TBI bogging?

[Kmart2352]

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?

[jake wells]

try advancing the timing a few degrees

-Jake

[Kmart2352]

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

[Jonboy]

Check the TPS.

[Kmart2352]

What is the tps?

[bigarmzz]

Originally Posted by Kmart2352

What is the tps?

throttle position sensor

[Kmart2352]

where is that sensor located?

[Kmart2352]

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

[chevymotocross]

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?

[Kmart2352]

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.

[Kmart2352]

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

[Trick76]

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.

[Kmart2352]

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

[joe231]

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

[Kmart2352]

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?

[joe231]

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.

[Kmart2352]

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

[joe231]

I found this on here....
White arrow is pointing to the connector. Tan wire with a black stripe

[Desert1957]

Originally Posted by joe231

I found this on here....
White arrow is pointing to the connector. Tan wire with a black stripe

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.

[Kmart2352]

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

[joe231]

no problem

[chevymotocross]

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.

[Kmart2352]

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.

[Desert1957]

HEY! That picture looks familiar?

[joe231]

Originally Posted by Desert1957

HEY! That picture looks familiar?

somebody stole it!