mlang88

Hi Guys
My daughters 2000 sport is experiencing Random rough starts usually after its warm. Its definitely missing but the weird thing is if she turns it off and starts it right back up again it runs fine. I had her come by and I pulled the codes and got p0300,p0301,p0303 and p0304 so a random and 1,3,and 4. before I gave her the jeep I basically went through it. the guy I bought it from put a rebuilt engine in it. the only thing I Haven't touched was the cam sensor and crank sensor. my question is has anyone ever heard of the CPS randomly acting up I thought one they go bad that's it. also do you think it could be a ECM issue

Thanks
Matt

BlueRidgeMark

Welcome!

The CPS will normally give a no-start or a shut down rather than random misses. Not sure if the cam sensor will give random misses. The CPS can definitely be a random thing. You'll get either no-starts or shut-downs, though, and it starts to happen more and more often. Then one day, it's all over. OR, it will go completely out in one day. I've had both happen.

The 2000s are known to suffer with some heat soak problems with the injectors. I don't know a lot about it as I've never had a 2000, but do a search here and you'll find tons of info.

mlang88

Thanks for the reply
the weird thing it can happen even after a short drive from a cold start I was thinking maybe sticking injectors? doesn't heat soak usually take a while to cool down before it starts again? this thing will start right up again and run perfect if you shut it down and start it back up

Roler

Both my CPS and CAM sensors caused stalling/backfiring/running rough issues when they started to play up, separately from each other over time rather than the no-starts or shut-downs.
All electrics and sensors can give intermittent issues, making it sometimes challenging to sort out...until it is no longer intermittent but permanent.

You said not having touched the CAM and CPS
Any info from PO having replaced those while rebuilding engine?

mlang88

He didn't say but the cam sensor looks new but IDK

Roler

What's weird is the fact when it's doing that and the engine is shut off and started again right after, it seems to have 'cleared'..

I'm trying to think what would make sense doing that.

Yes, heat soak that we all think of in 00/01's would be different. More the other way around.

CPS and Cam are still on the cards though

BlueRidgeMark

Good to know. I had not heard that.

So, agreed, those guys are still suspect. The other question is, are they Mopar? Or aftermarket?

mlang88, the reason that matters is that aftermarket sensors on these beasties have a horrible reputation. Anything from bad out of the box, to failing in days, to weeks, to months. I've heard ONE person recently say that he had a no-name last him for years. In contrast, this and every Jeep forum has tons of horror stories about them.

mlang88

So she came by last night and I pulled codes just to check no misfire codes but I did get a O2 heater code so maybe an O2 sensor acting up? I was looking around with a flash light and I swear I only seen one bolt holding the CPS on is there at least a locating pin to line up the CPS

318SixPack

Disconnect, clean, and reconnect the Cam Position Sensor harness. Do the same for the Crank Sensor.
See how it runs.

If there really is just one screw in the CPS, then get the second one and secure it too. (I don't remember what size and pitch it is. If you need to find out, take the existing one to a hardware store and match it up. probably schmetric).

Roler

Definitely secure that CPS with 2 bolts. If its out of wack, it could well be its not working as it should, so take that out of the equation.

The code for the sensor, do you know for which sensor it would be?
The upstream sensor is more involved with engine running management than the downstream one, which is basically for the cath monitoring as I have understood.

BlueRidgeMark

The head is 11mm, but I don't know the pitch.

Definitely take care of that first.

Always fix known problems first!

318SixPack

Are you sure it isn't 7/16"? I can't find 11mm hex head bolts in any of the charts that come up in my sloppy searches.
https://mechanicalc.com/reference/fastener-size-tables

BlueRidgeMark

I'm going from memory of the last time I changed one a couple of years ago. So, I'm 100% sure that's what I think I remember, probably.