Ok all;

Now that my previous problem is solved (thanks again), here is my next puzzler. A few months ago the "Service Engine Soon" light came on. Using RovacomLite I found the following fault codes:

THE MOTRONIC FAULT CODE MEMORY CONTAINS CODES FOR THE FOLLOWING CURRENT FAULTS -:

P0175 = MIXTURE ADAPTION FACTOR FRA BANK 2 DRIVE CYCLE C, WHICH HAS OCCURED 13 TIMES[/b]
(SIGNAL TOO HIGH, THE FAULT IS CURRENTLY PRESENT, THIS FAULT CAUSES MIL LAMP ACTIVATION, THE FAULT HAS BEEN DETERMINED AS INTERMITTENT).

P0172 = MIXTURE ADAPTION FACTOR FRA BANK 1 DRIVE CYCLE C, WHICH HAS OCCURED 17 TIMES[/b]
(SIGNAL TOO HIGH, THE FAULT IS CURRENTLY PRESENT, THIS FAULT CAUSES MIL LAMP ACTIVATION, THE FAULT HAS BEEN DETERMINED AS INTERMITTENT).



When I check these in the shop manual it seems that the fuelling is intermittently too rich causing the system to have to go full lean which causes the above errors.Being that there were no other faults such as oxygen sensors, etc, I tried to logically deduce what would cause the system to receive too much fuel and have tocompensate by going full lean and the only thing I could think ofwas that the purge valve on the EVAPS system was faulty and woulddump the fuelvapor load into the combustion system inappropriately. This is a 4.0 withthe Bosch systemand the advanced EVAPS.

BTW, I cleared the codes once, had the light come back on in a few days with the same errors, tried clearing a second time but the light wouldn't go off, and just now successfully cleared them again and the light is still off after a 15 minute drive.

Thanks;

Greg

 

Purge valve is a good place to start, also check your MAF #s. Although they usually fail lean (P0171, P0174) I have seen them fail rich. If your grams per second readings are over 6 at idle, I would replace MAF. Also check pressure regulator on fuel rail for leaking.

 

How many miles on your truck, have you replaced your 02's, wires and plugs?

 

Thanks to both dcox and Disco Mike. I'll try to look into both of those things tomorrow. BTW, it has 117K miles and it should have had plugs replaced at the 90K service but I'm not sure of the wires and I know the O2 sensors are original.

Greg