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AMEDEE
AMEDEE, FORD TECHNICIAN
Category: Ford
Satisfied Customers: 26055
Experience:  ASE CERTIFIED TECHNICIAN ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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I have A 2006 FORD Freestar with the 3.9 engine. It surges

Customer Question

I have A 2006 FORD Freestar with the 3.9 engine. It surges at 3000 rpms and will not go above 3000 rpms with no load in nutral.
JA: How many miles are on the car? Is it an automatic or a manual transmission?
Customer: automatic and a little over 200000 miles
JA: What is the make/model of your car?
Customer: Ford Freestar with the 3.9
JA: What year is your '06 Freestar?
Customer: yes
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: New crank sensor only code is p0420
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 8 months ago.
Category: Ford
Expert:  AMEDEE replied 8 months ago.

Hello and welcome!

My name isCustomerand I can assist you with your question.

Expert:  AMEDEE replied 8 months ago.

How long has the check engine light been on?

Customer: replied 8 months ago.
about a year
Expert:  AMEDEE replied 8 months ago.

Do you know what the engine vacuum is at?

Customer: replied 8 months ago.
not at the moment, but I can check
Expert:  AMEDEE replied 8 months ago.

Can you check it tonight?

Customer: replied 8 months ago.
I can, I checked the injectors with a noid light and they do not fire when it goes into the surge and do when it comes out of it.
Expert:  AMEDEE replied 8 months ago.

Do you know why?

Customer: replied 8 months ago.
no that is why I changed the crank sensor thinking maybe that is the problem
Expert:  AMEDEE replied 8 months ago.

I suspect your exhaust is plugged.

Customer: replied 8 months ago.
ok that sounds logical
Customer: replied 8 months ago.
would that cause the injectors to stop firing?
Expert:  AMEDEE replied 8 months ago.

Not only you have the converter code.. which I suspect your convrerter is plugged, but it also this will prevent air flow through the engine and cause this condition your experiencing.

YES, this will affect fuel delivery.. because it is reading engine vacuum.. which is low or being affected due to plugged exhaust.

Customer: replied 8 months ago.
Ok I will check the vacuum
Expert:  AMEDEE replied 8 months ago.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

Please let me know if you have any further questions.

Customer: replied 8 months ago.
Ok I will
Expert:  AMEDEE replied 8 months ago.

Sounds good thank you very much!!

Customer: replied 8 months ago.
Ok still haven't found the problem. The vacuum drops to from 20 to 5, the more I slowly open the throttle the more it drops. I took the first oxygen sensor out before both catalytic converters and no change still surges at 3000 rpm's also disconnected the muffler. Could the ECM be messing with the timing bad, Cam sensor?
Expert:  AMEDEE replied 8 months ago.

Hello!

What is the exhaust back pressure at?

Customer: replied 8 months ago.
The most I can get is 1.5 P.S.I. at 3000 where it starts to surge.
Expert:  AMEDEE replied 8 months ago.

Hello and sorry for the delay!

If the exhaust checks out good, based on my experience this is a severe lean condition due to low fuel pressure or a bad mass air flow sensor.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

Please let me know if you have any further questions.

Expert:  AMEDEE replied 8 months ago.

Hello! It'sCustomerfrom just answer.

I am just checking in to see if you need any further assistance?

Let me know!

Customer: replied 8 months ago.
Fuel pressure is 54 psi and the Freestar runs the same with the MAF unplugged
Expert:  AMEDEE replied 8 months ago.

What is the oxygen sensor readings at under a load when this problem occurs?

Customer: replied 8 months ago.
I will have to get back to you on that in the morning. My scan tool has been acting up so I moved onto other things till the weekend.
Expert:  AMEDEE replied 8 months ago.

OK

Customer: replied 8 months ago.
Average voltage under load for Bank 1 sensor 1 = 0.4, Bank 1 sensor 2 = 0.4
Average voltage under load for Bank 2 sensor 1 = 0.4, Bank 2 sensor 2 = 0.6Short term fuel trim Bank 1 sensor 1 = 0.7, Bank 1 sensor 2 = -1
Short term fuel trim Bank 2 sensor 1 = 0.9, Bank 2 sensor 2 = -1
Expert:  AMEDEE replied 8 months ago.

Here is a good test that will help pinpoint the root cause.

Under safe road conditions, a wide open throttle acceleration is performed. Try to maintain WOT for at least 5 seconds. 10 to 20 seconds would be better. (this of course is when the problem occurs)

What will the pre cat oxygen sensors do?

Will indicate rich

Should the barometric pid change?

Should remain stable! Very important!

What will air flow do?

Max out. Volumetric efficiency. Engine load 100%
(Engine load Parameter on scan tool should go close to 100%)

Results

Poor acceleration, rich exhaust, and good Barometric pressure = restricted exhaust or late ignition timing.

Poor acceleration, rich exhaust, low or decreasing Barometric pressure = intake path restricted

Poor acceleration lean exhaust and good barometric pressure = fuel delivery concern.

Poor acceleration, lean exhaust and low barometric pressure = air flow measurement error. (Ford has this problem with Mass air flow sensors)

Note: Some vehicles Barometric pressure is not updated until Wide open throttle.

Customer: replied 8 months ago.
Ok Oxygen sensors go low all the way to 0.0 on both banks
Barometric pressure is constant 14.94
Mass Air Flow is 16.2
Calculated load is 99%The all injectors are not pulsing (no electrical current) it seems like for 6 revolutions then they pulse for maybe 12 revolutions. This is just what it sounds like. I have observed the no electrical current with a noid light in the injector circuit. I think this is getting out of my league and I will take it to a ford garage for diagnostic unless you have more information.
Expert:  AMEDEE replied 8 months ago.

If the oxygen sensor readings are extremely lean under a load, this is the problem. The engine is STARVING for fuel. Fuel pressure needs to be checked and verified, the mass air flow sensor signal needs to be checked and verified and the air intake snorkle from the mass air flow sensor to the throttle body needs to be checked and verified free of cracks and or rips.

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