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1,105 Posts
YW...................
Wont start when below 40 degrees outside.
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Well it was 34 this morning. Two days ago I changed the ECT sensor with a new OEM item. I meant to hook up reader before I started to see if it read true temp but I accidentally started it and it ran good. Maybe sensor was a fix but I’d like to see it get into the 20s before I get a fuzzy feeling it’s fixed. I’ll keep updated.
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Ok it was 27 out this morning and the issues still there. ECT sensor not the problem. May have to take to a shop and get a good scanner on it. Frustrating. Runs for 5-10 seconds and dies.
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OK .... dying AFTER starting is not the same as NOT STARTING. Your latest post shifts the responsible device to a different area.
It seems to be running lean ... or better yet ... it has a significantly large throttle body bypass problem.
I don't know for sure ... but does your engine use a MAF? Seems some 4,2s do, others don't. Thens there's also the consideration of a bad ISC .... again if your engine has one - mine doesn't
This might be something like an object stuck in the air butterfly ----- an errant toothpick or pencil .....
Need feedback.....
It seems to be running lean ... or better yet ... it has a significantly large throttle body bypass problem.
I don't know for sure ... but does your engine use a MAF? Seems some 4,2s do, others don't. Thens there's also the consideration of a bad ISC .... again if your engine has one - mine doesn't
This might be something like an object stuck in the air butterfly ----- an errant toothpick or pencil .....
Need feedback.....
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27 Posts
Yes I have a MAF sensor. So today my results were
35 ambient temp outside. Vehicle sat cold for 12 hours. My engine temp was 3 Celsius and my IAT was 8. That equates to about 45 F so there is defiantly a difference. Prior to changing the ECT sensor it was 9C at 35F outside. So the ECT did drop to being accuarate after I changed it.
Maybe it is my MAF sensor reading high and effecting timing while cold. Hate to spend $50 on a new one just to try it.
35 ambient temp outside. Vehicle sat cold for 12 hours. My engine temp was 3 Celsius and my IAT was 8. That equates to about 45 F so there is defiantly a difference. Prior to changing the ECT sensor it was 9C at 35F outside. So the ECT did drop to being accuarate after I changed it.
Maybe it is my MAF sensor reading high and effecting timing while cold. Hate to spend $50 on a new one just to try it.
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1,105 Posts
OK .... converting Silligrade to Fahrenheit .... so 9°Silligrade = 48.2°F, and 3°S = 37.4°F whatever ... so, yeah ... being off a bunch of degrees will definitely affect cold start ... and also running performance, but only up to a point.
It can cause either an enriched air:fuel mixture or one that is too lean... but only to preset operational parameters ... again: only up to the moment it goes Closed Loop.
The intake air temp helps in the simple computation to establish a "Look Up Value" affected by air density or ambient temperature and OBD2 Readiness parameters. There's more but I'll stop here.
Your problem appears ..... if my thermal calculations are even close to correct ... to be leanness... and that's a very unstable operating situation in cold temps.
After Closed Loop is established, things like the Oxygen Sensor(s) start getting chatty and the feedback sensors go Greenboard and the ECM takes over working on achieving the ultimate 13.7:1 ratio as a Golden Value. .
Air temperatures are important, but I am old school enough to believe that the O2 sensors become the master decider for operating the whole system, correlating all the incoming data to ultimately protect the cat.
If the cat fails, everything goes bad ---> emissions AND performance.
But that's just the way I was taught.
.
It can cause either an enriched air:fuel mixture or one that is too lean... but only to preset operational parameters ... again: only up to the moment it goes Closed Loop.
The intake air temp helps in the simple computation to establish a "Look Up Value" affected by air density or ambient temperature and OBD2 Readiness parameters. There's more but I'll stop here.
Your problem appears ..... if my thermal calculations are even close to correct ... to be leanness... and that's a very unstable operating situation in cold temps.
After Closed Loop is established, things like the Oxygen Sensor(s) start getting chatty and the feedback sensors go Greenboard and the ECM takes over working on achieving the ultimate 13.7:1 ratio as a Golden Value. .
Air temperatures are important, but I am old school enough to believe that the O2 sensors become the master decider for operating the whole system, correlating all the incoming data to ultimately protect the cat.
If the cat fails, everything goes bad ---> emissions AND performance.
But that's just the way I was taught.
.
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27 Posts
This makes total sense. Its basically seeing it warm outside and doesn't need to "choke" the engine for enriched fuel. Using your old school 
. Then I thinking once it runs for 5 sencong 3-5 times and dies the cylinders are warm enough for the lean fuel and it begins to run. It prob still lean but just enough to keep running. Guess I going to try the MAF. Thanks guys Ill keep yeah updates.
. Then I thinking once it runs for 5 sencong 3-5 times and dies the cylinders are warm enough for the lean fuel and it begins to run. It prob still lean but just enough to keep running. Guess I going to try the MAF. Thanks guys Ill keep yeah updates.
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27 Posts
Well finally fixed I think. Thanks for the advice guys.
Seems it was the MAF sensor giving false temps. Thanks again.
Seems it was the MAF sensor giving false temps. Thanks again.
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