mine does that sometimes. especially uphill. sometimes it sorta stalls for a second and kicks back in

 

Yes, one of the most noticeable? problems is coming off idle. as soon as i touch the gas pedal, it's almost like the engine groans just for a second. Like the vacuum advance doesn't work. I replaced what serves as the computer, it's existence btw came as a complete surprise to me. It is mounted inside the driver's side fenderwell behind the battery. It has one big bunch and one medium sized bunch of wires plugged into it, and a vacuum advance diaphragm attached to it. At this point, I have absolutely no idea what this thing controls, other than the spark advance to the distributor. If anyone can offer any information, I would appreciate it. The only reference to it in the Haynes manual is how to remove and replace it, which requires the removal of two (2) 3/8" bolts. I plan to spend my weekend mapping and replacing every vacuum hose on it and removing and capping the ones I no longer need.


This would be a good time for me to suggest to everyone that reads this to take reference photos of your engine compartment even if you don't have any repairs planned. I took several " berfore" pics shortly after I bought it and they have been invaluable. Thanks for the help. Please keep the ideas coming.

The timing is set at 8 degrees bfore tdc, which is factory spec.

 

i thought i had a vacuum problem but i ran a gauge into the cab and all seems well

 

I said I would keep you posted so here goes. The discovery of the computer led to the discovery of a diagnostic port. I have a friend who owns a shop who has a scanner that worked on my truck. No new information was learned but it was cool to know my truck had on board diagnostics. I did learn that the vacuum hose that ran to the spark advance on the computer had no vacuum, it was routed to the wrong spot. It was then I took my Haynes manual and mapped every vacuum hose and found a few other things to be misplaced. Though it ran much better, I still had my stumble. I removed the distributor and discovered the air gap was set a whopping 17 thousandths instead of the recommended 5.

That was MOST of my problem, the truck runs much better now, but I need to re-set the timing. I now realize I was trying to find one solution to fix all of my problems. That won't happen again.

Truck and owner are once again on speaking terms and I learned a lot that I didn't know.

 

youll know when the computer has something to say when the check engine light comes on.

 

It doesn't have a check engine light. Which is one of the reasons the computer was such a surprise. I now have a schematic of the computer so I'm learning all kinds of new stuff. I found out last night that one of the nuts on the coil was stripped and the leads to that side were loose. Today I will fix that. After all the mistakes I have found, it's a miracle it was even running.

 

now that i think of it, these trucks didnt go TBI untill '88. yours must be an oddball

 

I agree, 87 was the last year for carburetors, so I'm kinda stuck in between.

 

There is a light that comes on every 40,000 miles or so on the 87's. I believe all it is for is a reminder to get the emissions checked. I took the bulb out of mine. The computer behind the left head light is the last version of the lean burn system from my understanding of it.

 

oh. i knew there was the sprak conrtol computer. but i dindt think anything with a diagnostics ports