The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Engine & Drivetrain

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 08-05-2017, 10:28 PM   #1
texastruckjunky
Registered User
 
texastruckjunky's Avatar
 
Join Date: May 2009
Location: San Antonio,Texas
Posts: 218
Question 91 Silverado TBI problems

I have a 91 Chevy 1500 with the 350 700r4 combo. having problem with black smoke coming from the exhaust. Pipes are cut off after the muffler so it's leaving a black residue all over the rear end. But that's not the problem, truck spits, runs rough and dies, it's hard to start after words. If I let it sit for 30 to 45 minutes it will start. It runs for a little while then dies again. I've changed the fuel filter, fuel pump and rebuilt the TBI. Now black smoke is coming from the exhaust. And it's even harder to start. I've done some research on the problem and from what I'm understanding, it could be a O2 sensor or the MAP sensor. Any help would be appreciated. Thanks.
__________________
Life is to short to drive anything else
texastruckjunky is offline   Reply With Quote
Old 08-05-2017, 11:18 PM   #2
edhtrd71
Registered User
 
Join Date: Jan 2011
Location: Edinburg, Texas.
Posts: 179
Re: 91 Silverado TBI problems

Hey, it sounds like its running really rich, which you probably already know. Definitely can be the o2 sensor or map sensor. It could also be the coolant temp sensor also. Quick checks you can make are checking the connections and related wiring to those sensors. Make sure the map sensor vacuum hose running from the throttle body isn't cracked and leaking. After that I would invest in a data reader so you can see what the sensors are doing. Also I have seen ignition modules cause funky drive ability issues on those. Good luck.
edhtrd71 is offline   Reply With Quote
Old 08-05-2017, 11:43 PM   #3
edhtrd71
Registered User
 
Join Date: Jan 2011
Location: Edinburg, Texas.
Posts: 179
Re: 91 Silverado TBI problems

Hey, it sounds like its running really rich, which you probably already know. Definitely can be the o2 sensor or map sensor. It could also be the coolant temp sensor also. Quick checks you can make are checking the connections and related wiring to those sensors. Make sure the map sensor vacuum hose running from the throttle body isn't cracked and leaking. After that I would invest in a data reader so you can see what the sensors are doing. Also I have seen ignition modules cause funky drive ability issues on those. Good luck.
edhtrd71 is offline   Reply With Quote
Old 08-11-2017, 10:53 AM   #4
88Ironduke
Registered User
 
Join Date: Jul 2010
Location: Willingboro, NJ
Posts: 458
Re: 91 Silverado TBI problems

91 TBI should have an ALDL port to check for codes. Granted its ODBI but if the map or O2 sensor is dead it will flash out a code. Make sure the vacuum line for the map sensor hasn't cracked and isnt leaking. Another fail that's hard to find is failing fuel pump relay, the old ones can quickly cycle on/off causing all kinds of havoc. It is the same as the AC relay and can swapped to eliminate systems.

Good luck.
__________________
Retired USAF - No rockets, no mortars, no bad guys shooting...No stress!!!

My Build Thread: Project 72' Green
http://67-72chevytrucks.com/vboard/s...d.php?t=587932
88Ironduke is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 07:47 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com