Well I traded my 76 for this truck, mistake #1. Day after I bought it the FPR went out, replaced it with the plenum on. Still ran bad but it was high idle now, replaced the missing plenum gasket, not it bounces off the rev limiter at idle. I've replaced the throttle body gasket and the idle air solenoid, I know for a fact everything is hooked up and the timing has never changed. What the hell is wrong with it, I dont know. What do you guys think it is? What's this things scrap value or part-out value? It's a RC SB with an Inline6 and an m5OD. I'm tired of working on this POS for it to run worse. I have very little money as I'm a high schooler and I'm fixing a 77 highboy that was wrecked. I never planned to keep this truck but it looks like I'm going to keep it for a lot shorter than I expected.

On a side note, anybody want a parts truck that's located in plant city Florida? Will not deliver and make offer.

 

I would say its a fair chance you have a vacuum leak somewhere.

Since you replaced the fpr you were working in the area where the pcv hose connects to the intake manifold. I would say you knocked it off as a guess.

On the '88 truck I have and the '89 parts engine the pcv hose connects to the underside of the upper manifold roughly in the center.


If I were you however I would fix it, these trucks run forever with minimal maintainence once you get them straighted out.

 

Worst comes to worse you always have the option of a EFI to carb swap.

 

I would recommend Checking for vacuum leaks and pulling the codes even if the CEL isn't on. The ECM might be bad.

 

Don't give up, I would do as suggested and check for vacuum leaks. Check ALL of the lines, not just one's you've worked on. Also if you have any unused vac ports that are capped off, check the caps on them. I found a few on my truck where the cap crumbled in my hand when trying to remove them.

The parts store has vac caps for maybe $3 for a box of assorted sizes.

 

While that is an option, there's barely any sensible reason to suggest that as a good option.

Given that you're in FL (i.e. heat-land), I would definitely pull the PCM and open up the case to see if you have any leaking capacitors. This is an ever increasing problem as the components age, and heat only further accelerates the break-down.

 

Me and my grandpa played with it for an hour, adjusted timing, unplugged ALOT of stuff and plugged it up again, and its running better but he says there's a leak in the plenum. Ill have my dad check it out when I'm at school tomorrow. If I don't get it fixed I'm trading it for a set of 37" militaries, I'm just so fed up with it.

 

You can spray carb cleaner or water around the intake and if the truck gains rpm's or stalls you got a intake leak.

 

Is it possible the 02 or whatever other exhaust sensors is bad?

 

Possible, but highly unlikely that's your problem. Have you checked the PCM like I suggested? Have you pulled error codes? Have you fixed your reported vacuum leak?

 

I fixed the leak we found, bolts were just barely too loose. Where is the PCM?

 

It's located behind the driver-side kick panel. You'll unbolt the harness quick-connector from the engine bay with a 10mm socket.

 

Ok we'll look for it next time I've got time