Air hose from exhaust to intake?

[RonD]

Those numbers look OK, but...............

The flickering needle at 2k is a bit troubling if engine was just rebuilt, could be EGR or PCV but most likely valve issue
You can disconnect vacuum hose from EGR valve and plug the hose
Same for PCV Valve
But not at the same time
To see if either effects the flickering needle

2.9l uses a MAP sensor, this sensor uses Vacuum to tell computer engine Load, so Vacuum is a bit more important in your system than in say a MAF system because its a direct air/fuel control

It might be a good idea to put the vacuum gauge inside the cab where you can see it and "go climb a hill", lol
Vacuum gauges were used for years on the dash of many vehicles, best function is MPG, highest vacuum at speed is best MPG
But can also tell you of issues with engine functions

 

[dirtymike]

I'll do those test and see if the needle settles down a little. It doesn't deflect no more than 1/2 lb one way or the other. Bottom end hasn't been down,that i know of, just the top end. Been in the family since i can remember. Dirty

 

[scotts90ranger]

Engine will start to ping/knock under load if its running low on fuel
So if you don't hear that then its not a fuel issue

But..............I think 1987 2.9l had EGR valve and a Knock sensor, and the knock sensor could be detecting ping/knock and advancing the spark timing causing the drop in power
So it is a low fuel issue, lol, or low EGR flow
Its one of those chicken and egg things

Start with vacuum gauge to see overall engine condition, one of the better tools for diagnostics on "pumps"
And that's all any gasoline engine is, a self powered air pump
I like these tests: https://www.gregsengine.com/using-a-vacuum-gauge.html

Not to nitpick, but knock sensors retard timing not advance timing...

 

[dirtymike]

Did the test one at a time, pcv did nothing and the "EGR" test the small needle deflection stopped and was steady at 21. There are two vacuum hoses going to the EGR valve.

 

[RonD]

For which one?



You can't use the word any more, but yes, spark timing is differently challenged if Knock Sensor is activated by the sound of knocking

 

[dirtymike]

Does the 1987 ranger XLT 4WD 2.9L have a Knock sensor?

 

[dirtymike]

no