Mechanic gave up 93 3.0 rough idle/ hard start

[Nate4570]

Working on dads 93 ranger 3.0, his mechanic couldnt figure it out so now its my turn and Im stumped.
Hard starts, stumbles and stalls the first time, once its running its shaking and stumbling. Smooths out if you rev it up, but something is knocking down by cylinder 3.
Fuel pressure running is between 35-40, new IAC, new O2 sensor. No vacuum leaks, plugs look good. Distributor physical timing with plug disconnected is 10 degrees advanced, with connector in computer takes over. Cylinders all have good compression and leakdown test didnt show a leak anywhere.

 

[franklin2]

What are your compression numbers?

What you could also try is get it warmed up and idling, and then get a glove or something and pull each plug wire off one at a time. See if it is particular cylinders miss-firing or is randomly all of them. If pulling the plug wire off makes little to no difference, you know that cylinder was not contributing.

I would also put the fuel pressure tester back on it, run it till it has around 40 psi, and then cut the engine off. Watch the fuel pressure gauge. If it quickly falls, you have more testing to do. It may end up being clogged injectors. We just had a post today about someone using some stuff they bought in the store to help them pass emissions. It looks like a very strong fuel system cleaner.

Here's the stuff he used. https://www.duralube.com/products/severe-fuel-system-cleaner