Engine intermittently runs rough, then smokes

PATMAN242

MEMBER
1994 FORD ESCORT

Hi-

I have a '94 Ford Escort. When driving down the freeway, all of a sudden the engine will start to sputter, with significant loss of power. After (usually) 10-20 seconds, it will recover, and run smoothly. It does this every 3 minutes or so; a load (such as a hill) tends to bring it on. There is no "check engine" light, or any other indication. Temps are fine.

I have replaced the plugs (correctly gapped), plug wires (replaced in brackets to keep separated), and air filter. I also inspected the MAF sensor when I had the air filter off; it looked perfectly clean. I cleaned the battery terminals. I'm down to the fuel filter, I think.

Chilton's says I must remove the rear seat in order to de-pressurize the fuel system before fuel filter removal. I'ver tried to remove the clips holding the seat cushion down, with no luck There is obviously a trick to it I don't know.

My questions are:

Is the fuel filter the likely problem? (I have never replaced it, owned the car about 6 years now) If so, how the devil do you get the rear seat cushion out? If not, what is the likely cause? O2 sensor?

Any help would be appreciated.

5 Replies

RACEFAN966

MECHANIC
5,029 POSTS

Ok I would replace the fuel filter first no questions asked. It should be replaced every couple of year anyhow. If you change it after it sat overnight then the line pressure will not be there. You will loose a little fuel but not alot.

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Wednesday, June 24th, 2009 AT 9:57 AM

PATMAN242

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3 POSTS

Replaced the fuel filter; no change. I did an hour test drive, and noted the following:

1) It SEEMS to be only a narrow range of RPM where this happens- usually between 2000 and 2250, regardless of gear. Of course, the effect is exaggerated when in 5th gear, because it makes a bigger difference in speed. It's harder to tell when it's happening in lower gears.

2) Loading the car seems to bring it on also. For instance, a standing start from an uphill freeway on ramp made it happen almost immediately.

3) The work I've done over the last 2 days (plugs, wires, air/fuel filters) has made a noticeable difference. It doesn't run rough as often, or as badly. It's still happening in the same manner though.

I'm afraid I've hit the limit of my automobile knowledge, so any ideas would be welcome.

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Wednesday, June 24th, 2009 AT 2:21 PM

RACEFAN966

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OK do you have a digital multi meter? If so I would like to walk you through a test to test the Throttle possition sensor. Let me know what you would like to do. THanks.

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Thursday, June 25th, 2009 AT 9:07 AM

PATMAN242

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3 POSTS

Yes, I do have a digital multimeter.

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Thursday, June 25th, 2009 AT 12:06 PM

RACEFAN966

MECHANIC
5,029 POSTS

Ok I need you to take a paper clip and back probe the grey wire with the red stripe. Now hook up you multi meter and set it on the 20 volt scale and turn the key on engine off and record the voltage. Now slowly lift the throttle (key on engine off) and watch the voltage it should steadly increase with no drops or glitches go to full open throttle and record the voltage. It should read with throttle closed.8 to 1 volt and with throtlle wide open should read 4.5 to 5 volts. It should steadily increase with no drops or glitches in voltage as you open and close the throttle. Get back to me with what you find and we will go from there. Thanks.