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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23001
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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2003 Ford Focuse. 2.0 dohc. The rpms go up and down at an

Customer Question

2003 Ford Focuse. 2.0 dohc. The rpms go up and down at an idle. When I step on the gas. It stalls and loses power. Have to gradually go up to speed.
Submitted: 8 months ago.
Category: Ford
Expert:  roy replied 8 months ago.

good afternoon my name is ***** ***** I will assist

is the check engine light on??

2 common issues.

mass air flow sensor, connector or the hose going from it to the throttle body

vacuum leak on the pcv hose from the top or valve cover to the throttle body

Roy

Customer: replied 8 months ago.
No check lights.
Expert:  roy replied 8 months ago.

ok, I would start by checking the connector on the mass air flow sensor. then check the line for the pcv from the throttle body to the valve. it is common for the 90 elbow to rot out and leak vacuum giving you these symptoms

Roy

Customer: replied 8 months ago.
I've checked the mass air flow sensor. Cleaned with MAFS cleaner. And cleaned plug with electrical connection cleaner.
Expert:  roy replied 8 months ago.

you cannot clean the sensor. there is no cleaner that can get the burned carbon off the hot wire. it will remove loose dirt but not the burned on carbon.

what else have you done??

did you check the pcv line??

Customer: replied 8 months ago.
I only see one line off the valve cover and it Gos in to the bottom of the filter housing. I've done alot. I've gotten to the point of replacing all the parts and returning them when it dosnt do anything. But I'd like to go through the steps you think will help.
Expert:  roy replied 8 months ago.

do you have a scan tool??

Customer: replied 8 months ago.
I looked at the 90° line from the throttle body to the egr valve. I see know rips in the o rings or cracks in the plastic lines
Expert:  roy replied 8 months ago.

ok, I attached a picture for you to be sure we are talking about the same thing. look for the hose being collapsed or squishy.

Roy

Customer: replied 8 months ago.
That's not the correct one for this car
Expert:  roy replied 8 months ago.

there are 2 different 2.0 dohc. I checked both and they are the same. I believe you because sometimes these manuals are not accurate

did you check the elbow to be sure it was not collapsed??

dod you have a scan tool??

Customer: replied 8 months ago.
it have a scan tool.
Customer: replied 8 months ago.
I apologize it's a 2002
Expert:  roy replied 8 months ago.

ok, thanks

while I am looking for the new info, get the long term trims for me from the data screen

Roy

Customer: replied 8 months ago.
I see 4 lines directly under the TB
Expert:  roy replied 8 months ago.

yep, check them all as well as the other ends. especially at the valve cover. very common failure

Roy

Customer: replied 8 months ago.
Lt ftrm1 25.0 staying steady. Do you want ST as well. No other LT readings.
Customer: replied 8 months ago.
All the rubber and springs look good. There is no line from the VC to intake.
Expert:  roy replied 8 months ago.

no, shorts mean nothing at this point it would be from the valve cover to the throttle body in the back

possible failures for the long term up like that are

pcv valve itself failing

mass air flow sensor or hose

vacuum leaks

low fuel pressure. you can have fuel pressure but not enough. the pcm will keep calling for more fuel but cannot get it due to low pressure.

Customer: replied 8 months ago.
What should fuel pressure be at. I've replaced on 1/2 line at the bottom of the intake to a hard pipe that gos uner the exoust manafold. I can do a vacuum test if you know what the readings should be.
Customer: replied 8 months ago.
Ive replaced the MASF with a known good one. No change. Put the old one back on when it did not help.
Expert:  roy replied 8 months ago.

what vacuum test???

the only test I would do for that is use a smoke machine to inspect for leaks.

ok, I never use used parts. does the voltage change on the mass air flow when revving the engine up and down??

the fuel pressure is more important

Customer: replied 8 months ago.
If I put a vacuum Gage on the vacuum one vacuum lines it should be in-between a psi while running. If it's not there's a leak. I'll check the links
Customer: replied 8 months ago.
It was a new mafs
Expert:  roy replied 8 months ago.

thats engine vacuum, not external leaking. that is done with a smoke machine. you pressurize the lines and look for leaks

Roy

Customer: replied 8 months ago.
Fuel at 40 psi with Gage.
Expert:  roy replied 8 months ago.

ok, thats good.

take some carb cleaner and spray around the intake manifold and see if the long term trims change. that is also a common area for a vacuum leak

Roy