Tbi running rich and low idle problem

[Burbdood 74]

Hey all!
I've got an 88 Suburban with a TBI 350 and a swapped in TH350 trans. I'm not having a "problem", but I've noticed that the drive idle is rough and it's running a little rich. I've pulled the plugs and they look great, and I've replaced the O2 sensor with no change. The computer isn't throwing any codes and I don't have any driveability issues, but it's bugging me none-the-less.

The P.O. took out the AIR pump and removed the catalytic converter and left one of the vacuum lines unplugged. When I went to plug it, the engine was searching for a steady idle. I unplugged the vacuum line and it runs like before. Like I said, it doesn't throw any codes and it runs like a champ at all speeds. Am I just being anal or is there cause for concern?

 

[Burbdood 74]

One thing I forgot to mention. When I start it in the morning, it runs good at "choke" idle and once it warms up, the idle comes down. I've checked the timing and it's spot on at 0*. Could it be temp sensor?

 

[eagle mark]

I've seen a good running TBI 350 smell a little rich now and then without a cat.

But I'm not sure there's a vacuum line you can do away with? Which one is not conected at the TBI unit?

Why it idles better with a vacuum leak can only lead me think it has an IAC problem.

 

[Burbdood 74]

It's the vacuum line that goes in the back of the AIR injection valve to the base of the throttle body.

 

[British Slave]

Check the gasket under the TBI.

 

[Burbdood 74]

Check the gasket under the TBI.

I thought if it was a bad gasket, it'd cause a high idle 'cause it's letting in too much air.

 

[British Slave]

I thought if it was a bad gasket, it'd cause a high idle 'cause it's letting in too much air.

Just throwing out things I have run into. Mine was running rich (at least smelled that way) till I replaced the gasket under the TBI.

 

[dyeager535]

If that is a vacuum port, plug it, and then solve whatever problem crops up from plugging it. No engine runs *correctly* with an uncontrolled/unanticipated designed vacuum leak.

 

[Burbdood 74]

Just a quick update:

It turns out that the EGR valve had a pinhole leak in it. I took it out originally to clean it last week and noticed that even with the vacuum port plugged it sounded like air was leaking out of it somewhere when you pushed on the diaphram.

So, I went to the stealership and bought a brand new AC Delco valve, put it in this morning and now my idle issues are solved and it smells like it's running cleaner too. Oh what a glorious day.