Hi, i started the car and the engine clunked and started running rough. i had a friend check the engine with a computer and the #1 cylinder was missing. i replaced the coilpack and now the spark plug for the #1 cylinder. the car is still running very rough like it is missing. is there a chance all the plugs fouled out?

SOURCE: Service Engine soon light, codes P0301 and P0171, replace plugs

Hi,, Well the service engine light comes on when your car needs to be tuned up, this happens when the timing belt needs changing or nearing its life span. Basically it involves changing the belt (optionally >) engine oil, transmission fluid, radiator coolant, fuel injection and throttle body servicing, changing gas filter, air filter etc. Its to prevent damages to your car. After its serviced the mechanic will need to clear all error codes and reset the cars computer. Clearing the error codes is done with a diagnostic tool, to reset the cars computer , remove the negative battery pole and press the brak as far as it will go, wait 60 second release and reconnect the battery pole. Some vehicles may need to be caliberated if it has an electronic throttle body system

SOURCE: misfire in cylinder 1 2001 mercury sable

Next change swap the injector with another and see of the problem moves.  If it does it's a bad injector.  

SOURCE: running rough, spark plugs, distributor cap, rotor

First thing you need to know is which cylinders are missing. Then, don't forget there is an engine beneath the electronics. Do a quick test with a vacuum gauge and do a compression test. Check the distributor shaft for side play. If everything checks out good, then do electronic component testing. have a code check run (many parts stores do this free) and get a chiltons or haynes manual and follow test procedures in there.
I refrain from giving repair suggestions with problems like yours because people keep changing instead of testing parts. When I work on my vehicles or other peoples cars, I do testing to avoid buying expensive parts that most times won't correct the problem. At this point the most I'd suggest is to clean the mass air flow sensor wires with a Q-tip and carb cleaner...that often helps and is free. If you run into a problem with whatever you find, ask and I'll try to help.
good luck

Testimonial: "I followed suggestions, it did helped some what."

Vincent G

• 2363 Answers
• Posted on Dec 19, 2009

SOURCE: MIL indicates cylinder misfire on 1, 3, and 5

Check for

vacuum leaks on intake manifold,

the air tube between the air filter.

intake manifold vacuum hose.

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clean throttle plate with Berryman carburator cleaner

SEE sample picture HERE
===

Also remove carbon built up behind the EGR valve and the EGR passage tube.

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Vacuum leak WILL offset the intended 14.7 to 1 air fuel ratio.

More un-metered air (leaks) will lean out the fuel mixture.

Use small amount of Berryman carb clearer at potential air leak area will help you identify trouble spot.

At idle,just spray and listen for the RPM surge.

The in-rush of carb clearer will increase the RPM on the motor.

Record the problem spot(s) and address it later.

===

EGR carbon built up require 2+ hours to clean from start to finish.

You will need a new EGR base gasket before your start.

Locate and remove the EGR valve after the vehicle is cool down.

Carefully record the connector and vacuum line (for older vehicle) location by drawing an easily to follow diagram.

Remove the EGR valve.

Inspect the location of the carbon built-up inside the valve and the EGR passage tube.

SOAK these areas with WD-40 spary.

You will need a small screwdriver,cloth hanger and lot of newspaper and time to get this cleaning done right.

RE-SOAK the carbon and let it sit for over-night will also help.

One the last round,pass a shop vacuum of the EGR valve and the passage pipe.

Install the new EGR gasket and connectors.

Allow the vehicle to warm up outdoor to burn up any remaining WD-40.


Take it for a test drive.


Please rate my answer if it's useful to you.


Cheers,

Mustgo

SOURCE: engine light on, idles rough. had engine light diagnosis.replaced

See if you can get the codes. If it is still number 4 only (probably a P0304) it could be the fuel flow through injector 4. Try some Techron cleaner and make sure number 4 plug isn't fouled. Also get the compression checked on number 4.

If not, it could be the ignition control module assuming all other changes have been made. If you get a code it will help. A P0300 would point toward the ICM. If it is number 4 only it could still be the ICM. Expect around $150 for the module if you do it yourself. The ICM may be under the coil pack. If you are getting a P1361 and/or P1362 it could be the Cam position sensor. They are around $40 and are usually near the number one cylinder. Mine is hiding under the water pump pulley. It is a Buick with the 3.8 engine but the principal is the same.