Renix Pinging, Cold start rumble, and over-all emissions maintenance

So for a while my 90xj has been giving me a ping right around 1750RPM and then again at 3500 RPM. It only does it when under certain loading conditions (usually going up a hill). Typically when it does this, I'll either back off on the throttle (it goes away) or I'll hit the throttle enough for it to down-shift at which point again it goes away.

I havn't really done a lot of debugging on this issue, mostly a lot of searching (most people seem to have more persistent issues than mine).

I am not specifically sure when the issue first cropped up, but I seem to think it started around the time I replaced the radiator. (this was a whole 'nother fiasco) but ever since it's been running cool ~185, I typically run a factory 195F T-stat in it, and with the previous radiator, it sat at a perpetual 200 unless I was really pushing it around.

The other annoying habit it's been giving me lately is with what sounds like a stuck lifter on cold startup. It doesn't do it every time, but some times it will sit there and give me a loud tick/rumble, if I gas it it goes away until some cold start again in the distant future. This could be the flex-plate bolt issue I've read about, but I'm not sure. Oil pressure starts low for about 2-3 seconds and then immediately comes up to about 60PSI (running 5W40).

I'm getting ready for my final smog inspection before it falls off (25 years!) so I kinda wanna start debugging things now, while the weather is still nice.

Also, what's the expected lifespan of an O2 sensor?

Other than the noise, and the ping (which kinda hurts performance going up hills with the loss in power) it still runs great and gets over 21mpg highway...

Have you tried a higher grade of gasoline?

Have you used ATF engine clean-out for 10 minutes of run time?

Have you tried STP?

Gotta be mechanical if ATF, and then STP with fresh oil change does not fix it.

A tick, and rattle sounds like the lifters are not holding a charge. Hit 70 in a 258, at 43k miles, and that happened, and STP helped, (almost sounded like a spun rod bearing about to throw the rod, or a wollared out wrist pin hole in the piston), but I after inspections went ahead and changed out old lifters with new ones, and no problems for the next 210k miles. Never heard the sound of a "rumble" associated with a lifter issue though. New one to me.

You over around tanasket, (sp) ?

Check out this link: http://www.naxja.org/forum/showthread.php?t=61187&page=2 and see about the 14 point diagnostics using a vacuum gauge tool for your issue(s). Great info.

Alaskan brings up a good point a vacuum leak may be causing a lean burn ping at certain RPM's. It could just be on a cylinder or two.

The knock sensor is supposed to retard the ignition when ping happens, maybe yours is toast or the wiring is cooking on the front of the exhaust manifold.

I've seen a lot of XJ's where the front harness gets routed wrong after a power steering pump removal and remount. There is a blind spot behind the bracket that makes it almost impossible to see the spot where the harness often cooks on the exhaust manifold.

EcoMike says you can unplug the O2 sensor and make a test drive and see if anything changes. Anything that causes a lean burn condition may cause pinging, anything from the O2 sensor, to a fuel delivery issue. The 1750 RPM and 3500 RPM makes me suspect an O2 sensor. Mainly because I've had the Renix buck at these RPM's (not exactly but close) before from an O2 sensor issue. Bucking and ping can both come from a lean burn condition.

Jump the ballast resistor.

I'be never really had any pinging issues with my Renix, but I have had bucking issues. Twice an O2 sensor, once a TPS with a dead spot. Maybe they were pinging and I never noticed, bucking is hard to ignore.

Alaskan,

I typically do a seafoam treatment before every oil change, and change religiously at about 5K, I also change oil seasonally, running 5W-40 in the summer, and 0W30 in winter. The lifter charge may be an issue, I'll look into that and maybe pop the valve cover (which I havn't done in a number of years at this point anyways, so I'm overdue).

Also, any opinion on marvel mystery oil? Ecomike recommends it, and I use it quite frequently, it's cleaned up more than a few cranky small engines, and seems to do good for the jeep.

The lean burn is a possibility, now that I think about it, I did install a new fuel pump about the same time, perhaps under load it's not pulling it's weight, or there is an electrical condition keeping the FP from getting full power. Checking the electrical conductivity to the FP is a lot easier than driving at 60mph uphill with the hood open running along-side watching a fuel pressure gauge.

The O2 sensor is another culprit I suspect, I think it's been in there for 4-5 years at this point, I think I have a spare, might swap it.

8mud,

As far as the knock sensor goes, I did check that, and it seems to be in there with good wiring (yea I know, a renix that actually has good wiring *shocked*).

Given the varied conditions I've been driving in lately (hot humid, cold wet, hot dry) I should probably go through the battery harness to make sure I'm not having low voltage conditions contributing to my problems.

I'll check the knock sensor again, perhaps do the strobe test some people have mentioned (hook up a timing light, and then tap on the engine near the sensor and look for it retarding). I did put a new harmonic balancer on it recently as the other one was wobbling and making noise and it seemed like it was time for that to go.

Both,

Any ideas on flexplate issues? I did some more reading after posting, and that usually seems to be more an issue when the vehicle is under power. Either way, I'm going to hit the bottom end with the pressure washer and pop the inspection cover and look for loose bolts.

It's probably time to put in some fresh motor and trans mounts as well.

I use MMO with every oil change. Also keep a spare quart in all my vehicles, as it can be used in addition to almost any fluids. Disco the OXY and knock sensor and see if anything changes. Renix will run without these, using default ECU info.
When I first had my current XJ, it had a lifter tick. Would go away a good tap on the throttle, came back a couple times. Then went away. My friend Chris uses a method that works well also. With engine up to temp, of course; Rev/hold @ 2500 RPM for 30s, then 3000 for 30s, etc all the way to 4500.

Reading another post reminded me, the wrong plug can increase pinging. Most times you are better off with the standard plug unless you are doing deliveries or short trips. A lot of low vacuum high speed driving and you often need one plug colder. Champion RC 12LYC is the recommended plug, which was discontinued for awhile, but seems to have been brought back again. The lower the number the colder the plug for Champion. The recommended plug (from Jeep) for the autobahns (a lot of WOT driving) was RC 9YC.

I've never had any pinging issues in any of my Renix, no matter what kind of fuel I used (even Albanian ).

So I pulled the O2 Sensor connector (disconnected) and the pinging is still there... so probably a bad O2 sensor at the last. I'm not sure what plugs I currently have in it, IIRC I usually run the stock autolite plug. I don't tend to do very many short trips on a regular basis, I know sometimes I'll do a bit of running around, but usually that's 1-2 days a week. Most often, I drive for at least 20 miles at a time, and frequently I may be driving hundreds of miles at a time. So perhaps the cooler plug would be a bonus.

I'm still taking my time picking through the vacuum system, I know a while ago I cracked one of the nubs on the vacuum bottle, but I glued it back on with super-glue and it seemed to stick. It looks like a replacement is $8 at 4-wheel-farts. Might just relocate the whole thing after the ABS delete anyways.

Also, any thoughts on replacement transmission mounts? I'm currently debating browndog vs/stock motormounts... I would like to do the BD's but that's really not in my budget, wondering if I should just suck it up and save myself the trouble of having to do them twice.

Ok, so got around to doing a bunch of maintenance and wanted to post a follow up...

So new motormounts installed, did some clean up and pro-active hose replacement.

That said, I've been running 1qt of MMO in the engine on and off since i've owned it, added more today. Anyways on a "cold start" the tapping was there. and it seems to be coming from the #3 cylinder. It will start tapping, then go away and then build up over about 10-15 seconds to a loud tap and then stop for a minute.

In my previous debugging session I sat around and played with the EFI rail, and noticed most of my connectors on the injector wiring harness could be best described as "well used" Replacement seems to be a likely outcome of that process (anyone know where I can get the wires?)

A few people noted the pinging was a "lean ping", while that makes sense I'm wondering why it's getting lean, as I said in my previous post, O2 sensor seems to be toast. I have a spare I'm going to put in tomorrow so I can take it out and do some driving. I know when the engine is cold it does hunt for a running RPM going from about 200-1000 RPM. I did pull off the valve cover and didn't notice anything unusual, I gave the rockers the usual palpation inspected the seals and everything seemed to be in good shape.

Also going to stop by 4WF tomorrow and see if I can get that vacuum bottle and some new sway bar bushings (so that's what that clunk was?)

I hate that sway bar clunk, mine was in the habit of loosening just enough after off-roading that it was a regular issue. I replaced the stock torx bolts with some brand new m10.9 hex from True Value, so now I can just use two 19mm wrenches to tighten. It hasn't loosened up again since, though.

Ok, so after almost 2 months I found the problem....

I put it in 4-full time (NP242 transfer case) to get through some unpleasant road conditions, and noticed a lot of vibration and whirring noise. A familiar vibration and whirring noise, the kind of vibration and whirring noise that comes from a set of bad u-joints.

So I pulled the front driveline, and I don't know what is/was bad on it, but it was pretty crusty, crusty enough that I thought I should spend the time and effort to rebuild it. (I'm going to put together a write-up on this, took a few pics of my tribulations) In the mean time I was using this one as a reference: http://www.stu-offroad.com/axle/driveshaft/driveshaft-5.htm

Anyways, unlike the newer heeps the Renix takes a 5/16" wrench, not an 8mm. Not sure what the thread specifications are, but the head is definitely 5/16 (I almost stripped one of the heads off trying to break it loose)

So the drive-line is in process of rebuilding over at my shop, and I drove it home tonight, cause I was just too damn tired to finish. And guess what? Not only was there no noise in 4-PT (I wanted to make sure the noise wasn't coming from my transfer case) and not only was that not an issue, but that pinging was gone!

Now, I ordered the replacement spicer CV ball-boot thing (still ~$65 from napa ouch!) it's showing up in the morning. I got a full set of duralast gold greasable joints (3).

So I have two questions:

First - On disassembly, I didn't find and smashed or peanut-butter bearings, and the shaft over-all felt to be solid (no clunking) or other obvious wear problems. However the nose of the shaft (that goes into the CV-ball thinger) was kinda rounded, and looked like it had been turned down. The grease that was remaining was dry and about ready to turn into powder. I'm kinda wondering if any damage to that nose part may have worn. Here's a photo:

I don't know what the diameter is supposed to be. Anyone help me out on this?

Second - If this is damaged, what are my options on pulling another one from the pick'n'pull? I.E. what years interchange?

Again, all help is appreciated. I wanted to update this thread with all the pertainent info-mation so it can help someone else.

Other update: as far as the swaybar clunk, one of my swaybar bushings (driver's side) was all rotted out, put a new one in. Problem went away.