I hope this the right area, but I have a 95 f150 with a 302 and it had eratic idle, it would rev up to about 1200 or so then down constatnly. I replaced the tps and no change so I cleaned the iac and it got better and had a normal idle till i drive it, when I slow down and put the clutch in it would drop and damn near stall, then come back to normal. pulled the codes and on the run test i got 412 and 538. any ideas? I dont know what 538 is. any help would be great.

 

412 is the idle speed can't be controlled. I suspect a faulty iac valve. You said it got better when you cleaned it. Have you checked fuel pressure? Checked for any vacuum leaks? If you search your problem a little, you will find very helpful answers to questions similar to yours. If not, repost and we'll help you out.

Robbie

 

I did check the pressure regulator and it seemed fine, I have not checked for a vacume leak though. one of the reasons i'm thinking a bad iac, is bacause when i'm driving it runs great, and never misses a beat.

 

How old is the fuel filter and the oxygen sensors?

SL

 

fuel filter is about five years old and oxy. sensor is original I believe.

 

Oh. Sounds like it's high time for a complete tune-up with O2 sensors, and a seafoam top engine clean. Not preaching here, but it's easier to track down problems when everything else is in order. You'll probably get a few who say that oxygen sensors never have to be replaced if they aren't throwing codes or the scope says they're cycling OK. If that's the type of advice you want to take, don't replace anything, ever. Bottom line is, they DO wear out. They DO get built up with deposits. They should be replaced periodically, preferably every 50-60K miles. You say it never misses a beat. That's great, but it'll probably run even better with a good go through.

SL