p1408 and stumbling
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Senior Member
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From: Houston
p1408 and stumbling
01 4.6 F150
The other week my truck was driving fine, then one day it just starts surging while idling and when I'd drive it and put a load on the engine it felt like a misfire and stumbling. I decided to go to my friends shop and use their IDS and after doing a koer self test, it came back with a P1408. I went ahead and pulled the throttle body off and cleaned out the egr ports and that didn't fix it. I went ahead and replaced the egr solenoid and dpfe sensor and those didn't fix it. I was able to apply vacuum to the egr valve and that stopped the surging idle, and I concluded it was in working order (not sticking open and opening/closing fine). I wasn't able to pull any codes with either of my dtc readers after all that. I went ahead and finally put in my upstream o2 sensors and brand new cop's and spark plugs.
It idles smooth now, but it still feels like it's stumbling under load. I checked for vacuum leaks and i wasn't able to find any, I don't suspect it's the fuel filter as it has about 10k miles on it and it doesn't act like it's starving for fuel when I get on it.
Any thoughts or ideas?
The other week my truck was driving fine, then one day it just starts surging while idling and when I'd drive it and put a load on the engine it felt like a misfire and stumbling. I decided to go to my friends shop and use their IDS and after doing a koer self test, it came back with a P1408. I went ahead and pulled the throttle body off and cleaned out the egr ports and that didn't fix it. I went ahead and replaced the egr solenoid and dpfe sensor and those didn't fix it. I was able to apply vacuum to the egr valve and that stopped the surging idle, and I concluded it was in working order (not sticking open and opening/closing fine). I wasn't able to pull any codes with either of my dtc readers after all that. I went ahead and finally put in my upstream o2 sensors and brand new cop's and spark plugs.
It idles smooth now, but it still feels like it's stumbling under load. I checked for vacuum leaks and i wasn't able to find any, I don't suspect it's the fuel filter as it has about 10k miles on it and it doesn't act like it's starving for fuel when I get on it.
Any thoughts or ideas?
Technical Article Contributor
Joined: Oct 2005
Posts: 25,641
Likes: 19
From: MI
01 4.6 F150
The other week my truck was driving fine, then one day it just starts surging while idling and when I'd drive it and put a load on the engine it felt like a misfire and stumbling. I decided to go to my friends shop and use their IDS and after doing a koer self test, it came back with a P1408. I went ahead and pulled the throttle body off and cleaned out the egr ports and that didn't fix it. I went ahead and replaced the egr solenoid and dpfe sensor and those didn't fix it. I was able to apply vacuum to the egr valve and that stopped the surging idle, and I concluded it was in working order (not sticking open and opening/closing fine). I wasn't able to pull any codes with either of my dtc readers after all that. I went ahead and finally put in my upstream o2 sensors and brand new cop's and spark plugs.
It idles smooth now, but it still feels like it's stumbling under load. I checked for vacuum leaks and i wasn't able to find any, I don't suspect it's the fuel filter as it has about 10k miles on it and it doesn't act like it's starving for fuel when I get on it.
Any thoughts or ideas?
The other week my truck was driving fine, then one day it just starts surging while idling and when I'd drive it and put a load on the engine it felt like a misfire and stumbling. I decided to go to my friends shop and use their IDS and after doing a koer self test, it came back with a P1408. I went ahead and pulled the throttle body off and cleaned out the egr ports and that didn't fix it. I went ahead and replaced the egr solenoid and dpfe sensor and those didn't fix it. I was able to apply vacuum to the egr valve and that stopped the surging idle, and I concluded it was in working order (not sticking open and opening/closing fine). I wasn't able to pull any codes with either of my dtc readers after all that. I went ahead and finally put in my upstream o2 sensors and brand new cop's and spark plugs.
It idles smooth now, but it still feels like it's stumbling under load. I checked for vacuum leaks and i wasn't able to find any, I don't suspect it's the fuel filter as it has about 10k miles on it and it doesn't act like it's starving for fuel when I get on it.
Any thoughts or ideas?
In bold. - Yea, that doesn't make sense. "Applying Vac" - It will (should) stumble and almost stall IF, -the valve is functioning properly.
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Senior Member
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From: Houston
Yeah, it does stumble when i applied vacuum to the egr valve at idle, but driving it feels just like i opened the egr valve when i give it throttle.
Technical Article Contributor
Joined: Oct 2005
Posts: 25,641
Likes: 19
From: MI
Just pull the green line and take it for a ride. That will eliminate a EGR valve and vac problem.
10,000 miles on the fuel filter is more than I like. I change them every 9,000. A bad ff won't always act as tho you are running out of fuel, not always anyway.
Usually, if it's a coil, it will act up under normal acceleration load and once it hits OD.
No CEL, - try to initiate. Hold at stumble to increase misfire count. The comp may pickup the problem.
Check the usual suspects, compression test last.
10,000 miles on the fuel filter is more than I like. I change them every 9,000. A bad ff won't always act as tho you are running out of fuel, not always anyway.
Usually, if it's a coil, it will act up under normal acceleration load and once it hits OD.
No CEL, - try to initiate. Hold at stumble to increase misfire count. The comp may pickup the problem.
Check the usual suspects, compression test last.
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From: Houston
Just got back from my friends shop and the almighty IDS
Cylinder 4 misfire is the culprit
I did koer tests, network tests and relative compression test all passed, and i was happy to see my compression test was in spec, only 2 & 5 were down just by a single bar (well within fords spec 10-15%)
Once the engine cools and I can find a good coil I'll report back with the results
Cylinder 4 misfire is the culprit
I did koer tests, network tests and relative compression test all passed, and i was happy to see my compression test was in spec, only 2 & 5 were down just by a single bar (well within fords spec 10-15%)
Once the engine cools and I can find a good coil I'll report back with the results