LeRoy90laredo

anybody know if a bad egr valve can cause the same symptoms as a missfire? I have checked all the plugs and plug wires, no crack in the distributor cap(which was replaced just under 3 months ago)

the problems doesn't always happen, sometimes it does, sometimes it doesnt. but when it does happen, the RPM's jump all around the tach. for example, the needle will be at 2100 and then jump to 2800 and then back to 2500, not in a fluid motion but in an instant jump.

ive also read ont he Ford Ranger forums that you can unplug and cap the EGR valve with no repercussions, anybody know of this?

thanks in advance.

01cherokeexj

I'm almost positive I read on another thread that our jeeps don't have an egr valve

tjwalker

1990 does have an EGR. But the symptoms you describe don't really sound like it. Here is information on the EGR. I would also test and adjust your "throttle position sensor".
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TESTING EGR VALVE

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.

cruiser54

I would be doing a good ground refreshing on this Jeep and maybe adding a ground cable from the negative battery post to the chassis. Ditch the braided strap from the back of the head in favor of a cable from the firewall to the rearmost bolt of the fuel rail.

StokeyBob

I've had the same sort of symptoms and found it was a vacuum leak somewhere in the vacuum harness.