misfire problem


New Member
Apr 13, 2003
ive been having a wierd problem lately with my car that i cant figure out. its a 1991 gt motor is all stock. the problem is kind of like a misfire/bucking/hesitation mostly at idle and low rpm. just recently did cap/rotor/plugs/wires/pcv and new coil and the problem is still there. the thing that gets me though is that sometimes it will be running perfectly and then all of a sudden the idle will change and it will start to buck at low rpms. pulled codes and got none. any ideas guys?thanks
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Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.


See http://www.troublecodes.net/Ford/
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.
Don't forget to clean the IAC and check the TPS voltage.... key on engine off voltage should be about .995
You can slot the bolt holes in the TPS to make it adjustable.