Originally Posted by JESSE98ZJ
Hello, I am Jesse!
I am new to the forum. I found what seems to be an amazing deal on a 1998 jeep grand cherokee Laredo 4.0l. I found this really clean rust free ZJ up for sale for $600 it needed door pins and the engine was randomly stalling at stop lights. I bought it to repair hoping that it will be an easy fix and if not I can still get most of my money back so it is worth the gamble. So I bought it and drove it home on a 45 minute drive and it ran and drove perfectly, actually it was one of the smoothest vehicles I have ever driven. the next time I drove it about 5 hours later It started doing the stalling at stop sign thing. At stop signs it will shutter at low RPMs and then stall at really low RPMS. If you keep your foot on the gas and keep the RPMs above 1000 it runs fine. I have done some research and people that have had similar problems say it could be any of the following:
Crank Position Sensor
distributor cap,rotor and wires
Torque converter/torque converter clutch
Transmission solenoids/ Speed Sensor
So far I have replaced the Idle Air Control valve and the Throttle Position Sensor. I have checked some lines and fixed some possible vacuum leaks. I want to know if anyone has had a similar issue and knows what could be the most likely solution. Before this zj I had a v8 and it had the same issue with a different engine and I changed multiple sensors and never got rid of the issue before I got rid of it. The odd thing is that in park the jeep will run well. Sometimes in park the rpms will increase and sometimes it sounds like it will miss but it will never stall. Sometimes (rarely) the jeep just runs great, no stalling or anything. I have to think the engine isnt crap because it runs well over 1000 rpms and whenever it doesnt feel like stalling. Please someone help me before I spend too much money fixing this issue which will ultimately make this a bad deal.
I'd check the CPS. You should be able to get a Factory Service Manual from TechAuthority or eBay for how to do so, or watch for Frango answers.
You left off fuel pressure regulator and O2 Sensors and Catalysts.
There is probably a reason for the $600 price--they usually go for at least $1500 or more.
If you were in Los Angeles, I'd suspect crappy gas, or that stuff they sell as gas.
Pick up a scan tool and see if it would be kind enough to leave any fault codes that could narrow it down a bit.
I'd also run a can or so of Seafoam thru it in case the valves are all crudded up. That engine needs to be run to roughly 3500 every now and then to have the valve rotation work.