BeardedOneder

Ok so here is the deal, I bought an 89 XJ about 2 weeks ago now. Runs great, but it is 25 years old and has 258k miles on it. I knew there were a few problems with it when I picked it up, but have a question or two for you all. I bought it in another county that didn't require it to be tested for emissions. Uh oh. It failed the "pressure test". They said it has a slow leak somewhere in the system. Does that refer to FUEL system or EMISSIONS system? It doesn't seem to say anywhere on my paperwork. I noticed that when I turn the cruise control on it will slowly slow down then adjust quickly back up like it isn't holding vacuum well enough to hold speed. Seems to me wherever that possible vacuum leak is could be causing it? Where is the cruise module at on an 89 Renix? I did put in new motor mounts, and broke a vacuum line or two in the process, but then promptly bought a whole new vacuum harness as the line going to the top of the crankcase was shot and leaking oil all over the valve cover anyway. It also BARELY failed the nitrogen oxide. Acceptable is 4.50 and I came in at 4.52. HA HA! What's the best way to test the EGR valve? I went ahead and ordered a new one for 30 bucks anyway though that should show up tomorrow. Thanks in advance for the info all!

JBimmolate

Here in My area they Test the Gas cap to make sure it holds pressure and now they also check the evap system to make sure it holds pressure as well.

Miles

BeardedOneder

Right. The gas cap itself passed. I am fairly sure that it is the evap system that failed a pressure test.

DFlintstone

I'd bet on the evap system. There is a line from the tank to that canister on the firewall by the bottle. (leave that bottle 1/2 empty Btw.). I might visually inspect the lines off the tank. Maybe someone can post where that evap line connects. Likewise the lines on the canister, and the can it's self.

You have a large vacuum line off the manifold, back to the firewall, across, then forward all the way to the "vacuum ball", a vacuum reservoir located behind/right of the front bumper. Then there is a small tube that comes back from it to work the cruse and heater controls. (there is a "Y" off the large line for the "disco", 4WD controls.) It's sort of near the evap can.

The link in my signature has a link to Cruiser's tips, also some diagrams. You may want to take a look.

BeardedOneder

Wow! That's EXACTLY what I needed. Thanks for the info and the link. Even more great info in that post. I'll be checking over all the lines when I get home tonight. Now, I'm not looking at it right this second so I might be not thinking completely, but what bottle are you referring to that I should leave half empty?

DFlintstone

The "coolant expansion" bottle. Renix has a "closed" system. Most have a cap on the rad with a valve deal that lets excessive pressure go to a coolant recovery reservoir, then when the system cools coolant is drawn back in. Ours is different. It just holds it in, and blows up sometimes. Leaving air in there to compress helps to prevent that.

Now tell us about your plugs. Champion copper's gapped to .035 is ****. A guy failed last week, probably because he had those goofy platinum plugs. These and them do not get along at all.

I'm a little rusty on the EGR valve. I believe you should be able to reach down and push in on it, then hear the engine sputter.

With a Renix you pretty much need a digital meter. It's ECU stores no codes, it has no nag light. Cruisers sensor ground test is a must. You could just go ahead and clean the business at your dipstick mount. That's your ECU, TCU, and injector grounds.

BeardedOneder

Ahhh the coolant bottle. Gotcha. Yeah it is half full.
I just put in new plugs, wires, cap, rotor when I bought it... but you think I remember what plugs? Haha. I wanna say some cheap Bosch coppers. Definitely capped to .035 though.
Cool. I'll push the diaphragm on that EGR tonight and see what she does.
And I will look into the sensor ground test too! This is all awesome info! Lovin it!

DFlintstone

I'm glad to pass it along, and hey, what better way to learn to type? (I'll never learn to spell). A couple things on high NOx. (besides the EGR system).

These things are prone to vacuum leaks. If it were a tad lean from a leak that might be an issue. Also carbon buildup in the combustion cylinders can cause higher compression resulting in more NOx. Check this water treatment out>
Then here is something on vacuum leaks:

Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep. ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test, see if the engine sounds different.

Radi

There's that guy with the garden hose again!
I wish he'd put that thing away and use something easier to control like a soda bottle or dixie cup.

cruiser54

Welcome fellow Arizonan.

Coupla things.

The vacuum system which controls things like cruise, dash vents etc has a reservoir up under and behind the passenger side front bumper. Hoses run from the intake manifold TO it, and FROM it to the firewall just below the coolant bottle. Known for cracking. Most of us relocate the vac res to up under the coolant bottle.

cruiser54

Now, have you replaced the plugs, wires, cap and rotor yet? Cleaned the throttle body? Oxygen sensor?
Intake manifold bolts not loosened up?

Do #1,3,4, and 5 in my link below as well.

DFlintstone

Yea, I thought he looked a bit "thorough". (and he mentions a couple of minutes). I suppose whatever steam can do, he's doen it!

Pete, do you know where the tank vent attaches to the tank? His HC is OK, pretty rare for an 02 sensor to fail lean I gather.

BeardedOneder

What... I'm new here, but... PLEASE tell me that's a joke right? HA HA! Good lord.
I did do plugs, wires, cap, and rotor. Also, new motor mounts because this was the better of the two mounts...

Did new sway bar bushings since there was only one and it was in terrible shape. Reasealed the rear diff, replaced coolant temp sensor, and oil pressure sensor. I don't think there is an issue with the O2 sensor. Haven't cleaned the throttle body (remove to clean, yes?) or checked the manifold bolts, but will do that hopefully tonight if my wife doesn't have other plans for me. HA! As far as relocating the vacuum res what is the best way to go about getting to it? I haven't tried too hard to get at it yet, but took a quick look last night and that thing sure is tucked up inside there!

cruiser54

Not a joke. Works great when done properly.

Res is easy. Two 10mm headed bolts.

Do the tips as the sensors can send very poor signals to the ECU if they're no grounded properly.

BeardedOneder

Really?!?! Running water through the air intake is a good idea? Sorry to doubt, it just didn't seem like a real thing. Still not sure that's something I want to do as it just feels like asking to hydrolock/bend a rod. Wouldn't a can of seafoam do a similar job? You seem to know what you're talking about so please don't take offense. HA!