Ford '98 Exped, 87k mi, have all the lean mix codes: 136, 156, 171, 174,
1131, 1151. Replaced O2 sensors 3 k mi ago, there was no change before or after. The matter gets worse: started about 9 months ago with engine light and heretic idle (500 rpm to 1200 rpm), now it gets at the level that it stalls at idle. The sensors read the temperatures right (bought the OBD II to pc interface), for some reason acceleration reeds at 19%, and you can here at times some clicks followed by rpm jumping high... Really ruff idle right now, and as you step on the gas, it takes for a while before it takes off. Any thoughts?
The problem was the broken elbow underneath the Idle Air Control valve (the elbow was part of the vacuum circuit bringing fumes from the PCV on the passenger side of the engine)at the very rear of the engine. It couldn't be in a more weird location and difficult to replace... I found out the leak late in the day, did not have time to purchase a new one; however I did cap it with a plastic cap, and the engine works like a champ now: all loops closed, and it runs very smooth at 685 rpm.
On a personal note: I am not a cheap skate and I believe everybody should make a buck, including the dealer. However, this matter changed my view of a manufacturer's dealership: I took the car to the Ford San Bruno dealership and they suggested replacing all the O2 sensors AND the DPFE sensor ($850 total quote)) and it was obvious not even close -- charged me though the $150 for "diagnostics" I couldn't take it back to them... All error messages were suggesting a lean mixture, and the fuel pressure was just right, and while stepping on the gas it ran very nice -- what the dealer was saying did not make sense, hence my post.
Your suggestion re-enforced and cleared for me the direction for troubleshooting, and trust me, I needed it since that was the most hidden vacuum connection to the manifold... Back to my San Bruno CA Ford dealer -- either the most unprofessional there ever is, either crooks -- the choice is theirs; oh there is another option, and that is incompetence.
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