vacuum leek? Or something weards?

[pyro]

Hey,
First off i searched around a little and cant find anything else specifically for this WEARD situation. Well any ways i was driving today and realized that gas was >3.25 a gallon. So i decided to check my mpg and i was getting 12.5 mpg! Then in a parking lot i am sitting in a parking space trying to think what is up with my car and just ever so slightly tap the gas and let go and the engine idle goes in a loop from 500 to 700 rpms and back. After further testing if i come to a complete stop in drive and just tap the gas the engine will do that indefinitely. So im wondering does this WEARD idle have to do with bad gas mileage. I was reading in other posts that when you have a vacuumed leek replaced intake boot check vacuum lines etc and everything looks ok unless there not sealing properly. I'm kind of at a loss because i don't know how to diagnose the problem.

[winfred]

the most common leak point on a m50 is the 2 lines coming off the valve cover, the little one goes to the fitting where the idle control valve connects under the intake, and the big one goes to the air boot, the line can rot off and the boot can split where the line connects. it's also possible that the idle control valve needs to be cleaned, i clean them with carb cleaner

[pyro]

i took everything appart accept the intake manifold and cleand out my icv and noticed where the icv plugs into the manifold that little slip in thing is VERY loose. It won't come off but it wiggles around. and i also noticed my intake boot is cracked pritty bad. not all the way through but it could be and i just don't kno it. but could a air leek in both of those areas cause bad gas milage-weard idle? The weard idle seems to have gone away but gas milage dind't change a bit.


EDIT also i noticed when my engine is running there is a VERY loud sucking noise. it seems to come from inside the intake manifold but im not to shure.

[632 Regal]

I think you have diagnosed 2 of your problems here:

noticed where the icv plugs into the manifold that little slip in thing is VERY loose. and i also noticed my intake boot is cracked pritty bad. but could a air leek in both of those areas cause bad gas milage-weard idle? (YES!) .

[pyro]

i think i may have found a third. searching through the forums i found that after repplaceing fuel injectors idle smothed out... I found a place that cleans your injectors for 12 each. Is that good for a car that has 170000 miles?