Boggy 4.0

Hello all, new to this forum and to the renix system. I have an 89 Comanche with the 4.0 and ax15. When I first got it, it wouldn't hardly run due a plugged cat. With that fixed, it idles well, pulls strong in the upper rpm range, but just off idle it is real boggy and smells rich. I have been told that retrieving codes is difficult on this system, but that sensor ranges can be checked with a multi meter. I spent nearly 30 years in suspension, alignment and brakes, but early (pre OBDII) fuel injection are not my cup-o-tea. Any help is greatly appreciated and will be paid forward.

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

http://www.lunghd.com/Tech_Articles/Fuel_System/Fuel_Diagnostics.htm

http://naxja.org/forum/showthread.php?t=1080727

All of the above articles should be helpful to you.

Good information from Mike.

Start with verifying fuel pressure and testing your MAP sensor.

For your 89, you should have 31 psi of fuel pressure at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be sure that the vacuum line is pulling good vacuum and is not wet with raw fuel, which usually indicates a ruptured fuel pressure regulator.

Factory service manual, (check ebay and link below) a meter and the ability to use both are essential with RENIX vintage XJs.

http://www.pacificcoastmanuals.com/jeep_cherokee_service_manuals.html

Good luck!

I had thought of checking the MAP and TPS first, guess I'm not too far off base, thanks guys, much appreciated

Read this on early XJ injectors:

http://www.jpmagazine.com/techarticles/engine/154_0811_preventing_jeep_engine_fires/

Check the vacuum line on the FPR for a fuel leak. Check the GROUNDS on the sensors!!!! They use a spot on the engine block near the oil dip stick. Poor electrical contact there causes many problems. O2 sensor problems can make it run rich. Check the spark plug gaps, spark wires, and rotor and cap!!!!