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Discussion Starter #1
I have a 2006 Crown Vic P71. Bought it a couple of years ago...

The car was starting to show symptoms of the need for a tune up, little harder start than normal, slightly lower gas mileage, seemed like a loss of power. Also, the car had a slight rumble at about 35 miles an hour when just cruising and barely on the gas. For a while, I thought it may be the torque converter but realized it was more like a misfire. I attribited it to the need for a tune up. Finally, the car had a "small emissions leak" code along with the "check fuel cap" light on as well.

I narrowed the CEL/Fuel cap lights and code down to what I hope to have been caused by the evap canister vapor solenoid. I bought a new one of those along with a new set of spark plugs.

I hadnt had time over the last few weeks to put these parts in but in the meantime, the car started to randomly stall when stopped in D. It starts right up after the stall. The rumble had grown worse as well.

This weekend, I changed the plugs and vapor solenoid. So far, no CEL but the car is still rumbling as described above and stalling when stopped in D.

My research has shown multiple reasons that this can occur and as usual when searching the interwebz, most of the advice was to start replacing parts. I want to avoid that if I can.

My first indication is that its a Coil Over Plug issue, but I prefer not to throw money at a new set of those if I there are other causes that I should explore first. I have considered buying one or two and eliminating the others by swapping and test driving.

I havent done anything other than the repairs above. I could get some MAF cleaner and clean the MAF (couldnt hurt right?). I have also read various sensors etc can cause this. Again, no CEL is on at this time...

Any thoughts on where to start?

Thanks in advance :beer
 

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If your COPs are original they might very well be on their way out. Check their resistance. If one or two of them are way out of whack of the others then it's a good place to start.
 

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House of Windsor 4ever!
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High run time COPs, water intrusion into the spark plug holes and plug thread corrosion can contribute to misfire, but until the CEL begins to actually flash, you have no misfire codes to start on diagnosis. As for the rumbling and stall, did you shift to neutral during braking to see if the engine keeps running? if it does, I'd say it's the TCC having some problems (possible slipping when engaged and lack of disengagement when brake pedal's pressed). Do check that the computer receives the BOO signal when the pedal's pressed; otherwise, the TCC solenoid won't disengage.
 

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Discussion Starter #4
Thanks fellas.

If your COPs are original they might very well be on their way out. Check their resistance. If one or two of them are way out of whack of the others then it's a good place to start.
Yeah, I one of the top procedures I am looking to do is to test COPs resistance. I found this info on crownvic.net:

Using a multi-meter, Select Ohms resistance.

Place one probe in the spring end,Now place the other probe between the side of the clip on top and either pin.

Wait a second for meter to read.

5.00 ohms is GREAT!
5-5.30 is ok
5.30-5.50 is suspect
Anything 5.50 or above is considered dead and needs replacing

5.60 or more IS your misfire.


Does that sound about right? Leave the spring in, probe against the spring, the other in coil to harness connector? Harness unplugged I am assuming...

High run time COPs, water intrusion into the spark plug holes and plug thread corrosion can contribute to misfire, but until the CEL begins to actually flash, you have no misfire codes to start on diagnosis. As for the rumbling and stall, did you shift to neutral during braking to see if the engine keeps running? if it does, I'd say it's the TCC having some problems (possible slipping when engaged and lack of disengagement when brake pedal's pressed). Do check that the computer receives the BOO signal when the pedal's pressed; otherwise, the TCC solenoid won't disengage.
Right, no current codes. The car stalled a couple of times since the vapor solenoid replacement and CEL reset. It still has the "rumble" as well but no CEL coming on, which is making me question if its a misfire. When I changed the plugs, there was not any visible moisture, but 6 had some oil in the well. Cleaned it up and replaced with the new plug.

I have shifted into neutral during braking and it acts better, but a few times it stumbled and almost died. Then revved up and idled. I haven't driven a lot since the plug change. I will test it a few more times by going into N while stopped and confirm I wasnt just being overly sensitive to the cars behavior.

Its random as well. Sometimes I can remain in D while stopped for as long as I want and it wont die, other times, I stop for 30 seconds and it dies. However, in either situation, it seems to idle a little bit rough.

The BOO signal - Checked by staying on the gas and very lightly touching the brakes and seeing if the engine revs a 200-300 on the tach right? Problem is, I dont have a tach. I will try it and see if I can hear it...

This "rumble" feel isnt like I am running over a rumble strip. Its slower than that. It also happens whether I have OD on or off, and it goes away if the car shifts down and has a little more torque/power being applied... Like if I am going up a slight incline at about 35, and the incline gets a little steeper, it will shift down and the rumble goes away. Higher rev type of situation...

So list so far:

BOO test
Test multiple times the cars behavior while stopped in neutral
Test COPs resistance


Thanks again!
 

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House of Windsor 4ever!
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With the amplifying info, Shane, I think you might have an IAC problem. But Steve is right in having a scantool with live data capability would help. And don't forget, just because you don't have an active CEL doesn't mean you don't have stored codes.
 

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Roller rockers are gay
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Did 06 still have the stupid intake that cracks? That's probably where I'd look for some vacuum leaks.

It's amazing what kind of stupid crap happens because of a simple vacuum leak.
 

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Using a vacuum gauge can also tell you a lot about whats going on in a engine.
 

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House of Windsor 4ever!
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It's an '06, which should be throttle-by-wire; no IAC.
Oh, I thought that happened in '08. Well, then, he will need a scan tool, because he needs to read the APP and TP sensors for any anomalies.
 

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Did 06 still have the stupid intake that cracks? That's probably where I'd look for some vacuum leaks.

It's amazing what kind of stupid crap happens because of a simple vacuum leak.
They fixed that starting in MY2002. The affected years of the cheap plastic intake manifold constantly cracking were 1996-2001.
 

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Discussion Starter #10
Thanks again for the replies so far...


EFIs don't need tune-ups. They need maintenance, and when there's a symptom, they need diagnosis & repair. Have you followed the maintenance schedule in the owner's manual?

To be honest, I havent. I bought it, checked fluids, did an oil change, ran some seafoam, changed the air filter and drove it. I am now working on performing the more serious maintenance on it.

It's coil-ON-plug, and the only possible issues are 1) failed coil, 2) failed connection, or 3) failed plug. Did you pull any of the coil boots off & inspect the springs?

I did. No cracked or torn boots and springs all looked "good" visually. By that I mean, no obvious issues with the springs.

Yes, it certainly can, and usually DOES. I recommend leaving the MAF alone unless you have a specific reason to mess with it. Guessing that it might be the cause of a particular symptom isn't specific.

I am cool leaving the MAF alone. I have never liked the idea of messing with them and thats one of the reasons I havent yet.

Get a scanner with live-data capability. I recommend the one linked in this caption:
http://www.supermotors.net/registry/media/738423


I will pick up a scanner this weekend and see if they have the one you suggested. Then I will will work on the test in your link...

Try the test described in this caption:
http://www.supermotors.net/registry/media/202695


And don't forget, just because you don't have an active CEL doesn't mean you don't have stored codes.
True!

It's amazing what kind of stupid crap happens because of a simple vacuum leak.
I have a vacuum gauge. I can add that to the list of procedures for the weekend.

So, priority 1 then is to get the scanner and perform the test. Priority 2 (1 doesnt turn anything up) is to check the vacuum. I will keep my fingers crossed for some sunshine so I dont have to do this in the rain!
 

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Probably has 190k on original plugs, with dry rotted boots and cracked coils. Change the plugs and look over the coils, boots, and springs. If they have rust, corrosion, dry rot, or cracks replace them. $38 shipped for new coils and boots off ebay. Motorcraft plugs ebay or rockauto. FOLLOW THE TSB ON THE PLUG TORQUE SPECS
 

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Discussion Starter #12
Probably has 190k on original plugs, with dry rotted boots and cracked coils. Change the plugs and look over the coils, boots, and springs. If they have rust, corrosion, dry rot, or cracks replace them. $38 shipped for new coils and boots off ebay. Motorcraft plugs ebay or rockauto. FOLLOW THE TSB ON THE PLUG TORQUE SPECS
Changed the plugs already. Old ones were heavily eroded. Gas mileage is up with the new plugs but the misfire/stall issue still exists. Boots/springs all looked good visually.

The code scanner Steve suggested is on its way. Couldnt find it locally so I ordered it. Should be here this week.
 

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My vote is IAC due to your stalling issue, I've had the same problem with those engines in a Mustang.

Those 'mod' engines are pretty sensitive to misfires and will throw up a code pretty quick for failed coils. On my 5.4 F150 I could move a failed coil from one cylinder to another, clear codes, start it up and within a few minutes idling it would throw up a CEL for the cylinder where that bad coil was placed.
 

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Discussion Starter #15
Is there a cable from the pedal to the throttle, like the Bronco? Or is there a motor on the side of the throttle body?
Roger that. It is TBW. No motor. Cable from a bracket on the throttle body (I think) to the gas pedal.

Scanner should be delivered tomorrow... More info to come.
 

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Roller rockers are gay
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Much derp. So dense. Wow. :toothless
 

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On my 5.4 F150 I could move a failed coil from one cylinder to another, clear codes, start it up and within a few minutes idling it would throw up a CEL for the cylinder where that bad coil was placed.
That's standard diagnosis verification, because, when a misfire occurs, it can be the coil, plug, the injector or the cylinder itself, mechanically. I've used it on modular, Magnum and LS engines to narrow down the misfire cause.
 

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Discussion Starter #20
Okay - Here is what I have so far...

Codes Read - 0
Freeze Frame Data - 0

Live Data

First number represents Cold Idle in Park. Second number represents Warm Idle In Drive.

DTC_CNT = 0 / 0
FUELSYS1 =CL / CL
FULESYS2 = NA / NA
LOAD_PCT(%) = 27.5 / 27.8
ETC(F) = 106 / 194
SHRTF1(%) = 2.6 / -0.8
LONGFT1(%) = 0.8 / 0
SHRTFT2(%) = -1.6 / 0
LONGFT2(%) = 3.1 / -2.3
MAP(inHg) = 8.9 / 10.9
RPM(/min) = 1101 / 546
VSS(mph) = 0 / 0
SPARKADV(*) = 22 / 15
IAT(F) = 61 / 82
MAF (lb/min)= 1.164 / 0.520
TP(%) = 19.6 / 19.6
O2SLOC B1S12--B2S12-- / O2SLOC B1S12--B2S12--
O2B1S1 (V) = 0.725 / 0.100
SHRTFTB1S1(%) = 1.6 / 0.6
02B1S2(V) = 0.290 / 0.725
02B2S1(V) = 0.820 / 0.110
SHRTFTB2S1(%) = -4.7 / 0.0
02B2S2(V) = 0.1150 / 0.095
ODBSUP = OBDII / ODBSUP = OBDII
MIL_DIST (mile) = 0 / 0
FRP(PSI) = 39.9 / 39.8

Since DTCs Cleared

MIL Status = OFF
Misfire Monitor = OK
Fuel System Monitor = OK
Comp. Component = OK
Catalyst Mon = OK
Htd Catalyst = N/A
EVAP System Mon = INC
Sec Air System = N/A

Other symptoms noted when stopped, in drive, foot on brake:

Idle bounces between 520-580.
Car almost stalled but then surged up to 2200 rpm then back down to mid five hundreds. It had done that before, but I wasn't looking for it so I wasn't 100% sure I had felt what I thought I had felt. Now I know.

When at 35 mph, car RPM is around 1200. It is around this speed and an RPM between 1200 and 1500 that the shudder occurs.

I have not been able to do the TC test as Steve described yet. I will do that tomorrow when its not constant stop and go traffic and report back.

Thanks again for the help fellas...
 
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