Engine stall and loss of power
 

Hi,

I have a mess I'm trying to fix. When I step on the throttle the engine quits for a split second and then refires. Sometimes while driving, it will stall completely. And then when you are driving down the road it just doesn't have power.

Info:
1996 4.0L V6
Engine was replaced 3 years ago(before me seeing truck) and has had the above issues ever since. Appears to not have been a new rebuild.
I only have knowledge of this truck for last 9 months.

So far what I have done:
It was throwing O2 sensor code on bank 2(driver side) lower by fuel filter before CAT. Replaced and code resolved
Also had EVAP code. I replaced purge valve, hose that was split and code cleared
I replaced the EGR valve and PCV valve.
I replaced oil, oil filter and fuel filter
Checked vacuum on back end of intake and it was 14 inches(I believe that is what the measure is called?)

No change. Before I started pulling off vacuum hoses the truck was throwing no codes. I had borrowed a OBD reader but he wanted it back. I have one arriving today to clear the codes I caused.

It seems to be leaking oil under the valve cover gasket and appears to be getting worse. I was told the engine isn't getting rid of pressure(exhaust) quick enough. Thinking about disconnecting the exhaust to rule that in/out.

Your thoughts? Any other ideas I can try/check?

Thanks, David

Welcome to the forum

You have a 4.0l OHV engine in a 1996 Ranger, 2001 and up Rangers used a 4.0l SOHC engine which is quite different, just FYI

Vacuum on an idling engine should be 17" to 20", so yours is WAY TO LOW
This could be from an exhaust blockage
OR
A VERY BIG vacuum leak which you should hear
OR
low compression, engine is bad

You can pull out both upstream O2 sensors and then start engine and test vacuum again
If its in the 17-20 range then yes, you have a clogged exhaust

You need to solve the vacuum issue first, that's your main issue at this point


Clean MAF sensor, once a year on any 4.0l OHV