After fuel fill up

jc8828

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Anyone had issues with erratic RPM fluctuation and sometimes even going dead after filling up with gas? It does this every time I fill up. Car will idle as normal and then about 20-30 seconds after cranking the engine will idle roughly and the rpm will drop to almost shutting the car off then go back to normal and does this for about a minute. Sometimes it even shuts off. If it does not die, it does that for about a minute or so then it goes away and never does it until next time I put in gas. It has done this since I have owned the car (almost a year) and I know the previous owner and he said it did that to him for as long has he owned the car (2 years). I always use the highest octane gas.

2008 Roush 427R 4.6 3v
 

Heaten m90

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Interesting, im unsure why filling the fuel tank would effect the car. Mybe change the fuel filter, clean the TB, relearn the TB and clean the MAFs. Any diagnostic codes? Maybe the crossover tube??? Idk man
 

skwerl

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My first guess would be the vent hose is clogged up. Do you 'top it off' after the pump shuts off? If so, then stop. No, you don't need to round it off to the next dollar. When it shuts off, remove the nozzle and hang it up. Period. Do that for 3-4 fillups and see if it stops.
 

86GT351

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Get the car scanned and see if there are any stored codes. Not uncommon for a vapor management Valve to stick. Causes what you are experiencing.
 

jc8828

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My first guess would be the vent hose is clogged up. Do you 'top it off' after the pump shuts off? If so, then stop. No, you don't need to round it off to the next dollar. When it shuts off, remove the nozzle and hang it up. Period. Do that for 3-4 fillups and see if it stops.

I do remove the nozzle after it shuts off. Thanks for the suggestion to check vent hose.
 

jc8828

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Get the car scanned and see if there are any stored codes. Not uncommon for a vapor management Valve to stick. Causes what you are experiencing.

I'll try that. It is very odd that once it does it that one cycle, it just clears up and no issues until next fill up.

I even tried just putting just $10.00 (not all the way fill up), but it did it then also. Not a big issue, just annoying!!
 

06JET

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I would try the fuel cap. Take it off and just put it back on and see if that does it. Do it multiple times starting you car after each as if you put gas in it and see what happens.
 

jc8828

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I would try the fuel cap. Take it off and just put it back on and see if that does it. Do it multiple times starting you car after each as if you put gas in it and see what happens.

Interesting theory!! I'll try that.
 

86GT351

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I'll try that. It is very odd that once it does it that one cycle, it just clears up and no issues until next fill up.

I even tried just putting just $10.00 (not all the way fill up), but it did it then also. Not a big issue, just annoying!!

Not really. When full the valve recognizes more vapor pressure and can amplify the situation.
 

slow06stang

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I have never dug into the vapor stuff on these cars. I know on my Sport Trac, it had issues with not wanting to accept fuel, and low idle, surging, and long cranks. I cleaned the vent hose. It did get a little better. So I replaced the vapor canister, and it has done fine ever since. I took the old one apart and it was like a plastic filter that looked like a brick of mud.
 

86GT351

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I have never dug into the vapor stuff on these cars. I know on my Sport Trac, it had issues with not wanting to accept fuel, and low idle, surging, and long cranks. I cleaned the vent hose. It did get a little better. So I replaced the vapor canister, and it has done fine ever since. I took the old one apart and it was like a plastic filter that looked like a brick of mud.

Vapor Canister is also a key item. When you put gas in and the pump shuts off pull the nozzle out and you are done. If you try and top it off the excess fuel goes down the vapor hose in to the canister. Once the Canister gets saturated it can not do its job properly.
 

jc8828

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Any updates? Really curious as to the cause.

Hopefully will try some of the recommendations this weekend. I keep my car in spare bay of brothers garage and not had any time to test theories or any codes. Getting it out this weekend after all this rain from Hurricane Irma goes away.
 

JeremyH

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I also agree sounds like a vent/evap issue from pressure that builds up when you fill, that's the only thing I can think of.
 

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