Help me get my k5 running again

[dheavychevy38]

I have a 87 k5 with a tbi. I had to park it for around a year or so but have fired it up and moved it around the yard a bit. Recently it has gone crazy on me. I put a full tuneup on it with all delco parts. The problem is that it has a small pop through the exhaust on accel. Then it was actting like it was flooding and would not run at an idle and die while black smoke out of the tail pipe. Now it will start and run and idle but out of the blue it will rev up to like 2000 rpm then back down then back up and so on. No check engine light has come on and yes I checked the buld. Please help. sorry for the long post.

 

[jekquistk5]

Sounds like a vacuum leak. But could be anything. Id start with vacuum leaks and go on from there.

Also I would put a new fuel filter and some fresh fuel in there.

If you do not find any leaks Id suggest tunerprort and a ALDL cable to see exactly what every sensor in your truck is doing.

 

[dheavychevy38]

I sprayed the intake with carb cleaner with no change to the rpms. Filters,fuel and pump are new.

 

[jekquistk5]

You could put a piece of cardboard over the top of the TBI to see if the IAC is still working. If it stalls out its bad, it could have some gunk in it.

 

[jekquistk5]

You can also measure the resistance of the two coils in the IAC

 

[diesel4me]

Does it have a fuel pressure regulator?...if so,the diaphram in it may have failed and that will let raw fuel get sucked into the vacuum hose and the intake manifold,and cause it to flood,run weird like that...

 

[DirtRidinz71]

Unplug the vacuum line off of the erg valve, I had one valve go bad and caused the truck to randomly rev up and down at low rpm. Also try unplugging the coolant temp sensor (one by the t-stat housing on intake), they are problematic and can cause of sorts of weird problems.