GanderThePanda

Hey guys, I spent about an hour doing research but I'm not really getting anywhere with my issue.

I bought my xj about a month ago as I plan on fixing her up. There was no issues apart from a small trans leak I noticed when I got home.
It's sat on the driveway since then pretty much.

Last week I took it for a drive around the block just to keep the engine lubed up when the trans started to slip unless I revved it. So I drove it back home and left it on the drive with the intention of changing the fluids when I next got chance.
A few days later I noticed a small wet patch at the front of the jeep so I looked underneath to see that one of the hoses had a small coolant slushcicle forming. ( There was a cold snap around -18c when this happened)
So I finally got around to getting a coolant tester to check it and it read that the freezing point was around -18c) so thats not good...

And so today I topped up the coolant reservoir with some 100% with the intention of letting it run for 15 mins to get to op temperature whilst also topping up the trans fluid.

When I went to start it, it started like normal but it was idling very rough, rpms constantly going to about 1000 and then dropping to as low as 200. Interior lights were flickering when it dropped too. What do you think would be the cause of this? Do you think the coolant froze to a point to cause some damage to something?

Thanks guys!

PatHenry

The lights were flickering? Given the super cold weather (-18C is about 0F according to google, so that's freakin' cold... my toes are frozen around here and we've only hit the teens in F), and the flickering of lights when rough idling, I'd suspect that your battery may be in play... The XJ is pretty picky about having a good battery and cold weather is real hard on batteries.

Certainly there are a number of things that can affect idle, but how I'd start if I were you.
1 - Inspection of wiring and vacuum hoses under the hood. Correct as necessary.
2 - Cleaning and tightening of grounds and battery cables. Clean shiny metal to metal and tightly connected.
3 - Battery test. Load test if possible. Many auto parts stores will do this for you "in-vehicle" for free (assuming you're in the U.S... it's not quite as common outside the U.S. from what I've heard).

If you haven't got a copy of the FSM, head over to cruiser54.com or xjjeeps.com and download one. Lots of awesome info there.

Another possible issue that might be cold temp related idle issues would be if there is water in the gasoline... maybe pick up a bottle of "dry gas" for FI vehicles and a fill-up at a reliable gas station and see if that helps. Maybe shop for this when having the parts guy test your battery.

PatHenry

Could you have like cracked your block or head with freezing coolant... sure, it's possible. It's not common in the Jeep I6 engine from anything I've ever seen. These engines are legendary for their durability and isn't that what they have freeze plugs for?

Do the stuff I mentioned, it'll cost you like $10-20 if you're in the states and have an autozone nearby and 1 and 2 should be done on a new to you Jeep even if it's running well just as standard maintenance.

GanderThePanda

Thanks for the reply guys! Good to hear that it likely isn't a cracked head!

It's around 0-5 c now and it doesn't look like its leaking coolant since it warmed back up.

I have a battery load tester at work, however I'm currently in quarantine thanks to my wife contracting corona working at the hospital.

So I'm kinda limited as to what I can do at the moment.

I have some jumper cables, I'll run those from the wifes car, and see if that removes the battery from the equation.

PatHenry

I really think you'll find it's a relatively minor thing like a bad battery, loose connection, cracked vacuum hose or water/bad gas... the cold is a bi1ch on stuff.. metal expands/contracts, old rubber is hard and brittle, and having it a month means a lot of unknowns...

The 98 head was solid... the head cracking is pretty damn rare outside a 00-01 due to a known manufacturing flaw.

The connections, wiring, grounds is a must do... right up with fluid changes on a newly used vehicle. Take advantage of being home... your Jeep doesn't count as a person, so get up close and personal... lol

GanderThePanda

Cool, I'll try what you mentioned.

I haven't changed the fluids yet as I was planning to drop the tranny and replace a few seals to fix my leaks. But now I'm worried about the coolant freezing.

I'll update tomorrow and see where I get.

I may as well order my manuals too instead of waiting till it warms up.

Thanks again!

GanderThePanda

Ok, I rechecked my battery connections, they were great.
However I didn't have anything to test with.
Whilst I was under the hood I noticed that my cvv hose was all taped up so I thought maybe that would have something to do with my rough idle...

So I started the jeep and shifted from park through all the gears back to neutral (as I wanted to check my trans fluid level) and bam! As soon as I shifted from park into reverse She was running normally again. I wonder if it was stuck between gears yesterday?

Anyways. Now that its running a little happier I'll get around to swapping the coolant as soon as I can before it gets cold again.

Thanks for the help!

BlueRidgeMark

That's a weird one!

Thanks for reporting back!

PatHenry

Yeah, that's great news!

I'm a stick shift guy, so I have no experience with the AW4... it's a damn sturdy auto though. Some folks have trouble with their NSS, which causes "no start" type issues and often cleaning it up is sufficient. I've never heard of a mid-shift point issue with engine function, but it makes sense logically.