very rough idle/stalling out

1990 renix 4.0

so i have never had a problem with my jeeps engine before this and the iac sensor when i first got it. the problem started a day ago after i had just gone wheeling. My idle got very low and was stumbling really hard... it has gotten worse so now i have to free rev it to keep it going. I originally thought it was a miss but i have replaced the plugs,wires,cap and rotor the only thing not replaced is my coil. I have good fuel pressure and have changed my fuel filter recently. I am so lost please point me in the right direction.

thank you

Check the EGR system.

what exactly would i be checking and why would that be a problem?

Bad EGR effects air/fuel mixture. Your renix also has a vacuum transducer valve (89-90 only) that likes to get agaisnt the exhaust manifold and burn up--$90 at the dealership, $5 at the salvage yard, when you can find them.

Also check the MAP sensor on the firewall.

so does the transducer valve and the egr get replaced for 90$ and would i just check the voltage with the map sensor?

so after doing more searching i have narrowed it down to the crankshaft position sensor or the egr system. Does that sound right?

Usually CKP crank position sensor works or it doesn't. Bad EGR could act like a vacuum leak. I'd check the EGR. Plug it off and see if that fixes the idle. If it does, fix the EGR.

ok where do i plug the vaccum going to it, is it at the round plastic thing inline with it or at the actual valve? and what about the camshaft positioning sensor would that screw things up?

Don't know on your model. It must run from the exhaust manifold to the intake manifold if you can disconnect it and plug it on the intake side. The exhaust may be noisy, but this is just a temporary test. When the CKP stops working, the ECM/PCM shuts down the "latch" relay which controls spark, injector, and fuel pump power supply.

ok guys thanks a bunch! i love naxja! it was my egr valve...... i plugged it and it purred like a kitten. But i was wondering if i should clean it and go from there (worked for my iac valve) if i was to try it what should i use?

The round plastic thing inline with the EGR valve is the vacuum transducer valve, it has three vacuum lines to it, the one on the bottom is usually burnt off.

We fixed the EGR solenoid/valve on my kids old Mercury by taking it out, spraying it with brake cleaner, and working it back and forth by hand. Worked fine after that. If there is a pocket it seals in, clean that too.

ok thanks again i will get started on that. I probably should replace the gasket though.

so i tried cleaning it and it still is broken.... i was wondering if i could just fab up a small plate to cover the holes on the intake manifold and block the vacume hose going to it. I have heard it done in other vehicles as a egr delete. and yes i know it wouldnt be "smog" legal but i dont have to worry about that where i am at.

You should just replace the EGR.

No one knows what "Green" regulations are coming down on us.

Was going through trouble shooting on my GF's EGR valve and the easiest way I found to test it is check the EGR valve controller by unplugging the green plug on the vacuum controller on the drivers side of the engine bay next to the resistor. This then applies vacuum to the EGR valve and should open it letting in exhaust and causing it to sputter and stall. If there is no change I'd recommend replacing because even though they are clean those diaphrams can dry and crack rendering the useless. On the transducer you can use a small screw driver and open it up to inspect it, but on the metal one that is actually on the EGR not so much. From my understanding/experience the removal of the EGR means that there is less inert gas entering the motor meaning more fuel consumption. Another way to verify the EGR is looking up the error code. I believe there is one in there for EGR or no change in air/fuel mixture using EGR. Just some food for thought, I'm still checking on mine but one of the bolts is stripped so I'm deciding whether to try and elegantly remove and attempt cleaning at first for take an f-ing air saw to the thing and just replace. I checked my transducer and it looks brand new so I'm at a loss.

well i appreciate all the advice but i built a plate to block it off.... i live in redneck land and i get around 11 mpg with 33s and 3.55 so i am not so worried about gas. the way i see what i did it is 90$ shorter to my 4.88s. and it runs strong now. mabey even better before the valve broke!