Hard start when hot
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Cross-Country
Joined: Jun 2003
Posts: 84
Likes: 4
From: Charlotte, NC
Hard start when hot
My 2005 F150 / 4.2L / manual starts fine when cold but has difficulty starting when it is shut off hot and allowed to heat soak for approximately 30 minutes. If it continues to cool off and is just warm (after an hour or so) it starts fine again.
When I say it has difficulty starting hot it will crank for 5-10 seconds before firing up and stumble for a few seconds before smoothing out.
No DTC's on the scanner. No leaks detected when I hooked up to the smoke machine.
One thing I did notice when looking at the live data at idle was that the STFT of both banks bounces between approximately 1.0% and -1.5% (I'm assuming is normal). However, the LTFT for bank 1 is about 3.9% but bank 2 is -10.1%. MAP is 9.7 inHg (seems low to me). When I got up to about 45 mph and in the throttle slightly, the STFT stayed about the same while the LTFT of bank 1 increased to around 5.5% and bank 2 increased to around 4%. The MAP also increased to approximately 18 inHg.
Do any of these numbers indicate a possibly problem with the injectors, etc.?
When I say it has difficulty starting hot it will crank for 5-10 seconds before firing up and stumble for a few seconds before smoothing out.
No DTC's on the scanner. No leaks detected when I hooked up to the smoke machine.
One thing I did notice when looking at the live data at idle was that the STFT of both banks bounces between approximately 1.0% and -1.5% (I'm assuming is normal). However, the LTFT for bank 1 is about 3.9% but bank 2 is -10.1%. MAP is 9.7 inHg (seems low to me). When I got up to about 45 mph and in the throttle slightly, the STFT stayed about the same while the LTFT of bank 1 increased to around 5.5% and bank 2 increased to around 4%. The MAP also increased to approximately 18 inHg.
Do any of these numbers indicate a possibly problem with the injectors, etc.?
Fleet Mechanic
Joined: Apr 2016
Posts: 1,653
Likes: 193
If you want to rule out injectors leaking , lay them out still in rail on dry newspaper turn key on none should leak . Its up to you to look at the condition of orings , would not hurt to change them all . Use motor oil on orings to seat them or you will find it difficult to press them into intake I would also look at mode six ,it will tell you the raw computer counts by each cyl that is being set towards a misfire . It also tells you the number its looking for to set a code which is quite high . You want zero counts .
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mdbelt
1987 - 1996 F150 & Larger F-Series Trucks
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May 26, 2010 02:01 PM
