Truck is running like crap


Nick nardi

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I have an 86 ford ranger manual 2.9 v6
I having a problem where it starts up very hard cranks cranks finally catches wether it’s warm or not runs fine on the highways and minimal stopping and going. When it idles for longer periods of times it starts doing this break up and power loss when it’s doing this it’s bucking like crazy when I rev it up it clears up until I stop at a light then it does it again I have no idea what is going on never had this problem with any other vehicle I’ve had very confused and stumpt any help would be great
 


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RonD

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Welcome to the forum

It reads like TFI(spark) module is on its last legs, common failure point
Normally its just associated with heat, but they can act up at any time when they are near end of life

For the slow starts try this
Turn key on, count to 3 turn key off, repeat this 3 times, THEN try to start engine
You could be losing fuel pressure when engine is off, the fuel pump only runs for 2 seconds with key ON, it won't run again until engine RPMs are above 400
But if you cycle key on and off 3 times you get 6 seconds of fuel pump run time
If its starts up quicker then you are losing pressure when key is off

That could be from a leaking FPR(fuel pressure regulator) on the engine, or a leaking Check Valve inside the high pressure pump in the frame rail

The leaking FPR may account for the stumbling as well, fuel pressure should be 30psi, but engine will run OK down to 15-20psi
FPR has a vacuum line attached to maintain equal pressure at idle(high vacuum) or when accelerating(low vacuum), if FPR is leaking a bit pressure may slowly drop to under 20psi and you get stumbling until you REV engine(drop vacuum down) and get pressure back up
 
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Nick nardi

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Welcome to the forum

It reads like TFI(spark) module is on its last legs, common failure point
Normally its just associated with heat, but they can act up at any time when they are near end of life

For the slow starts try this
Turn key on, count to 3 turn key off, repeat this 3 times, THEN try to start engine
You could be losing fuel pressure when engine is off, the fuel pump only runs for 2 seconds with key ON, it won't run again until engine RPMs are above 400
But if you cycle key on and off 3 times you get 6 seconds of fuel pump run time
If its starts up quicker then you are losing pressure when key is off

That could be from a leaking FPR(fuel pressure regulator) on the engine, or a leaking Check Valve inside the high pressure pump in the frame rail

The leaking FPR may account for the stumbling as well, fuel pressure should be 30psi, but engine will run OK down to 15-20psi
FPR has a vacuum line attached to maintain equal pressure at idle(high vacuum) or when accelerating(low vacuum), if FPR is leaking a bit pressure may slowly drop to under 20psi and you get stumbling until you REV engine(drop vacuum down) and get pressure back up
Ik I’m getting fuel pressure I just replace the FPR running a lot better now and I just replaced the map sensor that helped as well. I was thinking about getting an msd distributor
 

Dirtman

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So friggin big!
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PetroleumJunkie412

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RonD is waaaay better at this stuff than I am... But.


Have you pulled trouble codes from your ecm yet?


Make sure to wait a while after they repeat to check if there are stored codes
 

Nick nardi

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RonD is waaaay better at this stuff than I am... But.


Have you pulled trouble codes from your ecm yet?


Make sure to wait a while after they repeat to check if there are stored codes
Don’t have an obd1 code reader
 

PetroleumJunkie412

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Lol. If you'd read that, you can use a paperclip and count your dash lights blinking, or just use a regular test light.
 

Dirtman

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Told you he could help...
 

sheep herder

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I've got an OBD 1 code reader collecting dust in my junk pile. Maybe I should start peeing on it. :ROFLMAO:
 

4.0blue98

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I've got an OBD 1 code reader collecting dust in my junk pile. Maybe I should start peeing on it. :ROFLMAO:
I have one too, but thinking it'll be very valueble some day. My retirement OBD1 reader... ;)
 

PetroleumJunkie412

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I remember those days. Now I can plug my laptop in to my 1988 and my 2011. Forscan SUCKS compared to tunerstudio, though 😭
 

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I have one too, but thinking it'll be very valueble some day. My retirement OBD1 reader... ;)
I even have the book with mine. If people like @PetroleumJunkie412 would quit telling people that you don't need a reader, they'd be worth a lot more $.
 


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