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#4112538 - 06/15/21 02:48 PM engine running lean, both banks. No vacuum leak*
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
lean codes for 2006 p71 interceptor, bone stock.

LTFTS stay at 19-25, STFTS stay at -2-5.
LTFTS do not stabilize under engine load or during driving. only time fuel trims stabilitze at 0 is when I'm letting off throttle. As I understand vacuum leaks typically stabilize under throttle.
no drivability issues or misfires.

I've cleaned MAF and ran smoke test. on smoke test smoke only came out of my EGR diaphragm and I went ahead and replaced it. Didn't expect a fix but on follow up smoke test no smoke anywhere accept a trickle coming out of where I crudely capped the throttle body.

Fuel pressure goes from 39-44 from idle to higher engine load. This is according to scanner as my fuel rail doesn't have a schrader and I havn't got around to getting an adaptor for getting fuel pressure gauge straight into fuel line. Would bad fuel pressure sensor effect fuel pressure on scanner?

Went ahead and replaced the fuel filter and upstream 02s because they were nasty.

PCV valve good.

I don't think its IAC as car idles steady at 775-780.

at this point i'm thinking a small exhaust leak before upstream 02s as cars entire exhaust is pretty rusty looking. but if car was upping fuel to accommodate non existent unmetered air wouldn't the car drive sluggish and smokey due to access fuel in chamber?

or a bad or faulty PCM. Planning on cleaning / replacing fuel injectors and doing spark plugs soon just because.

Maybe a leak at intake gasket but wouldn't that leak smoke during test?

i'm a classic shade tree mechanic powering up the rapid fire parts cannon. any help would be appreciated.
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

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#4112548 - 06/15/21 04:20 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7613
Loc: MA
Originally Posted By ecashin90
I don't think its IAC as car idles steady at 775-780.
You can remove the IAC from the parts cannon as your car doesn't have one. They were eliminated with the switch to DBW in '05.
_________________________
'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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#4112556 - 06/15/21 04:47 PM Re: engine running lean, both banks. No vacuum leak* [Re: RF_Overlord]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
Duly noted.
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

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#4112586 - 06/15/21 08:07 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
GM_Guy Offline
Posting Addict

Registered: 12/17/00
Posts: 18600
Loc: London, Ontario Canada
Any broken exhaust manifold bolts? Do a smoke test on the exhaust system.
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#4112592 - 06/15/21 09:37 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
professorP7B Offline

Member

Registered: 04/02/20
Posts: 325
Loc: Rhode Island
Lean means one of two things: unmetered air or insufficient fuel delivery. While exhaust leaks ahead of the O2s is possible you'd likely hear them if they were severe enough to throw off an O2 (in my experience, anyway.)

I'd start by doing a volumetric efficiency test. This is good way to determine if the car is actually seeing the air coming through and whether it is able to deliver the correct amount of fuel. That link I provided is a free calculator that allows you to enter the parameters necessary to calculate VE. Just input the engine size (4.6 in the case of a Panther,) number of cylinders (8, obviously,) and the barometric pressure for the day (can be found on pretty much any weather app.)

For the MAF, RPM and IAT (intake air temp,) do a full-throttle 1st gear pull and enter each of those parameters as they appear just before the 2nd gear shift. Many scanners can record the highest range a value hits.

At the top of the link page is a button that says "Show VE Calculator Instructions" and it does a spectacular job of how to interpret the results, so I won't bother going into crazy detail here. But suffice to say, a VE test can actually be a valuable data point in your diagnosis. Don't fire the parts cannon, please...
_________________________
Teacher/Technician. 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.
The garage queen...
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5.3L LC9 V8 4X4 Ext. Cab
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#4112642 - 06/16/21 02:06 PM Re: engine running lean, both banks. No vacuum leak* [Re: professorP7B]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
Will do.

As regards to exhaust leak, I feel like I can hear a small one under certain throttle when I'm just listening to the engine, but that may just be the sound of this motor. Did a test of the exhaust by way of putting a cleaned out shop vac exhuast into one of the tail pipes, turning it on, and spraying every bit of exhuast from rear all the way up to manifolds very soapy water mixture. no bubbles anywhere. did a second more crude test where I 'soft' plugged the exhaust with clean shop rags to deafen the exhaust acoustics but couldn't hear exhaust anywhere else. I never trust a test done once so I'll do these again.

also if a possible leak is pre 02, the 02s aren't detecting anything. once engine balances out the lean condition the upstream 02 fuel trims on scanner are showing good. I guess this is either the engine correctly accommodating the lean condition or lean condition is being falsely corrected and 02 fuel trims are being determined with a possible pre 02 leak. I doubt this as the behavior of the trims is almost perfectly mirrored between bank 1 and 2.

I think its a fuel issue somewhere as fuel trims don't behave like a vacuum leak and I occasionally hear engine pinging noise which, if I understand right, sometimes points to bad injectors. what's frustrating is I have suffered 0 drivability issues. car pulls strong and hasn't bogged down y e t


Thanks for the help so far!
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

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#4112736 - 06/17/21 10:47 AM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
VE results @4750 RPM
12.4 lb/min MAF
77 F IAT
8 cylinders
14 in/hg as per MAP

EST_VE = 92.94%

so no or very minor vacuum leak ?

Connected my scanner to its bluetooth app and it ran its little analyzer based on the freeze frame data of the lean code . Scanner app tells me to replace MAF. my local store has a hitachi MAF which looks like the motorcraft one. I read on some forum posts of the hitachi's being good to use so that's the next thing i'll do.



Edited by ecashin90 (06/17/21 10:48 AM)
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

Top
#4112758 - 06/17/21 01:26 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
RF_Overlord Offline

Poobah

Registered: 12/14/02
Posts: 7613
Loc: MA
Hitachi is the OEM for the MAFs used on the 4.6 (and others) so you heard right. Use it with confidence.
_________________________
'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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#4112770 - 06/17/21 02:21 PM Re: engine running lean, both banks. No vacuum leak* [Re: RF_Overlord]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
Good to know.
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

Top
#4112772 - 06/17/21 02:49 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
on my lunch break today I did a spray leak test with carb cleaner. Hit all the vacuum lines and the tops of the injectors and where the intake seals. No surges anywhere.

bought the car as is from a small dealer. When I first looked at the car it had the lean codes and they 'fixed it' before I bought it.
day I get home with it I realized that there was no air filter on it. Frankly I'm ashamed I missed it but w/e. Bought a filter from advance. A purolator. After my next drive with air filter in the lean codes appear
I'm not sweating the codes as I half expected them to just delete them and send me out the door. I was just thirsty for a SAP crown vic and the car is thoroughly clean.

Anyways.

Could the car having run without an air filter for however long have contaminated the MAF so thoroughly that it can't be cleaned?



Edited by ecashin90 (06/17/21 02:53 PM)
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

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#4112786 - 06/17/21 04:24 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
GM_Guy Offline
Posting Addict

Registered: 12/17/00
Posts: 18600
Loc: London, Ontario Canada
It could have contaminated, but a good cleaner should get it cleaned up. Give it another good spraying in the open air and hit it a few times just because.
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#4112798 - 06/17/21 05:59 PM Re: engine running lean, both banks. No vacuum leak* [Re: GM_Guy]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
just saw a video of a guy knocking debri out of this very same MAF. He had to strike it against a table. Will try that as well.
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

Top
#4112800 - 06/17/21 06:16 PM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
Lance01 Offline
Member

Registered: 04/02/18
Posts: 489
Loc: Pa
Running the engine without the air filter contaminates the oil with foreign dirt and particles that causes the engine to wear out more quickly. It's like adding abrasive material to the oil. Make sure the oil gets changed.

Back in the old days some drag racers use to drag race without the air filter but driving along the road without an air filter is something that just shouldn't be done.

In your situation, it's unknown how long the car was driven without an air filter but it's unlikely any damage was done to the MAF sensor directly but maybe as it is sensitive to dirt and foreign particles.


I also needed a MAF sensor and the Hitachi sensor was like 200$ and I believe it's just rebuilt not even new. So I decided to just go to the junkyard and I found a the newest p71 vic and pulled a MAF from it for only 5 bucks. I cleaned it up real good with MAF cleaner and I remember when I installed it my acceleration was more crisp and it felt as though I picked up a few ponies.


Edited by Lance01 (06/17/21 06:17 PM)

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#4112808 - 06/17/21 06:47 PM Re: engine running lean, both banks. No vacuum leak* [Re: Lance01]
ecashin90 Offline
n00b

Registered: 06/06/21
Posts: 14
Loc: Georgia
did one already. I have no idea how the car could end up driving without a filter. lol.

my advance has a hitachi for 60. I'm going to really clean mine again and see if there is any large particles in there maybe. if not that then I'm going to replace it just to eliminate it from this troubleshooting.

If issue isn't maf then I can only assume its a legitimate vacuum leak that I can't find though trims don't behave like it, or some issue with the fuel delivery or some weird electronic gremlin somewhere.


Edited by ecashin90 (06/17/21 11:46 PM)
_________________________
2006 SAP p71

1998 S10 Shortbed / standard cab / 4.3

1995 CB750 Nighthawk

Top
#4112868 - 06/18/21 03:12 AM Re: engine running lean, both banks. No vacuum leak* [Re: ecashin90]
Decimator714 Offline
Stranger

Registered: 02/04/20
Posts: 1
Loc: TX
Check your fuel injectors. Mine had sut clogged in them from a bad fuel filter. Was able to take carb cleaner to wash them out.

I had the same symptoms as you. Even did the smoke test and replaced my egr.

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