8.1 Mods Made, Now Problems..Help!

Harpoon · May 13, 2005

Hello All: Newbie here... great site by the way!

I need serious help!

Own a 2001 Suburban 8.1 liter 2500 automatic with 75k miles.

Had rattling exhaust system so had reputable performance shop install the following which I bought for performance upgrades:

Gibson headers with two generic cat converters (round) into a single flopro dual in dual out muffler. Old had two also.

Used the original 3" pipes from headers collectors to first cat converter then new 3" pipes from there to other cat then to muff.

BBK 80 mm throttle body and K&N air filter.

Installed per procedure twice letting coumputer re-learn at start up and driving. Works fine at start up but after driving and at stop lights idle drops to 400 ro cuts off (oil pressure drops to 0 and no oil warning comes on)

What can I do to find problem? Called BK and told to adjust set screw, but it appears to be computer will not learn new equipment, headers have 02 sensors installed, electronic throlttle (no cable) and no egr on this model.

Help! Dont know if "back pressure" is messed up I read about or should I use super chips type programmer to try and change settings? HAVE not drove for over 100 miles only about 35.

Any help is greatly appreciated!

Harpoon

SS Crew · May 13, 2005

Did you try disconnecting the battery for about 10 minutes to allow the computer to "reset" to the new mods?

Haulin' 8.1 · May 13, 2005

It's not a back pressure issue. Unless the 02 wires are completely screwed up, like melted through and grounding on the exhaust, then exhaust shouldn't be an issure.

It's likely that your throttle closes to far for a base idle speed. Have you actually tried to adjust the throttle stop set screw yet? By the way it reads you didn't specify, like you think it's the computer so you didn't try it.

Another possiblitly is a throttle posistion sensor that is out of adjustment. I've yet to have to work on one of those electronic throttles yet so I'm not exactly sure how it's designed but say that the PCM thinks the throttle is a 4% when it's at zero you'll have this problem.

Vernon

Harpoon · May 14, 2005

Thanks Vernon and SS Crew for posts:

Mechanic ran for 10 minutes per instructions at idle with no interferance. Then...

I went through and unhooked both batt cables (turned lights on to drain system) that night to re-set it and left batt cables off over night, hooked back up, and ran for twenty minutes per BBK tech service help guy on phone.

Instructions say that some may require 50-100 miles driven before computer learns everything.

Also, yes, there is supposed to be a position set screw I havent found it yet and is said to be under casting flush with base. Going to try and find and adjust tomorrow in daylight.

I think you are right about position of electronic motor module thing a ma bob. They took old one off and re-installed on new throttle body so it may be off a hair, but not sure how to adjust.

Anyone know that can help with this new question? I just bought new book on Chevys so might find answer there.

I just drove it again for twenty miles and it sure does have new found power and will "jump and go" now, but just decides to dip low in the rpm range at stops so oil press warning mess then comes on.

I appreciate the help, guys!

Harpoon

Raleigh, NC