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  #1  
Old 11-25-2015, 12:27 PM
illesg illesg is offline
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Default Hot start weirdness

OK, I need all the brain help I can get on this one.

Hot starting problem - - everything runs great around town, on the highway, etc. Then I stop and park, come back later and the engine will barely start. BUT - - - here's the weirdness:

This ONLY happens on days when the outside temperature is 75-90F. Colder, or hotter, it doesn't happen.

It ONLY happens between 10-20 minutes after stopping. If I get back sooner or later, it doesn't happen.

On cooler days or for a brief stop, it will run rough (4-5 cylinders). On warmer days or for that 20-minute stop, it will run on only 2-3 cylinders if at all. Sometimes takes 5-6 cranking sessions to get running on 2 cylinders.

AND - - - after about one minute of rough running, it all gradually clears up and runs great again.

Needless to say, I'm pulling my hair out (what little is left). Coil pack, plugs, wires, air cleaner, fuel filter, fuel pressure regulator. No CEL, no codes. Fuel pressure looks fine 30/40 with the vacuum test.

Any new ideas? I'm totally stumped.
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Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #2  
Old 11-25-2015, 04:41 PM
Jswifto Jswifto is offline
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Default

Clean your MAF
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  #3  
Old 11-25-2015, 06:05 PM
illesg illesg is offline
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Default Re: Hot start weirdness

Yup, cleaned the MAF too. Cleaned the throttle body. Checked operation of TPS. Also cleaned the intake-air temperature sensor, checked the whole intake tract for leaks, etc. A while back I changed out both temperature sensors and the problem went away, hoorah!

But a couple of months later it came back. Then, this year, it went away on its own for a month, then came back again.

Dang.
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==================
Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #4  
Old 11-26-2015, 05:59 AM
Jswifto Jswifto is offline
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What year is the truck ( I am using my phone so I cannot always see a sig) ? Sounds like vapor lock almost.
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  #5  
Old 11-26-2015, 11:02 AM
illesg illesg is offline
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Default Re: Hot start weirdness

It's a 96. Yeah, I thought about vapor lock but it's hard to test for that.
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Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #6  
Old 11-26-2015, 11:55 AM
Jswifto Jswifto is offline
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Next time it does it loosen your gas cap
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  #7  
Old 11-27-2015, 10:31 AM
illesg illesg is offline
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Default Re: Hot start weirdness

Well THERE is a weird experiment. I'll give it a try. Are you thinking vacuum or pressure in the fuel tank?
__________________
==================
Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #8  
Old 11-27-2015, 10:37 AM
Jswifto Jswifto is offline
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Yep
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  #9  
Old 11-28-2015, 08:27 AM
modelageek modelageek is offline
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Default Re: Hot start weirdness

Disconnect the MAF and see if it runs better. Do you have Torque? Can you get MAF readings?
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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

Last edited by modelageek; 11-28-2015 at 08:30 AM.
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  #10  
Old 11-28-2015, 11:09 AM
illesg illesg is offline
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Default Re: Hot start weirdness

Disconnect MAF, huh.... will that throw a code?

Yes, I have Torque, but I am not familiar with MAF readings specifically.
__________________
==================
Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #11  
Old 11-29-2015, 02:36 PM
illesg illesg is offline
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Default Re: Hot start weirdness

Well, it's in the 50's for high temps these days, so I'm not going to be able to run any experiments for a while. If anyone thinks of anything to look at, let me know...
__________________
==================
Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #12  
Old 11-29-2015, 03:17 PM
modelageek modelageek is offline
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Default Re: Hot start weirdness

Quote:
Originally Posted by modelageek View Post
Disconnect the MAF and see if it runs better. Do you have Torque? Can you get MAF readings?
Quote:
Originally Posted by illesg View Post
Disconnect MAF, huh.... will that throw a code?

Yes, I have Torque, but I am not familiar with MAF readings specifically.
That geek guy had a pretty good idea! Maybe he's familiar with the MAF readings? Especially g/s (grams per second)

----------

Quote:
Originally Posted by illesg View Post
Disconnect MAF, huh.... will that throw a code?

Yes, I have Torque, but I am not familiar with MAF readings specifically.
Yes disconnecting the MAF will throw a code! But if you disconnect the MAF the truck should run worse and eventually stall. If it runs better then the MAF is probably bad. Hillbilly DX FTW!

----------

Quote:
Originally Posted by illesg View Post
OK, I need all the brain help I can get on this one.

Hot starting problem - - everything runs great around town, on the highway, etc. Then I stop and park, come back later and the engine will barely start. BUT - - - here's the weirdness:

This ONLY happens on days when the outside temperature is 75-90F. Colder, or hotter, it doesn't happen.

It ONLY happens between 10-20 minutes after stopping. If I get back sooner or later, it doesn't happen.

On cooler days or for a brief stop, it will run rough (4-5 cylinders). On warmer days or for that 20-minute stop, it will run on only 2-3 cylinders if at all. Sometimes takes 5-6 cranking sessions to get running on 2 cylinders.

AND - - - after about one minute of rough running, it all gradually clears up and runs great again.

Needless to say, I'm pulling my hair out (what little is left). Coil pack, plugs, wires, air cleaner, fuel filter, fuel pressure regulator. No CEL, no codes. Fuel pressure looks fine 30/40 with the vacuum test.

Any new ideas? I'm totally stumped.
When it is running on 2,3 or 4 cylinders it must throw a code? At least a pending code? Any codes? Pending codes will not throw a CEL. Did you actually check for codes? Did you read the fuel trims at all?
__________________
2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

Last edited by modelageek; 11-29-2015 at 03:21 PM.
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  #13  
Old 11-30-2015, 07:02 PM
illesg illesg is offline
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Default Re: Hot start weirdness

NO codes ever. Don't know what "fuel trims" are. Didn't know there was such a thing as a pending code. Torque just lets me read the codes and displays whatever is there. But since I never saw a CEL, I never tried to read any codes.
__________________
==================
Nearly stock 1996 STX 4.0 automatic
6" lift & 31" tires, 4.11's, snorkel,
locker rear end, aluminum wheels
Lots of light-weight changes (towed behind RV)
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  #14  
Old 01-23-2016, 05:11 PM
alcom alcom is offline
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Join Date: Jan 2016
Posts: 1
Default Re: Hot start weirdness

Have hard start after driving for 20 minutes,runs rough,have had injectors cleaned,newfuel filter,plugs,wires,gas cap replaced. Mechanic put in BG44 fuel system cleaner in and cures problem short term.Has no codes or check engine light. 1994 Ranger 4.0
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  #15  
Old 01-24-2016, 05:18 AM
bjurke bjurke is offline
Ford Tough
 
Join Date: Jul 2011
Posts: 350
Default Re: Hot start weirdness

there is a possibility you have a fuel supply issue. you say your fuel pressure is ok but i assume you checked it with your engine running. was it checked just before you start it? possibilty check valve is leaking and fuel pressure too low on restart. try cycling your ignition key 3-4 times when you have these starting issues. one other possibility is extremely poor quality fuel. consider buying somewhere else. had problems like this with a 1993 mercury topaz years ago.
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