What kind of problems can a bad smog pump cause. I changed out all of my vacuum lines and my truck was running great. mileage went up and the truck ran smooth. my bearing in my smog pump was going bad, so i bypassed the smog pump. now my truck idles rough and surges. the mileage has gone down too. since i've bypassed the pump, do i now have a vacuum leak where the smog pump was hooked up? should i replace the pump or is there a way to reroute or plug the lines to make the truck run right again?

 

What year is it and is it tbi or full efi? And smog pumps aren needed really and the vaccuum problem shuldnt be the smog pump all my hoses are disconnected I just am to lazy to bypass the pump. And by the way mine is a 1992 4.9l EFI

 

It's an 88 F150 Fuel Injected

 

I've replaced all vacuum lines, egr sensor, tps, iac, map sensor and fuel pressure regulator. I've checked for leaks using spray. Didn't see anything that would lead me to believe there is a leak. Am I missing something?

 

What size engine? 4.9, 5.0, 5.8? And I can't seem to think of anything else that could be... Mine was doing that then I vapors the plug on my 4.9l to .045 and it runs a lot better.. I'd try that. I'm no expert on anything all I know is from experience and research.

 

Sorry I meant gapped the spark plugs

 

I'll try the gap thing. I just can't figure out what's causing the surging.

 

Check engine light on?

 

I'm not getting any CEL. I disconnected the IAC and the truck idles better. It's idling at a low rpm, but the surging has stopped. Is the IAC the problem? I just replaced it. Maybe I got a bad IAC.

 

It could certainly do that. Makes you wonder if the valve is sticking.