For the past few years I was convinced the stumbling hesitation at times was due to ethanol fuel. Truck could sit a few days up to a week and a half and run terrible. ( humidity is bad here) Winter I never had problems always ran like a champ . When running bad ,the humidity was terrible and after running it a while it seems to do great. Each day I ran it consecutvely it would do good no matter the humidity .When the hesitation started it sat and would feel stumbling hesitation and backfiring . Odd I know but today , as the humidity is bad I was cleaning the truck engine of grease +grime and it magnified the problems described as if sat for weeks . Yes water found it way in somewhere and it bucked kicked and would hardly start once started and it dried( ran it a while) seems it runs good all the bad symptoms went away. Pulled codes koer = 412 311 538 , koeo all ok 111 . Now I am thinking the humidity is causing problems and running the truck after sitting ( getting it warm , hot, it does better . The fuel is not my problem, any suggestions thanks TR

 

fyi after clearing codes I get the code 311 538 om koer koeo 11 thanks TR

 

Don't worry about Code 538. It just means you didn't perform the "goose" test during the KOER.

Code 311 indicates that the Thermactor system was inoperative during the test. The Thermactor System consists of the air injection (smog) pump, the associated plumbing, and the diverter valve (behind the passenger side cylinder head on the V8's). This typically means that the system could not achieve the correct EGO (Exhaust Gas Oxygen) levels during the test. Now, if the engine was not warm enough to have dropped into closed loop operation, this Code will ALWAYS rear its ugly head. Otherwise, if the engine was at normal op. temp. then check the vacuum lines running to the diverter valve and at the TAB (Thermactor Air Bypass) and TAD (Thermactor Air Diverter) solenoids (mounted behind the ignition coil). While you are at it check the wiring to these two solenoids as well for corrosion, loose connections, etc. In the event there are no issues with broken or disconnected vacuum or electrical lines, you will need to engage in the far more tedious procedure of troubleshooting the TAB and TAD solenoids. Let me know if this becomes the case and I can give you the details for testing them.

As for the humidity issues, make certain your distributor cap and rotor have good clean contacts. Corrosion and soot on the rotor or the electrical contacts in the cap will cause terrible performance issues. Make sure the cap isn't cracked either as this will allow moisture to condense inside the cap in humid conditions. This leads to corrosion of the contacts on the cap and on the rotor causing the condition already described.

 

Thanks Grey, seems this truck has been doing this for a while, like mentioned earlier, winter ,I do not have a stumbling problem , truck can sit a few weeks .One thing I didn't do winter is check codes .when responding to the bucking stumbling I removed cap and found soot on the rotor button, it was lighting- thundering, so ill inspect it better .. Also checking the vacuum lines carefully along with the tab and tad solenoid. I know first hand how much of a pita electrical connections can be . Honestly the symptoms are it runs bad in humid weather after sitting a while ,fall spring winter are ok . I am also wondering since the truck engine heats up what else can be making these symptoms occur. I can rule out plugs and wires. as all were changed under these same problems a while back with the same results. As a stab in the dark, any other engine(motor) gasket, component gasket ,intake exhaust gasket that anyone could think of which causes the same issues ,help appreciated and as for coming weekend, I will check all mentioned. Thanks TR

 

I am wondering if you might have an ACT sensor that is going south on you. Both the ACT (Air Charge Temperature) and the ECT (Engine Coolant Temperature) sensors can cause performance issues if they "stick" at a given resistance value since they should change resistance as they warm up. The primary problem with troubleshooting these issues is that if one of em "sticks" at a resistance value that is WITHIN the range that the computer "expects" to find, no fault Codes will be thrown. Problem being that if that resistance value is telling the computer that the engine is warmer or cooler than it really is, then performance suffers..

I have posted the chart that indicates what the resistance value for these two sensors SHOULD be at certain temperatures before. The problem is that you can't really test them on the truck since the system will get really screwy if you completely disconnect them. I know several folks who have just opted to replace them but why throw money at it if it doesn't fix the problem. You can, however, remove them and use the oven to heat them up and check resistance values. (NOT THE MICROWAVE)!

 

In other words: bake them! .

 

Bingo! And if you have an oven thermometer, you can take them out and check them at a few different temps... Just like you would with cupcakes, albeit cupcakes taste better.

 

I won't even ask...

 

Lol , something else to check , this has been going on for a while and I will check each item posted and more , I can use a torch indirectly for the cololant and act sensors, along with a pipe thermometer and a fluke .

 

That will work. Just be careful not to melt the electrical connectors. Take the reading with the sensors disconnected from the wiring harness to ensure you aren't getting a false reading because of resistance in the harness.

 

Thanks will do , seems my weekend is planned ,TR

 

FYI , update I checked all vacuum hoses, no problems took the act sensor out ,it was sooty, carbon mess so I replaced it. I have let it sit for a four days and it seems to be ok, hadn't read codes ,but will soon . Still need to clean distributor(underneath) cap and test or replace ect sensor . Thanks TR

 

Ok , seems I have read codes after a couple of weeks after my initial problem of hesitation(after sitting awhile), all ok, checked vacuum lines, tested coolant sensor, replaced act sensor.it was sooty /carbon looking. Now it seems the act sensor was my problem ,I can quit degrading ethanol fuel.( lol)This problem has occurred for the last 5-8 yrs .It had the symptoms of spark plug misfiring at low and high speeds and after it was run a while it would go away , thanks Grey, TR