running issues

[richard meier]

sorry for not posting any updates in a while i am 69 now and having some health issues, the truck is running much better but if shut off hot it will still stumble twice on restart then run fine after that, I am wondering if being that almost all 78000 miles on it were at 25 miles an hour if maybe my catalytic converter is plugged and that would explain the stumble and low vacuum readings I get?

[Salvagedcircuit]

What engine do you have? In terms of vacuum readings, check all your vacuum fittings. Assuming you have a renix 4.0L, start with the easy to reach ones first: The fittings on the air box, the vacuum cluster in the front of the engine bay and those that go to the valve cover. The rubber fittings on the valve cover can crack over time. The new ones can stretch over time. I had to add heatshrink to mine because the dorman rubber elbow stretched. Check the vacuum line that connects the brake booster to the intake manifold. There is a hard plastic vacuum line that runs along underneath the firewall seam. This terminates into a rubber hose that connects to the evap canister by the passenger side rear of the engine bay. Mine was so dry-rotted that it turned to dust when touched. I replaced it with heater core hose. Also, check the EGR valve, it could be plugged up.

[richard meier]

i have the 2.5tbi in my 86, warm engine I have 12 lbs high revved I have 18 lbs I wonder what normal is. thanks for the reply.

[eaglescout526]

17 minutes ago, richard meier said:

i have the 2.5tbi in my 86, warm engine I have 12 lbs high revved I have 18 lbs I wonder what normal is. thanks for the reply.

 

If this is fuel pressure. 15psi is where it should be. 
 

I’ll look in my TBI book but I know the regulator should have it at 15 at idle. 

[richard meier]

my original question was about a plugged catalytic converter ,those were engine vacuum readings not fuel pressure.

[eaglescout526]

Isn’t vacuum typically read as hg? And not as psi. 

[pizzaman09]

A plugged catalytic converter usually manifests itself as a stumble when cold until it warms up.  Usually you can smell a heavy exhaust/raw gas smell.  In extreme cases the catalytic converter will glow red hot when it's plugged.

 

Sometimes the internal element will rattle loose and get plugged in the wrong orientation.  Hitting the converter will result in a rattle if this is the case.