I checked the 02 sensor on bank #1and I checked all the hoses for leaks and found no problem. I found a link that said the MAF could be dirty so I may check that out.


My engine idles up and down at the light and jerks the van but when I hit the pedal it runs fine but I still get the code back even when I erase it :PO171 running lean?

Sounds like the IAC is starting to go.

I found one at a junk yard and replaced it but still did the same thing, one of those would cost me $350.00 brand new and I almost fell off my seat when I heard that! I cleaned the MAF with some electronic cleaner but it did no good. I replaced the coolant sensor and still nothing, heres a site I been looking at on this stuff:


http://www.4x4wire.com/toyota/4Runner/tech/OBDII_ECU/

I tested theMAF sensor and it checked out ok, now I'm going after the fuel pressure regulator to see if it's stuck shut or open. I'm going to check the PCV valve if it functions or not.

another cause of a run lean is the spark plugs themselves. Once,a while back, the #1 plug on my 98 contour had a bent electrode pin and caused the lean issue.

what caused that? just a bad plug?

I also forgot to mention that when I start it up it idles fine but in between the warm up stage it idles up and down for about five minutes and then stables out. My spark plugs were changed and I tuned it up but still have the code coming up.

yes/no plug wasnt bad,just bent tip. restraightened and fine.