Too Lean??
 

86 GT w/HO 5.0, 5spd.

What would cause this car to run lean only when the engine is warmed up. When the engine is cold, it has excellent throttle response, after it warms up, the throttle response is still good, but has a bit of a lag to it. Also, when the engine is revved when it's warm, the pipes have an odd cackle when the engine decellerates. Only in nuetral does the cackle occur, not while driving and gearing down.

What mods does your car have?

Stock.....

I ran a bottle of fuel injector cleaner through it recently, that helped with the surging idle. The other symtoms are minor, but they still bother me....any ideas.

Thanks

Jeremiah

try checking your fuel filters... they could be clogged and need replacing... but what makes you think its running lean??? just curious??? but it could also be your injectors... try that for a start see what the results are and we can go from there...

steve

That doesn't sound like a fuel filter or injectors to me. It only does it when the car warms up so if it were either of those it should do it all the time. Have you tried pulling codes yet?

Popping in the exhaust when free revving the engine is a symptom of a lean mixture. Only being a problem when the engine is warmed up means it's not injector or filter related, as mentioned. When cold, it's in open loop, and rich. That's normal. I am suspicious of the O2 sensors, but you really should run a KOEO and KOER self test and see what codes come up.

Take care,
-Chris

Could you tell me more about these self tests......Thanks.

I am new to EFI, Sorry for all the questions.

Thanks for the help.

Jeremiah

My guess would be the O2 sensors. The surging idle, and unusual air to fuel ratios are common indicators.

O2's would be my guess too, but I'd try to get some codes first. There are a few ways to pull codes. A code scanner which you can buy from Auto Zone (get one), or using a jumper wire/ohm meter/engine light. Here's some more info for you:
http://ratnin.home.mindspring.com/eec_test.htm