What would cause an intermittent lean condition?

[BigHairyMonkey]

Usually the car would only do this when it was cold, but lately it has started to pick up in frequency. My car is really moody part throttle... sometimes it runs great and has amazing throttle response, but sometimes as im driving ill start feeding it gas and itll start bogging down; as if its not getting a reading from my right foot. Today it happened REALLY bad, usually it happens for a sec or two and clears up but today as i was driving i shifted into 3rd and got into it about 20% it started bogging... i gave it 30%.. no differene i shoved my foot into it about 60% ( i get some pops outa the intake manifold as i guess its running lean)..nothing then all the sudden like a light switch, BAM shoved in my seat and the car takes off like normal??! The car runs like a raped ape at WOT but at part throttle it seems like the power/throttle response comes and goes. What could be the culprit?

-02 sensors have less than 4 months on them
-IAT less than 2 months
-IAC less than a month
-ECT less than 2 months
-Only old sensor on the car is the TPS. (but it is set @ .99 at idle)

 

[BigHairyMonkey]

also my idle surges from 900-1100 randomly at stop lights and some times gets hung up at like 1000... leading me to believe it may be a bad TPS. oh and yes ive read jrichs checklist but this is more than an idle issue to me.

 

[ttop88]

Sounds like a slow reacting O2 sensor. You can check the tps with a dig. multi meter.

 

[PUNISHER RACING]

+2 on the whole o2 sensor reading thing, I am not sure if the Ford's are heated or not. Its fine after the car has run a while?

 

[jrichker]

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

See http://www.troublecodes.net/Ford/

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.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

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 $30.

See the "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.