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#4077210 - 09/10/20 09:02 AM Possible Fuel/Air mixture problem
DonnieK Offline
Stranger

Registered: 01/15/20
Posts: 6
Loc: Nashville, TN
2005 CVPI here, 130k miles, mostly original... Kinda long story ahead, but trying to give full context.

So I searched through the topics and found a couple possible related, but ive got a combo of things happening.

I noticed a few months ago that the car would run slightly rough immediately after fill up. Many people report having problems STARTING, but mine would crank immediately, and then run rough for about 5 min before everything was fine. Didnt think much of it, ran some sea foam through for possibly some gunk in there. Also, I do 90% interstate driving in this car. 350 miles at a time.

So, about 3 weeks ago, I filled up in the city and was driving around and the thing started running VERY rough and died at several traffic lights. When I pushed down the accelerator, the engine would die, almost like it was choking out. Even got a backfire like there was a really bad misfire. Drove home and the the next day the car ran fine again, like nothing was the matter.

Yesterday, after the car had been sitting for about 4 days, I got in, and started down the interstate. After about 20 minutes, the engine just slowly choked out, and if I pushed the accelerator, it would actually lose RPM. So, after reading some of the forums, I checked a few things and nothing worked. Well, I ended up removing the gas cap and the car started right up. I put it in drive and proceeded to drive 180 miles without issue. Oh, I should also say the car had approx half a tank of fuel with the recent issue. So, I needed gas to get home, so I stopped and filled the tank, but didnt shut the engine down. It never even burped. Ran like a top all the way home.

So I deduced that I potentially had a bad gas cap. So, I drove to the gas station, filled up, then across the street to oriellys to get a new gas cap. Put the new cap on and not only ran rough this time, but threw a check engine light. 02 upstream sensor. ALso cyld5 misfire. So, took the cap off and was able to limp the car home.

Im at a loss here, without replacing basically all my air sensors, etc etc. Full blown tune up maybe, I guess its probably about time for that anyway. But does anyone have a guess on what might be going on here. Its like the engine is starving for air. But the fact that it starts right up is what is baffling me here.

Thanks for reading, if youve gotten this far.
_________________________
2005 CVPI, Street Appearance Package. Former Detective car from Small town TN.

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#4077214 - 09/10/20 11:28 AM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
professorP7B Offline
Member

Registered: 04/02/20
Posts: 179
Loc: Massachusetts
Sounds like an EVAP vent valve or plumbing issue. As the engine runs and the fuel pump pumps fuel from the tank, air needs to enter through the EVAP vent to fill in the space left behind in the tank as the level drops. If it can't get in, a vacuum is pulled on the tank to the point that the pump can't pull fuel anymore.

An EVAP canister that is flooded with fuel will also cause this issue. "Topping off" (continuously clicking the gas nozzle after it clicks off) will easily cause this problem.

Removing the gas cap prevents a vacuum from being pulled on the system, hence "correcting" the issue. The upstream O2 code and Cyl.5 misfire are probably just a result of the engine going lean due to fuel starvation when the issue occurs.

I would start by checking the vent line from the canister. On my '11 anyways, the line comes off the right side of the canister (which is bolted to the trunk pan, under the car) and snakes up into the passenger side frame rail. Make sure this hose isn't blocked.
_________________________
Former Toyota tech. First-time Ford owner. ASE-certified Advanced Level Specialist.
Current vehicles:
2011 Crown Vic P7B (SAP, former campus police vehicle)
Purchased 3/27/20 w/51K, 819 idle hrs.
Approaching obnoxious number of mods for sig...
2011 GMC Sierra 1500 SLE
Purchased 2/23/17 w/57K
5.3L LC9 V8 4X4 Ext. Cab
My sig would be obnoxiously long if I listed the mods on this one...
2007 Mitsubishi Galant ES-AKA "Oreo"
Purchased 6/5/17, sold 10/12/17, given back to me 5/26/20
Factory rot, aftermarket duct tape, high performance zip ties.

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#4077230 - 09/10/20 03:10 PM Re: Possible Fuel/Air mixture problem [Re: professorP7B]
DonnieK Offline
Stranger

Registered: 01/15/20
Posts: 6
Loc: Nashville, TN
Good stuff! I read a similar issue with a similar fix. I'm gonna give it a shot and ill report back.
_________________________
2005 CVPI, Street Appearance Package. Former Detective car from Small town TN.

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#4077236 - 09/10/20 05:25 PM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
Lance01 Offline
Member

Registered: 04/02/18
Posts: 357
Loc: Pa
Check all your rubber vacuum hoses. I had numerous cracks in various hoses so I went to the junkyard and got a handful of hoses off newer Fords. Went to the counter to pay and they let me have em all for free. My car now runs just a tad bit better now and no more hissing sounds from the PVC plumbing area.

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#4077312 - 09/11/20 01:42 PM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7180
Loc: MA
I second everything professorP7B said.

In addition, check the CVS (Canister Vent Solenoid) in the same tray as the charcoal canister, It should be normally open to allow fuel to be pulled from the tank (as professor explained). If it's clogged or defective/stuck shut, you'll have that vacuum condition he described.
_________________________
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen

'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)

'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember
Being resurrected...slowly.

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#4077764 - 09/15/20 04:40 PM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
DonnieK Offline
Stranger

Registered: 01/15/20
Posts: 6
Loc: Nashville, TN
Ok, checked those lines, no apparent blockages. Put on a new fuel cap and once the car was cold, everything runs fine. But once the car gets warm, and then shut the engine off, re-start is fine, but runs rough and replicates issue. Took the cap off and still doesnt run very well. Took me about 20 minutes in the parking lot at lunch to get it where it would run good enough to drive.

Same problem, runs rough and when you push the accelerator pedal, it sounds like the engine is being choked out. So, under the hood, at the evap purge solenoid, I took on of the vacuum hoses off and it was sucking really good air. When I plugged it with my finger, the engine instantly died.

Amateur assessment here, but could that mean the purge solenoid is fine and doing what its supposed to and perhaps my issue with the evap canister valve, or the canister itself?
_________________________
2005 CVPI, Street Appearance Package. Former Detective car from Small town TN.

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#4077774 - 09/15/20 07:02 PM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
professorP7B Offline
Member

Registered: 04/02/20
Posts: 179
Loc: Massachusetts
If I'm understanding you correctly, you pulled the supply line to the purge solenoid and felt vacuum, plugged the end of the supply line with your finger and then the engine died? If you pulled the hose from the solenoid down to the canister and you felt vacuum it was either in a purge cycle when you checked it or the purge valve is bad.

With the purge solenoid completely disconnected from all hoses and wires, try blowing through it; you shouldn't be able to. If you can blow air through it while it is unplugged/disconnected, it's stuck open. This could certainly cause a lean condition, and if left long enough fuel trims might be so rich that once the vacuum leak was plugged up (via your finger blocking the purge supply line) it just choked out with fuel.

I'm spit-balling a bit here based on what I'm reading so far. But what I've described above might also explain why messing with the fuel cap seems to have some effect on the running condition.

I know these engines are also seriously prone to intake problems, but haven't dealt with one personally. I'm sure others could chime in on that possibility.
_________________________
Former Toyota tech. First-time Ford owner. ASE-certified Advanced Level Specialist.
Current vehicles:
2011 Crown Vic P7B (SAP, former campus police vehicle)
Purchased 3/27/20 w/51K, 819 idle hrs.
Approaching obnoxious number of mods for sig...
2011 GMC Sierra 1500 SLE
Purchased 2/23/17 w/57K
5.3L LC9 V8 4X4 Ext. Cab
My sig would be obnoxiously long if I listed the mods on this one...
2007 Mitsubishi Galant ES-AKA "Oreo"
Purchased 6/5/17, sold 10/12/17, given back to me 5/26/20
Factory rot, aftermarket duct tape, high performance zip ties.

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#4077824 - 09/15/20 09:29 PM Re: Possible Fuel/Air mixture problem [Re: professorP7B]
DonnieK Offline
Stranger

Registered: 01/15/20
Posts: 6
Loc: Nashville, TN
It wasnt the line from the tank, but rather the line from the solenoid to the intake manifold. I pulled it off and was unable to blow through it. It runs a purge when the car is cold, correct? The car was very warm when I plugged the hose and made it stall out. It doesnt seem like there is a vacuum leak, but is it possible that the leak is so subtle, its hard to detect?
_________________________
2005 CVPI, Street Appearance Package. Former Detective car from Small town TN.

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#4077874 - 09/16/20 12:21 AM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7180
Loc: MA
Originally Posted By DonnieK
So, under the hood, at the evap purge solenoid, I took on of the vacuum hoses off and it was sucking really good air. When I plugged it with my finger, the engine instantly died.
That's the opposite of what should have happened. The Vacuum Management Valve (a.k.a. the purge valve) is normally closed, so removing the line going to the intake should have caused a massive vacuum leak. When you put your finger over the end, you were simply restoring it to normal.

Originally Posted By DonnieK
could that mean the purge solenoid is fine and doing what its supposed to and perhaps my issue with the evap canister valve, or the canister itself?
That's what it sounds like to me...
_________________________
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen

'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)

'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember
Being resurrected...slowly.

Top
#4078016 - 09/17/20 09:01 AM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
DonnieK Offline
Stranger

Registered: 01/15/20
Posts: 6
Loc: Nashville, TN
Ok, update. I checked the purge solenoid and it "SEEMED" to be working fine. I couldnt blow any air through it. Also, I removed and cleaned the canister valve on the back of the car. It clicked, when my wife turned the car on, (I could feel it while I held it in my hand). So.. both seemed to be working. I know this isnt precise, so I still had my doubt.

Upon reading more on symptoms, I finally decided, I wasnt having problems fueling the car, and also when the car was cold. So, I decided to goto my local pull-a-part and I got a new purge solenoid. I thought maybe that dude is staying closed all the time, causing the engine to starve. So, I reset the check engine light, put the new solenoid on and it seems to be running fine now. I took it down the road and got it warm, then shut it down for about 30 minutes, and it fired right back up just fine. Still hasnt kicked a code back out. So, fingers crossed that may have fixed it. Im going to go and fill the tank again, because now, the gas needle has moved off FULL, so I want to see if that causes the problem again.

I'll report back. Thanks for the info so far.
_________________________
2005 CVPI, Street Appearance Package. Former Detective car from Small town TN.

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#4078054 - 09/17/20 05:31 PM Re: Possible Fuel/Air mixture problem [Re: DonnieK]
DonnieK Offline
Stranger

Registered: 01/15/20
Posts: 6
Loc: Nashville, TN
Additionally, I filled the car tank up today after driving and had no issues.

Seems like I may have resolved the issue. Thanks for the info. The new purge solenoid fixed it up.
_________________________
2005 CVPI, Street Appearance Package. Former Detective car from Small town TN.

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