Bad Fuel Pressure Regulator? - TCCoA Forums
 
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post #1 of 17 (permalink) Old 12-16-2016, 05:38 PM Thread Starter
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Bad Fuel Pressure Regulator? P0712 & P0175

I've been getting a CEL for rich on both banks, and the car idles a little rough and will stutter badly when first trying to accelerate until the motor is warmed up. I also have been getting terrible fuel mileage (13mpg). I checked the fuel pressure at idle tonight and got the following numbers:

With Vac Line 34
Without Vac Line 42

Those seem in range with what it should be, however when I moved the throttle the pressure moved right along with it. My understanding is that this should only be happening 1:1 during boost, not all the time with the throttle. Is that correct, or is a movement with any throttle normal?

Thomas

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-

Last edited by Thomas A; 12-21-2016 at 09:27 PM.
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post #2 of 17 (permalink) Old 12-16-2016, 07:21 PM
No, Mr. Lemmywinks, No!!!

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The object of the regulator is to keep the pressure across the injector at a constant value; so it should track manifold pressure, psi/psi.

IDK about specific ratios, or pressures, or anything; but it should move together.

And yes, at 22psi of boost, you need 62 psi for a 40 psi drop.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


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post #3 of 17 (permalink) Old 12-16-2016, 07:32 PM Thread Starter
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So if I am not in boost, the pressure should remain consistent, regardless of throttle movement or position (until I get into boost).

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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post #4 of 17 (permalink) Old 12-16-2016, 07:54 PM
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The pressure should change with vacuum or boost. You would need to see what the manifold pressure was doing to correlate the fuel pressure.

Basically the fuel pressure will rise from full vacuum to full boost. If you have 14 inches of vacuum, that's about 7 psi. So if your regulator is set for 42 psi, you would see around 35 psi at full vacuum. The fuel pressure would rise as vacuum decreases and boost begins. Once you are into boost, the pressure should rise 1:1. So at 14 psi boost you should see 56 psi fuel pressure.
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post #5 of 17 (permalink) Old 12-17-2016, 04:18 PM Thread Starter
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Thanks guys, that makes sense. Well, it seems that the regulator is at least functioning, and the readings seems reasonable. It would be best if I had a longer hose so I could watch the gauge while driving, but I don't.

Any ideas what could be causing such a rich condition? My next thought was an issue with the MAF. It is nice and clean, and the connection seems good. I unplugged it while running to see if it made a difference and it certainly did (idled poorly and almost died), so it does seem to be doing something.

Here are the codes:
P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0172 System too Rich (Bank 1)
P0175 System too Rich (Bank 2)

I can monitor and log some basic PIDs through my scan tool, but I don't have a XCAL or something like that to do detailed data logging.

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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post #6 of 17 (permalink) Old 12-17-2016, 06:28 PM
No, Mr. Lemmywinks, No!!!

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Quote:
Originally Posted by Thomas A View Post
Here are the codes:
P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0172 System too Rich (Bank 1)
P0175 System too Rich (Bank 2)

I can monitor and log some basic PIDs through my scan tool, but I don't have a XCAL or something like that to do detailed data logging.

Change both of the O2 sensors on that side; the rear one is bad, and pulling down the whole system.

I had a rough time diagnosing this a few years ago, days after seafoaming a very dirty engine on the Red Cougar.

I usually move the front sensor to the rear and buy a new front one, but in this case that did not work, and still gave occasional rich errors.
Replacing the rear one fixed it.

I had the same prob on the other side about 3 months later, when it turned cold.


If they're all the same age, well, it's time to do all 4.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #7 of 17 (permalink) Old 12-17-2016, 07:38 PM Thread Starter
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The front two are new, and the rears are lower mileage (swapped to back like you did). The one isn't reading any voltage on my scan tool (wiring looked fine), so perhaps it is bad. I didn't think the rear ones did much of anything other than check the efficiency of the catalyst system? Seems many guys have them turned off when they have the car tuned?

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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post #8 of 17 (permalink) Old 12-17-2016, 08:03 PM
No, Mr. Lemmywinks, No!!!

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They're apparently used for something; but if they short, they make the front ones read off too.

Even if they're turned off in the tune, so it's something real happening to the sensor.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #9 of 17 (permalink) Old 12-17-2016, 09:19 PM Thread Starter
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I'll give it a try; Replacement O2 should be here later this week; I'll get it swapped in and see what happens. Is Bank1 the drivers side or passenger side?

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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post #10 of 17 (permalink) Old 12-18-2016, 01:25 AM
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Bank1 is the side the #1 cylinder is on.

RwP

Fuelly
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post #11 of 17 (permalink) Old 12-18-2016, 03:34 PM
No, Mr. Lemmywinks, No!!!

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Oh I forgot, you can just unplug it if it's turned off in the tune.

Even if it's not, it won't pull down the front one; you'll just get the catalyst efficiency error. (iirc)

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #12 of 17 (permalink) Old 12-21-2016, 09:16 PM Thread Starter
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Update:

I tried a few more things tonight. First, I found a massive vacuum leak. I can't believe I overlooked this prior, but the intake tube was not cleanly seated to the throttle body (its an aftermarket "piece)". I fixed that and cleaned the MAF while it was apart. While it helped the idle and cold stumble, it didn't solve the larger issue.

I swapped out the 02 sensor that was causing the P0136 code. I am still not getting any voltage reading out of it, and the code came back. I am going to assume there is a problem with the harness? The prior owner did replace the TC, so the transmission has been out of the car or at least moved, so I guess its possible they pinched a wire.

P0172 and P0175 quickly returned. Is it reasonable that both banks would be rich due to one downstream 02 not having a reading? It seems like more than an 02 issue at this point.

I monitored the fuel trim readings, and they seem off to me, but I really don't know what "normal" adjustments are. The Short Term % on either bank at cold idle was around -13 or so; they improved a bit once warmed up, but still ranged anywhere from -1 to -9 and bounced between that range continually. While driving, they were all over the place, anywhere from -28 to +41 (WOT run). At one point during normal driving they bounced from the - single digits up to about +20 and flat lined there for a 5 seconds or so, before dropping back down to the negative side. It just doesn't seem like normal behavior to me.

The Long Term Fuel Trim once warmed up was fairly consistent at -20% on both banks. That seems like a lot of compensation for me, but again, I don't claim to full understand how this all works.

EDIT: I read this article and it explains this fairly well, yet leaves me without a solution. So the LTFT being at -20% on both sides confirms a legitimate, ongoing rich condition. Also (according to this article), the downstream 02 sensors don't play a role in fuel trim adjustments, so the P0136 seems to be isolated to itself. In addition, a vacuum leak would cause a lean condition, not a rich one, so while it is good to fix the vacuum leak, it likely wasn't causing this problem.

Going through his basic troubleshooting list:

Ignition System Issues
BAD spark plugs - New within last 500 miles
BAD spark plug wires (4.6L equipped with coil packs) - New within last 500 miles
BAD coil pack (4.6L equipped with coil packs) - Do these ever actually go bad?
BAD spark plug boots - New within last 500 miles
BAD Coil-on-Plug (COP) ignition coils - Doesn't Apply

Fuel System Issues

Dirty or Clogged Fuel Injector(s) - maybe, but on both banks?
Leaking fuel injector - maybe, but on both banks?
Leaking fuel pressure regulator - Pressure didn't seem to bleed down much at all?
Failed pressure regulator causing excessive fuel pressure. - Readings within reasonable range

Air Filter Assembly Issues
If the air filter canister assembly has been replaced - Factory Box
Air filter canister is not latched correctly. - Latched Tightly
Air filter canister has missing pieces. - No
Wrong air filter has been installed - K&N Panel for this Application

Cooling System Issues
The thermostat is missing - No
Incorrect temperature thermostat is being used - 180* Thermostat accounted for in tune; PID shows 190* actual operating temperature
engine coolant temperature (ECT) sensor is not reporting the correct temperature. - Reads a constant 190* once up to temp


I guess I'll test my MAF next. It seems to be getting voltage as I can watch the lb/hr reading on my scan tool, but I can't view voltage with it, so I'll break out the multi-meter tomorrow and see what I come up with.

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-

Last edited by Thomas A; 12-21-2016 at 11:02 PM.
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post #13 of 17 (permalink) Old 12-22-2016, 08:35 AM
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I am surprised no one has mentioned the PCM, since it's a known fact that 97 PCM's are garbage. Any codes like that, automatically swap in a different PCM. You really think both o2's went bad at the same time?

Really pains me to say that since I have a 97.

Al

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Previous Fords:
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post #14 of 17 (permalink) Old 12-22-2016, 09:14 AM Thread Starter
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I had thought about a PCM issue as well, but thought I would test out the other mechanical parts that are easier to diagnosis. I agree though, it certainly could be a faulty circuit.

The 02 sensors are actually working very well, and doing what they should as I understand it. They are very responsive and the PCM is adjusting based off of what they are seeing. There hasn't been any codes come up for the the upstream 02's. It seems that something is causing the PCM to add too much fuel, and the 02's are picking up on that. I am going to test voltage on the MAF tonight.

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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post #15 of 17 (permalink) Old 12-22-2016, 02:43 PM
No, Mr. Lemmywinks, No!!!

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97 eecs hang injectors like the early ones do.

I had a bad fte1 from a 97; I'm using mbe2's from 96 cougars, haven't had one of those fail yet.

Check for pinched wires; the rear injector shorting Will affect the front one.

It's probably melted to the pipe; no-one seems to reroute those properly after tranny work.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #16 of 17 (permalink) Old 12-23-2016, 10:14 AM Thread Starter
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All 02 sensors are now working and reading voltage as they should. It looks like the rich condition is a result of the tune that is in the car, and not a mechanical issue. I'll work with my tuner to get that cleaned up. The good news is that I learned a lot and found and fixed two huge vacuum leaks in the process. I guess that is progress anyway

1989 Cougar XR7 - 13.21 @ 102.29 -SOLD-
1993 Thunderbird SC -Awaiting Suspension-
1994 Mark VIII - 14.85 @ 93.95 -SOLD-
1996 Thunderbird Sport 15.57 @ 89.42 -Retired @ 258k-
1997 Thunderbird LX AED -SOLD-
1997 Thunderbird Sport 15.71 @ 86.89 -SOLD-
1997 Mark VIII LSC 12.97 @ 112.15 -SOLD-
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post #17 of 17 (permalink) Old 12-23-2016, 11:05 AM
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Quote:
Originally Posted by Thomas A View Post
I guess that is progress anyway


Joe

It's not a 97 Sport, it just looks like one!

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