Yfz450

my girl friend has a 99 cherokee that's she is having some issues with. I don't know much about jeeps I have only had fords. Anyway while driving the engine will start missing and sputtering out of no where and sometimes stalls when it comes to a stop. It does it when it's warm and cold. I did a tune up a month ago to see if it would help but it didn't. When driving it will feel like it is missing all of a sudden and if you put the pedal to he floor it will stop missing. At times when it's missing you can hear it pop through the intake.we have taken it to 2 different mechanics and no one can figure it out. I know for sure that it's not a clogged cat, tps or 02 sensor so those can be ruled out. If anyone could help it would be greatly appreciated.

mitch500

That happend to my voyager. I replaced the plug wires and it was good to go.

I would do the following. Plugs,wires,cap/rotor

Yfz450

I did that with the tune up. It didn't seem to help any

mitch500

What kind of plugs?

Yfz450

I'm don't remember

pdowty68

Try resetting the ecu. Sometimes it helps after tune ups. It resets the computer to the factory default values for the engine (fuel/air ratio) and other characteristics. if you google it you will find out how to do it. Very easy. It'll run rough at first but it learns the way your engine runs. It stops this learning after 50 warm up cycles. Your supposed to drive it normally during these cycles (don't start it up, then rev it to 6000rpms to hear how it sounds) if you don't, you will just confuse the computer and it will learn from that.

pdowty68

Just disconnect the battery and then go inside and "use some electricity" (step on the brake pedal for a few seconds, turn the headlight switch on...etc) this drains the computer of all electricity and effectively erases its memory.

Yfz450

Ok I just read how to reset it. If I do this and the problem continues is the computer to just run crappy like it is

Yfz450

Ok I just went out and reset it. Then took it for a drive. When I started it it ran rough for a few seconds then smoothed out. Then went down the road and it did the missing a little bit but not a's bad a's it normally does. Then I came to a stop and it stalled. Started it back u and ran fine driving and stopping for another 5 miles until I got home. So hopefully this helped I will post again

pdowty68

All the times I've done it , it ran rough for the first 5 or 6 starts. Not full warm ups, but starting it, running it for 30 seconds, then shutting it off. Do that 5 or so times. If it didn't do anything, it should be the same as it was before you did it. Otherwise, it will keep improving for the first 50 starts. So in other words, you will know if it worked within minutes. Let me know!

pdowty68

I'm happy to hear it worked for you!! Like I said, start it, let it run for about 30 seconds (or until rpms are normal) and repeat it 5-6 times

pdowty68

That's why I don't drive it for the first few starts until the engine "learns how to run again" then take it for a drive. Sometimes it will stall out on the first start, sometimes it wont. don't trust it, let it sit in your driveway until you get it all sorted out. Don't drive with a freshly reset ecu. That's not safe

pdowty68

Let me know! I want to know how it turned out!

belvedere

You might start by testing the fuel pressure.