1991 Ford Escort Engine running rough at idle and steady

Tiny
BHANS
  • MEMBER
  • 1991 FORD ESCORT
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 214,565 MILES
The engine idles rough, but will run fine while driving. At times the cat will want to stall at stop lights. Also, when driving at a steady highway speed ogff around 60mph the engine will start chugging and act like it is going to stall. It has never stalled, but I have to either let off the gas or give it gas to get it running smoothly again. I have recently changed the plugs, wires and the fuel filter.
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Saturday, June 6th, 2009 AT 6:54 PM

5 Replies

Tiny
RASMATAZ
  • MEMBER
A large vacuum leak can lean the air/fuel mixture out to such an extent that an engine will not idle at all. An EGR valve that is stuck open at idle can have the same effect as a vacuum leak. So too can a loose positive crankcase ventilation (PCV) hose, a leaky PCV valve or the wrong PCV valve (one that flows too much air for the application). If somebody replaced the PCV valve recently, they may have installed the wrong PCV valve. The rough idle in all of these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all. Lean misfire will show up as elevated hydrocarbon (HC) readings in the exhaust, which may be enough to cause a vehicle to fail an emissions test.

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
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Monday, June 8th, 2009 AT 4:07 PM
Tiny
BHANS
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Thanks for the info,

Could one of these issues also be causing the chugging I am getting when the car is warm and at a steady 60 mph?
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Tuesday, June 9th, 2009 AT 9:42 PM
Tiny
RASMATAZ
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All of them what have you checked so far?
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Wednesday, June 10th, 2009 AT 1:50 AM
Tiny
BHANS
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To this point all I have done is replace the plugs and wires, and changed the fuel filter. I use a fuel treatment/injector cleaner every oil change, so I would like to think it is not the fule injectors. My mechanical skills area somewhat limited, and am looking for a good place to start. I would think I would be capable of changing many of the sensors/ valves you have mentioned. Where should I start?
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Wednesday, June 10th, 2009 AT 8:51 AM
Tiny
RASMATAZ
  • MEMBER
Start by checking the fuel pressure making sure its within specs, mass airflow sensor and idle speed control and EGR valve
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Wednesday, June 10th, 2009 AT 8:59 AM

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