My New MJ Lots Of Q's

So I pick up my new 89 MJ today. Its specs are 4.0L AW4 2WD 258K

I have a few questions.
1) once I started up it up the oil pressure was at 60 then after about 5 minutes of driving it it started to go up. Then it was at 80 and stayed at 80 for my entire trip home of 1 hour. Is this normal?

2) It seems to have hard starts. I mean it starts up but it sounds like its really cranking hard to get started. Could it be the starter? And it sounds ALOT different than my 92 XJ when its starting, my 92 is quiet and starts right up.

3) It also seems to be really loud in the cabin, is that becasue MJs didnt have that good of insulation or anything?

4) It seemed to have somwhat of a low idel it never died but it was pretty low in the 600's. Any ideas on that one?

5) I went out for another drive once I got home and went down to the store, and when I put it in park the RPM jumped up to 2000 and stayed there. Any idea on what could cause that?

Thanks
Chris

I will prob have more quesions as I take a look at it tommrow morning.

I have a few questions. - And I'll take them in the order listed...


1) once I started up it up the oil pressure was at 60 then after about 5 minutes of driving it it started to go up. Then it was at 80 and stayed at 80 for my entire trip home of 1 hour. Is this normal?

I know my 88 and 89 tend to wander, but I've not had spikes like that. However, as long as it's spiking up and not down, I'd not file it under "critical." Oil pressure for you is still nominal, so we can look into that later.

2) It seems to have hard starts. I mean it starts up but it sounds like its really cranking hard to get started. Could it be the starter? And it sounds ALOT different than my 92 XJ when its starting, my 92 is quiet and starts right up.

The 89 uses a RENIX engine, with somewhat unusual pre-OBD electronics. The Engine Control Module (ECM) does not "wake up" and send ignition and fuel injection signals until the Crankshaft Position Sensor (CPS) registers 300rpm or better. This is meant to help with oil distribution on startup.

If you are concerned about this, the best fix available is to go to a local starter/alternator rebuilder and tell them you want a starter that generates more torque, as this will get the crankshaft turning quicker. If you don't have a local, I can give you the address of the one I use - his prices are good, and I've always been able to install his parts and forget them (I met him when I was an industrial mechanic several years ago, and that's stuff that gets ABUSED!)

3) It also seems to be really loud in the cabin, is that becasue MJs didnt have that good of insulation or anything?

Check to make sure the exhaust downpipe is solidly connected to the collector. Replacement nuts are threaded 3/8"-16. I used brass nuts with LocTite 272...
I'd also look for any exhaust leaks in the downpipe, and check the flange at the catalytic converter inlet. Those nuts are the same size as those on the collector.

4) It seemed to have somwhat of a low idel it never died but it was pretty low in the 600's. Any ideas on that one?

Check that figure against your emissions label. I want to think that autos idle a little lower than manuals, but it's late and I'm not going outside to check right now...

5) I went out for another drive once I got home and went down to the store, and when I put it in park the RPM jumped up to 2000 and stayed there. Any idea on what could cause that?

I knew once - I'll have to check my notebooks. My 88 does the same thing on rare occasions, and my 87 did it every now and then as well. I'm tempted to think it's a misengagement of the "cold start/fast idle" circuit, but I can't swear to it right now. I usually gave the accelerator a tap once or twice (bump to 2500-3000rpm or so) to clear it. Since it always cleared, I never bothered to fix it (yet...)

Thanks
Chris

Yer welcome. Just remember, if you think you're having too many problems with your new MJ, my wife and I would love to give it a new home (ALWAYS marry a woman that likes Jeeps - she doesn't complain about the three we have and likes the idea of getting both an MJ AND an M35A2 as much as I do!)

5-90

congradulations on the buy
1, change your oil, what kind of oil is in there now, you probably want to switch to a little lighter oil since winter is coming


2, all of my comanches's have started hard, even my 4cyl, look at it this way, the longer you crank the more oil you get going in your engine, that or get a bigger started

3,check all your metal, might wana get underneath of it and see what shape the floorboards are in, and check for exhaust leaks as usual,
on the otherhand, who cares if its loud its a truck!

4, check your egr valve, also, the trottle body will need to be cleaned, and make sure you get the IAC sensor while your at it, also your manifold bolts are also are probably loose, tighten them up, just to 20ftbls, no more no less

5,map sensors usually seem to be the cause of high idling, mine did it all the time, it was terrible
what i woiuld do first is get a voltmeter and test every sinlge sensor
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

the renix is not like the ho's they are a little more touchy, you need to keep an eye on things, and even with plenty of time put into it, its still going to act up from time to time,

what are your plans with this truck?
i saw it was 2wd maybee a tow vehicle?