i have a 95 bronco with 5.8 engine that check engine light on codes are 12 and 26 any ideas what is going on truck idle rough and engine shuts down under hard acceleration but not die also tranny wont down shift.

any help would be greatfull

 

What have you checked so far? Check Ford fuel injection .com for codes.

 

26 points to the MAF

12 is a engine control issue about high rpms.

 

checked iac volts good and ohms good also pulled and cleaned iac and intake no help still acting up looks like iac not seating and moves easy have read that 26 was tranny code and if a oil and filter change would help

 

Did you change to a K&N air filter?

 

Code 12 is indicative of a coked (not choked) throttle body. Inspect and clean especially behind the throttle plates. The problem caused by this is that the computer is unable to push the engine idle to its upper idle limits if the throttle body becomes too badly clogged (coked). This Code ONLY presents itself during the KOER test.

With this code there is a very remote possibility of a mis-adjusted throttle plate stop screw. However, unless someone adjusted the stop screw, the likelihood of it moving on its own is virtually impossible.

Code 26 (Specific to the 5.0 and 5.8L when dealing with the Bronco but with totally different meanings for each engine!) For the 5.8 Code 26 indicates an over-temperature reading from the transmission oil temperature sensor. IT HAS NOTHING TO DO WITH THE MAF. Once again... incomplete information that would have caused greater harm than good and caused greater expense and work than was ever needed!

 

got codes with koeo test i opened the plates and sprayed a can of b12 in there is there any something else i need to do to get rid of code 12 and is there any thing i can do to get rid of code 26 checked trans fluid it looked high and thin didnot smell burnt will a fluid change help will try that this weekend or do i need a rebuild trany still pulls strong when it runs right

 

A good cleaning of the throttle body should clear up Code 12. If you haven't cleaned the IAC valve body, you might do that as well. It controls the air flow through the throttle body at idle.

Code 26 may be left in the memory from a past issue.

I would suggest completing the cleaning and clearing the memory/codes, driving the truck for about 30 minutes and re-testing. If any codes come up again, then you may need to delve further into the issue.

 

erased codes after the cleaning and codes came back

 

Try cleaning it again, take it off and really clean it good

 

So BOTH codes are there? As g-k50 said, cleaning should probably include removing the TB and separating the IAC valve body from the throttle body. Code 12 is dependent on the computer's ability to control idle rpms. The IAC valve is one of the direct links to that control. If it is clogged the full amount of air that is supposed to flow through the valve isn't getting down the intake and that will keep the rpms down.

The return of Code 26 leads me to believe there may be something wrong with the sensor itself unless the transmission runs too hot all the time.

To be absolutely certain that the codes are cleared disconnecting the battery for about ten minutes will remove even stored memory codes.

 

 

Cool, glad it worked out.

 

been running it for 2 days now and everything is fine no more check engine light and runs smooth

thanks to all for the help