mucking with the iac ?Thanks for the quick answer.
Ron
Last edited by rbabos; Aug 8, 2008 at 06:16 PM.
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From: Woodstock, Ont , Can
I will let you know how it goes and how much of a change needed to make it right.
Ron
Last edited by rbabos; Aug 8, 2008 at 06:24 PM.
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I pasted the IAC info from the manual below. This setting is only used on initial startup and shouldn't effect the IAC table. It's basically adjusting the amount of air at closed throttle startup. Link to the Tmax, read your map, make change in basic setting and write changes to ecm. No initialization is necessary. Save a copy of the map on your computer. I had the same problem your experiencing and was able to correct it with this adjustment. Brett
IAC Home Position:
The IAC Home Position setting will determine how much air is required to pass by the
IAC motor for the engine to start without assistance of moving the throttle plate. This
value indicates the position (in counts) of the Idle Air Control (IAC) with the key in
RUN, without the engine running. This setting affects the amount of air the engine
receives while cranking thru the IAC port. The IAC Home Position range is from 0 (fully
closed) to 255 (fully open) counts.
IAC Home Position Tip: For 2001-2005 models, this value generally is
between 90 and 115 counts. On 2006 models with a factory throttle body,
58-70 counts is a standard value. A value that is too low wont allow the
engine to start properly. A value that is too high may require the engine to
crank excessively to start. If either situation exists, adjust the values by +/-
5 points at a time to test the starting improvement.
IAC Home Position:
The IAC Home Position setting will determine how much air is required to pass by the
IAC motor for the engine to start without assistance of moving the throttle plate. This
value indicates the position (in counts) of the Idle Air Control (IAC) with the key in
RUN, without the engine running. This setting affects the amount of air the engine
receives while cranking thru the IAC port. The IAC Home Position range is from 0 (fully
closed) to 255 (fully open) counts.
IAC Home Position Tip: For 2001-2005 models, this value generally is
between 90 and 115 counts. On 2006 models with a factory throttle body,
58-70 counts is a standard value. A value that is too low wont allow the
engine to start properly. A value that is too high may require the engine to
crank excessively to start. If either situation exists, adjust the values by +/-
5 points at a time to test the starting improvement.
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From: Woodstock, Ont , Can
Brett: I read that part but since it fires right off as soon as I hit the button I never thought that was the problem. Must be referring to settings that are really off in both extremes. What you say and how it works for home position starting makes sense now. It was always giving me the impression it used one setting to start hot and immediately jump to it's normal idle. Cold starts don't seem to show this behaviour. Could this be due to the cold start rpm being higher and it's less noticable ? I will give it a shot and see how it behaves. Thanks.
Ron
Ron
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From: Woodstock, Ont , Can
Update on hot idle start. Finally got around to dropping the iac home position by 5 points. Much better with only a very slight increase. Will probably take a couple more off down the road but for now quite accepatable.
Ron
Ron
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