Very rough idle!

[roadhawg]

A few months ago, my 99 Ranger developed a slight surging during idle. I found a loose o2 sensor bung on the cat so the cat was replaced. I also replaced the gas cap since it is 12 years old. I thought is was better until about a month ago, it started really idling rough at start up. I replaced the IAC today with no improvement. My scanner has been reading P1151 but today it just showed Err. I hate to have to replace every 02. Any educated ideas?

, I looked and couldn't find a search button for this subject.

 

[bigdan002001]

Check for vacuum leaks....

Dan

 

[roadhawg]

Do you have any suggestions where to look.

 

[bigdan002001]

I would suggest either a haynes manual or chiltons..... Is your truck 4x4? If so, then do your pulse vacuum hubs work properly? Because vacuum leaks sometime generate from this issue as well since you have a 99. Locate the multi-tap connector on the intake manifold and follow each hose to it's respectible locations and check each one. You can use a can of starting fluid and spray around hoses and if idle speed increases, then you've found your leak. There is a small hose that connects to bottom of throttle body that is hard to see and often gets overlooked as well. Hope that helps?

Dan

 

[bigdan002001]

Forgot to mention the one that was leaking on my truck was line from fuel pressure regulator to the passengers fender well where black plastic ball is located...it's a vacuum canister...mine was leaking at an inline connect that someone had put in the middle of the line due to breaking apparenty and it was very loose and losing all my vacuum causing very poor idle and lean code conditons.

Dan

 

[roadhawg]

I think I found the problem. I sprayed some starting fluid on the small part with vacuum lines in front of the passenger front tire and the idle would raise. I just spent 20 minutes looking at the tech section for vacuum issues and for a diagram for this part to see what it is but no luck. Anyone here have a clue?