87 waggy/4.0/4wd

Morning all:

The engine is loping at idle. Per the vacuum guage, it's not a leak. New timing chain, TPI (adjusted), IAC, MAP, plugs, wires, O2, cap and rotor. Grounds are refreshed, clean and tight.

Intermittent high idle, but that seems to have abated since I lubed the throttle spring.

While at idle there is a lope. When I depress the peddle, it bogs and then if I don't let up it backfires.

Gas mileage is miserable and there's no power on an incline- even a minor one.

Thoughts?

 

That should read TPS, not TPI, and it is adjusted correctly.

 

sounds to be running lean or rich, check your fuel pressure with a gauge.

Maybe a failing pump, clogged filter, bad ballast etc.

 

Fuel filter has been replaced. I don't believe there is a ballast on my Jeep, at least there'snot one on the fender by the air filter.
Fuel pressure is 32-34 per gauge and 42 with FPR vacuum line removed.

Had it in the muffler shop on Friday, per them, it's not a bad cat, restricted flow or leak.

Any thoughts on what to check next would be greatly appreciated.

 

Lopey idle, low power, bad MPGs, it's the EGR system.

 

EGR is a possible vacuum leak which can't be detected by spraying with liquids.

What is your vacuum reading?

Is your O2 sensor plugged in or have you ever replaced it?

The hose/line to the MAP can wreak havoc also. Make sure it's not cracked or loose at the ends.

Did you adjust the TPS on the engine side, flat 3 wire connector?

Ever cleaned the C101 and done a sensor ground test?

 

And also instead of sucking in regular air it's exhaust fumes

 

TESTING THE EGR VALVE FOR 87-90 4.0 ENGINE
Valve Opening Test
1) With engine at normal operating temperature and at idle,
rapidly open and close throttle. Open throttle sufficiently to obtain
at least 1500 RPM. Movement should be noticed in EGR diaphragm.
2) If diaphragm does not move, probable causes are: faulty
vacuum signal to EGR, defective EGR diaphragm or defective
backpressure sensor diaphragm (if equipped), or leaks in vacuum lines
or connections.
Valve Closing Test
1) With engine at normal operating temperature and at idle,
manually depress EGR valve diaphragm. RPM should immediately drop,
indicating that EGR valve is not leaking and had been properly cutting
off exhaust gas flow at idle.
2) If there is no change in RPM and engine is idling
properly, exhaust gases are not reaching combustion chamber. Check for
plugged passage between EGR valve and intake manifold.
3) If engine idles poorly and RPM is not greatly affected by
manually moving diaphragm up, EGR valve is not closing off exhaust gas
flow. Check for carbon between pintle, leaking EGR valve gasket or bad
EGR valve.
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