Engine Performance problem
2004 Kia Optima 4 cyl Front Wheel Drive Automatic 140000 miles
was getting p0131, p0134 and p0171 codes. I changed the #1 o2 sensor on bank 1 and the 131 and 134 went away. The 171 remains. Have detected what seems to be a vacuum leak around the throttle body. Sprayed arisol, tried propane, unable to find leak. No vacuum to egr valve (replaced it anyway). Followed line to egr solenoid valve and to throttle body. There are three vacuum lines on top of throttle body, one has vacuum (its marked P), the other 2 have no vacuum. Are they supposed to (I think so)? If so, are they gummed up and plugged? It seems weird for the one to have vacuum and not the other two. If the two with no vacuum are gummed up, why didn't the other one gum up too? I opened the throttle and felt the inside top, I could feel the hole of the one with vacuum and not the others. Also, a black film covered my finger tip.
It depends on the location of the vacuum source as they may be beside each other but vacuum source differ
raise the rpm and check if have vacuum you should.
Some vacuum leaks are very hard to detect and a special smoke machine is used to look for it
some shops charge about $ 85 to do the smoke test
check MAF sensor also in some rear cases may give you a lean code
do a fuel pressure test
check for a faulty or clogged fuel injectors