TBI bogging?
 

I have an 87 GMC 350 TBI. I recently just put a mild cam in it. The first day after putting in the cam it ran great and did not hesitate at all. Now about 3 days later the truck is bogging when you accelerate and it has a pop and or skip in it.

The timming is right on 0. and i just put new spark plugs in it today. The other plugs were very black.

anyone have any ideas to fix this?

Re: TBI bogging?
 

try advancing the timing a few degrees

-Jake

Re: TBI bogging?
 

I had the timming advanced and it did the same thing.

Re: TBI bogging?
 

Check the TPS.

Re: TBI bogging?
 

What is the tps?

Re: TBI bogging?
 

throttle position sensor

Re: TBI bogging?
 

where is that sensor located?

Re: TBI bogging?
 

Now when you hit the throttle at all the truck just pops and skips and sometimes backfires.

Re: TBI bogging?
 

Is it throwing a code? What's your fuel pressure? I know you stated it ran fine when you first ran it, but how big of a cam is this? Did you get a new chip burnt for running this cam?

Re: TBI bogging?
 

it is not showing a code, and i am not sure what the fuel pressure is. But the cam is a .444 intake and .466 exhaust over a duration of .50, it is a mild cam. the truck is already chiped but not for this cam.

Re: TBI bogging?
 

Today i am going to adjust the lifters yo see if that doe anything.

Re: TBI bogging?
 

when you set the timing did you disconnect the brown timing wire?? I know on my '88 it ran like poop until we did that.

Re: TBI bogging?
 

What do you do with that wire and where is it located? Someone told me today that there is something that i have to do before I time it, but he told me that it has to do with the OBD I and not a wire

Re: TBI bogging?
 

there is a brown (I believe) wire between the brake booster and bulkhead connector that needs to be unplugged before you set timing. that takes the timing control away from the computer

Re: TBI bogging?
 

I just looked and the only brown wire that i saw was in a connector of two of them. Would that be the right one? because it is between the booster and the motor. And what is the bulkhead exactly?

Re: TBI bogging?
 

The bulkhead connector is where the wires go through the firwall to the fuse block.
Should only be one wire. Might be tan instead of brown.

Re: TBI bogging?
 

Alright tomorrow I am going to try to find it and time it the right way

Re: TBI bogging?
 

http://i185.photobucket.com/albums/x...7/DCP_1924.jpg
I found this on here....
White arrow is pointing to the connector. Tan wire with a black stripe

Re: TBI bogging?
 

Thank you. hopefully i can get to it tomorrow. That picture really helps.

Re: TBI bogging?
 

no problem ;)

Re: TBI bogging?
 

Not pulling that wire before setting timing will definitely cause wrong timing! Of course remember to hook it back up after timing it. Shut the truck off though before you re-connect or disconnect that wire, atleast that's what I do.

Re: TBI bogging?
 

well hopefully that whats happening right now. tonite i am going to try to fix it along with the tps and the temp sensor. thank you for the help. i will post what happens tonight.

Re: TBI bogging?
 

HEY! That picture looks familiar?

Re: TBI bogging?
 

somebody stole it!
:haha:

Re: TBI bogging?
 

on my 88 you had to remove a plastic cover over the fuseblock and there was a tan wire with a connector, running toward the brake booster. disconnect it, time the truck, restart and voila!! yeah its like 15-20 degrees retarded if you dont do that, even worse with a cam, lol.

Derek

Re: TBI bogging?
 

i unpluged that tan wire and the truck would not start. There was no gas going in the throttle body.

Re: TBI bogging?
 

Hmm, maybe the wrong wire? I remember on my 87', the wire being tan with a black stripe. You had to look real close. I'll double check mine and snap a photo if you'd like. One was already posted I see but I could snap one a bit more detailed.

Re: TBI bogging?
 

I changed the the tps and the temp sensor and it is running better but it is still using to much gas.

Re: TBI bogging?
 

if you removed the distributor and set the timing without unplugging that wire, the timing is wrong. no matter the other issues, you definitely need to address the timing. heres a link for ya

http://westersgarage.eidnet.org/Set%...structions.pdf

Re: TBI bogging?
 

thanks i will give it a try this weekend at some point

Re: TBI bogging?
 

I did and it works, but when you connect the cable, the problem returns, if you do not connect my check engine is permanently lit...
I kept it off temporarily...

starting the engine keeps running, but to reverse or drive and motor cutting out...

I can do, help me...

Re: TBI bogging?
 

The "westergate" link is wrong about one thing, The timing conector is in the harness is on the firewall as pictured in this photo. not over by the blower motor . I'm not sure what you are disconnecting that is making the engine not start. My guess is that you are running now with the engine in "Open-Loop" mode which are the ECM presets. The problem with this is , it does not use any sensor input when warmed up. So your fuel curve, timing and idle speed are not being fine tuned. If everything is working as it should , a TBI engine is a dream to drive.