CEL Help needed

[markfagus]

Ok guys, here is the scoop.
88 3.0 auto fresh TPS and HG a few months ago. Also replace all tranny solenoids and replaced a malfunctioning ECU.

Over the last few months the Check engine light periodically came on but when I shut truck off and restarted light would stay off sometimes for a few miles, sometimes for a day, sometimes 3-4 days. I finally pulled the codes and got a 22- Coolant temp sensor. I replaced that Saturday. Then Monday CEL light comes back on, I pull the code and it is 21-oxygen sensor. So I replace that last nite.
Today I drive about 20 miles and the truck seemed to be running smoother, then the damn Check light came on again!

So I pull the codes and I am getting 3 different codes:

25 - Air–Fuel Ratio Lean Malfunction
26 - Air–Fuel Ratio Rich Malfunction
51 - Switch Condition Signal

Is it logical to get a 25 and 26 at the same time? Seems odd to me.

Most importantly, what can I do next to fix this once and for all?

thanks

Mark

 

[AddictedOffroad]

Are you running an open air cleaner? Could also be a slight vacuum leak or exhaust manifold leak.

51 code is a TPS code. Usually means its out of adjustment.

 

[markfagus]

I am running a stock air box with a K&N filter. I did not have time to replace the TPS as I was traveling for work a lot so I had a friend who owns his own auto repair shop install it for me. A little bit of additional info; when I first started it up after replacing the O2 sensor it seemed to idle very smooth. Now the truck seems to have a slight miss or stumble at idle (especially when cold) but as soon as i start driving it smooths out, I dont notice any hesitation and my gas mileage has not suffered. I am consistently getting 18.5-19 MPG. Also, when the CEL lite came on tonite it was under hard acceleration going up a hill traveling at 45 MPH and the tranny had just downshifted.