1987 Gmc Full Size Van/truck Idle Problem, Need Help! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 02-01-2011, 02:29 PM   #1
Senior Member
Posts like a Supercharger
Thread Starter
 
viniepooh's Avatar
 
Join Date: Dec 2010
Location: MIchigan
Posts: 177
Thanks: 0
Thanked 1 Time in 1 Post
viniepooh is on a distinguished road
Default 1987 Gmc Full Size Van/truck Idle Problem, Need Help!

Hi guys, I need your help, so every once opinion is appreciated, and thanks ahead! I have 1987 GMC G20 series 2500 Vandura, with 305/5.0L TBI and 400HD THMatic transmission, full size van. The truck starts just fine, but idles at somewhat higher RPM range as it should (even warmed up), around 1000. It would idle steady but then all sudden as if someone is pulling a life plug on it, or should I say turning of its ON switch, it begins to shutter, shakes, puffs, basically all sudden begins to struggle to stay up, and eventually usually would choke on itself and die, with check engine light on. Code 33, High MAP voltage, low vacuum. It will start right away again w/slight backfire, since It was just chocked on gas, idle another half min and die again, or sometimes what it does is after all that struggle that usually lasts about 30sec to a min, it comes alive j/as fast as it begins acting up and then would idle again w/slightly high RPM but steady for another min or so, then does that struggle thing all over again and usually stalls eventually with same Code 33. The truck is in our fam for over 18yrs. When it runs it runs gorgeous. We have rebuilt its engine about 3yrs ago, so it only have 6k on it, with RV cam, rebuild heads, pistons, rings, bearings and all thatů! Its TBI was also rebuild, along w/its manifold which was steamed and blown off from inside out. About a year ago we had similar problem w/it, and at that time after testing various systems I found the problem which was MAP sensor acting up. Right now as I type to you, the engine already have been given new MAP sensor, set of spark plug wires, spark plugs, distributor cap and rotor, ignition module. I have replaced all these in process of searching for a problem, as I have life time replacement on those parts anyways. I have also checked its compression to be sure that its mechanically sound, and it pumped out on average 5% below stock # which I believe is awesome, all cylinders pushing 168-175 on me. The reference Voltage of 5Volts is also there at all the sensors, including MAP. Engine pumping out 20mEr of Steady Vacuum on idle. Distributor is not loose, so I have not yet tried to re-adjust timing since it was all set up nicely last time before the problem occurred. Guys, im a little stumbled on what should I do or look at next, so please, any of ur advise is highly appreciated. I can tell u that I have not entirely checked everything, I think I left out IAC, and TPS which I will look into shortly, however if u have any suggestions to what you think I should do next, please let me know. Thanks!
Attached Thumbnails
1987 Gmc Full Size Van/truck Idle Problem, Need Help!-1987-gmc-vandura-2500.jpg  
viniepooh is offline   Reply With Quote
Old 02-01-2011, 02:38 PM   #2
Senior Member
Posts like a Supercharger
Thread Starter
 
viniepooh's Avatar
 
Join Date: Dec 2010
Location: MIchigan
Posts: 177
Thanks: 0
Thanked 1 Time in 1 Post
viniepooh is on a distinguished road
Default

Sorry for bugging you guys w/problem in regards of the Truck, i know its Bonnie forum, but ppl at GM truck forums over at other websites are kinda dead, no help there, and i know that u here specially some of you are always very helpful. Thks ahead.
viniepooh is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
1987 Gmc 350 No fuel NC124278 GMC/Chevrolet Truck/SUV 1 03-13-2014 02:48 AM
Foaming Coolant '79 GMC van kaylak General GM Chat 2 01-13-2014 07:57 PM
2000 full size van transmission wire harness pinout? 777funk GMC/Chevrolet Truck/SUV 1 06-13-2013 08:01 AM
1987 GMC Oil Pressure Gauge Pinned Doonjon GMC/Chevrolet Truck/SUV 3 10-14-2011 10:51 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 12:56 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.