Misfire at idle 300 i6 f150

[Orangepeel]

The regulator actually keeps the pressure from going too high, so if it's not leaking , it's ok. . That's why the pressure should increase by disconnecting the regulator's vacuum. You can check for a weak pump by disconnecting the regulator's vacuum and monitor the fuel pressure as you goose the throttle. If the pressure drops a lot (10 psi or greater) then springs back up, the associated pump is weak.

I go by what my factory manuals state. For 1987-1994 300's the idle pressure should be 45-60. On 1995-1996 the pressure should be 30-45 psi at idle. 1996 was the last year that beast engine was made.

You have a lean miss as indicated by your highly positive long term fuel trims. Don't pay much attention to the short term trims.The computer is adding a lot of additional fuel to maintain proper air/fuel mix. Low fuel pressure, stuck EGR, exhaust leaks upstream from O2 sensor, major vacuum leaks or bad data from a sensor.

Both are from direct hit which do you trust? Hard to verify and properly check things when the information isn’t even confidence inspiring.

 

[Joba27n]

Both are from direct hit which do you trust? Hard to verify and properly check things when the information isn’t even confidence inspiring.

This source has served me well since I left the dealer

 

[Lubener]

Both are from direct hit which do you trust? Hard to verify and properly check things when the information isn’t even confidence inspiring.

View attachment 295662

View attachment 295663

You are making a mountain out of a mole hill. My source is the Ford factory service manual. You can't get any more reliable information than that.

You don't pay attention. Your first screen shot is for 1995-1996 engines which applies to yours. The second screen shot applies to 1987-1994 engines which utilized a higher fuel pressure and different injectors..

 

[Orangepeel]

You are making a mountain out of a mole hill. My source is the Ford factory service manual. You can't get any more reliable information than that.

You don't pay attention. Your first screen shot is for 1995-1996 engines which applies to yours. The second screen shot applies to 1987-1994 engines which utilized a higher fuel pressure and different injectors..

Your dead ass wrong! Both are from the same vehicle with vin number inserted in the search. Have you ever used direct hit?
Direct hit identifix is where this info is from with the vehicle by vin inserted just because it doesn’t match your assumptions of what is accurate doesn’t mean i am not paying attention.

 

[Orangepeel]

You are making a mountain out of a mole hill. My source is the Ford factory service manual. You can't get any more reliable information than that.

You don't pay attention. Your first screen shot is for 1995-1996 engines which applies to yours. The second screen shot applies to 1987-1994 engines which utilized a higher fuel pressure and different injectors..

Fuel injectors show compatibility between years and this is the fuel pressure from ford per identifix. Also please explain how needing to know the proper fuel
Pressure is making a mountain out of a mole hill? A difference of 20psi is definitely going to make a difference. It is imperative to have the right information when performing diagnostic testing.

 

[Orangepeel]

This source has served me well since I left the dealer

They have the same specs as identifix that’s a little more reassuring.

 

[Lubener]

Your dead ass wrong! Both are from the same vehicle with vin number inserted in the search. Have you ever used direct hit?
Direct hit identifix is where this info is from with the vehicle by vin inserted just because it doesn’t match your assumptions of what is accurate doesn’t mean i am not paying attention.

I suggest you take your truck to a competent technician and get it fixed.. You are just spinning your wheels and not getting anywhere.

 

[Orangepeel]

I suggest you take your truck to a competent technician and get it fixed.. You are just spinning your wheels and not getting anywhere.

Would you like to pay for that? The fuel pressure is low on both tanks so next step is a fuel pressure regulator. You’ve made sweeping comments that are wrong and then get pissy when someone shows your wrong. Typical of today’s day and age!

 

[Orangepeel]

Once the fuel pressure regulator is replaced I’ll
report back.

 

[ripcord]

You mentioned earlier that the fuel pressure didn't rise when you disconnected the vacuum line from the regulator. This usually indicates a weak fuel pump.

I would try to verify fuel pump voltage. Also test the max fuel pump dead head pressure. It should be higher than the book pressure or you have weak pumps.

 

[OVERKILL]

so checking timing with a timing light is a blast on this truck. The timing marks aren’t there like on the older ones. That being said scan tool reports 10 degrees with spout connector unplugged. At this point I don’t think it’s ignition. The long term fuel trims make me think it’s a fuel issue or possibly air but I’m at a loss.

Scan tool has no idea what the base timing is, it just assumes it's 10 degrees. There will be marks on the balancer, you may need some sandpaper and a paint pen/whiteout to actually use the light with them though.

 

[OVERKILL]

You mentioned earlier that the fuel pressure didn't rise when you disconnected the vacuum line from the regulator. This usually indicates a weak fuel pump.

I would try to verify fuel pump voltage. Also test the max fuel pump dead head pressure. It should be higher than the book pressure or you have weak pumps.

Yes, but this could also mean that the regulator is defective. While they often leak out the vacuum port when they fail, they don't always.

 

[Orangepeel]

Yes, but this could also mean that the regulator is defective. While they often leak out the vacuum port when they fail, they don't always.

Regulator is replaced. It was or at least appeared to be original. The front fuel tank running is 30psi and doesn’t drop or rise when engine is revved.
The inconsistency of accurate information with this truck is super frustrating. Professional grade sources cannot even provide trustworthy fuel pressure info.

Motor says one thing oem says another Mitchell 1 says the same thing oem says. Frustrating!

 

[Orangepeel]

Scan tool has no idea what the base timing is, it just assumes it's 10 degrees. There will be marks on the balancer, you may need some sandpaper and a paint pen/whiteout to actually use the light with them though.

I did not see marks and I did looks quite thoroughly. I’ll check again tomorrow. That being said I read online on a ford forum that ford got away from the marks on the balancer. Whether that is true or not I am unsure. The truck ran good when I bought it and nobody has messed with the timing since I’ve had it so it is unlikely to be an issue.

 

[ripcord]

Does it run better on the other tank?

The 351w in my 96 has timing marks, btw.

 

[Orangepeel]

You mentioned earlier that the fuel pressure didn't rise when you disconnected the vacuum line from the regulator. This usually indicates a weak fuel pump.

I would try to verify fuel pump voltage. Also test the max fuel pump dead head pressure. It should be higher than the book pressure or you have weak pumps.

How would you go about checking their dead head pressure?
Also I did check the front pump wiring I have battery voltage at the red wire at the pump and 3.5 at the light blue yellow wire.
There is also a black and an orange they had no voltage. I haven’t been able to source a super great wiring diagram yet to see what all is what.
Unsure what the light blue yellow wire should have voltage wise
Or the other 2 that had no voltage for that matter.

 

[Orangepeel]

Does it run better on the other tank?

The 351w in my 96 has timing marks, btw.

I’ve seen pictures where they have the gear and you line the mark up which is pretty Standard. This truck doesn’t have that which is weird. It has a weird looking nub below the crank sensor. Maybe there is marks that I just didn’t see but the little gear looking portion is definitely not there. I’ll take pictures tomorrow.

 

[clinebarger]

You check for excess return volume if you suspect a faulty FPR causing low fuel pressure, Blocking the return will dead head the pump. You likely have zero fuel at the return!

 

[ripcord]

If you pinch off the fuel return line, you should see the maximum output pressure from the pump. You do not want to force the pump to run this way for long as it can over stress them. 10 seconds or less.

 

[Lubener]

Would you like to pay for that? The fuel pressure is low on both tanks so next step is a fuel pressure regulator. You’ve made sweeping comments that are wrong and then get pissy when someone shows your wrong. Typical of today’s day and age!

Show me that I am wrong. You post and don't comprehend or take advice well. I have been working on 4.9's for 25 years. I have the factory documentation where you have misleading internet information. Good luck with your truck....you will need it at the rate you are going.