Here is my dilemma (all specs are in my sig)

I have been working on a problem for about a year now that is bugging me. About 150 to 200 miles after resetting the PCM my truck will not idle/die if I am at a slow speed, like in a parking lot, and let off the gas. Sometimes it will almost die and then go back up to normal idle and sometimes it will just die. If I reset the PCM it works perfect for another 150 to 200 miles and then the problem starts all over again.

Trying to fix this problem, I have[*]replaced Plenum gasket[*]replaced IAC[*]replaced header gasket (incase I was sucking air)[*]I cleaned O2 sensors[*]I cleaned all the TB[*]I checked the TPS for .7v and cleaned it[*]put fuel injector cleaner in it (sea foam, techron, and lucas oils)[*]replaced the plugs with autolite 3923's
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The truck runs perfect even when this problem is going on except for the scenario I stated above. I don't think I am running rich because I get 16 MPG in town and 19 MPG on the highway and I have pulled the spark plugs and the look good.

ANY IDEAS OR HELP is appreciated.

Brad[/align]

 

My wifes blazer did the same thing but was throwing a code. Check the evap purge canister and all the lines for leaks. Also check evap purge solenoid. Just a guess.

 

Could be themap sensor. See if you can get your hands on a scanner and look at you map reading vs. manifold vacuum, and look at your fuel trims. On the map sensor reading: map should start out (key on-motor off) at what ever the atmospheric pressure is that day. When you start the motor the reading should be the starting reading minus manifold vacuum. May also be that the upstream 02 sensor needs more than cleaning.

 

mine did the same thing after I reset the PCM, turns out the battery leads weren't connected tight enough and the truck would start up real week and then die at low RPMS.
Replaced the terminals $4, and it hasn't done it since.

 

I would replace the pre cat O2 and then see what happens.

 

Ganderguy was correct it was my battery connections...All of this guessing and it was something simple and cheap....thank to all for the ideas.

Brad

 

That's cool you posted back. More people should do this so that, when someone has a problem, they can come here and use the search function to find solutions.

 

Just curious about one thing. How did you clean your O2 sensor and what did you use? I was under the impression that these things were NOT to be cleaned with anything. Only replaced.

 

I used TB cleaner....all i did was take out the O2 and used an old tooth brush to lightly scrub it....but it did not look bad and really looked no different when I was done...so I am not sure if that worked or not. Here is a link that I followed instructions from

http://www.gnttype.org/techarea/ecms...O2sensors.html

Brad

 

Brad, good link.
My understanding is that a constantly varying O2 sensor voltage indicates proper operation. This has also been my experience monitoringa sensor while driving several different vehicles.

[sm=smiley25.gif]Question: If an O2 sensor has say 100,000 miles on it and the voltage varies indicating it is working could it still need to be replaced becauseit developed an offset?