Hello ladies and gents. I am at an impasse and hope that some of you gurus could help a guy out before my hair turns completely white (I'm in my early 40's). I am completely stumped on this, but it has to be a fairly common issue/fix in my mind. At least that's what I thought earlier this week. Please read on...

First off, I will preface this by stating that this is my base model cheap-Jeep, secondary runabout. It does see some daily driver duties from time to time. It's got about 160k on the clock. Up until now, albeit a few quirks, it has been a decent runner that hasn't given me too many problems. It is all stock, and I only fix things on it when they need attention. Some things have been a bit neglected as long as they were "good enough". The exhaust is one of these things, which I have know for awhile has been in very poor condition, and in need of replacement. The manifold has had the typical crack and exhaust leak for quite some time. Motor mounts are shot too. Other things and other vehicles take precedence, ya know? Now to the problems...

How it all started:
One beautiful Sunday a few weeks ago we were on our way to a local river for some family fun time. It was about a 20 minute cruise down the hwy running speeds up to 70 before exiting the hwy onto a gravel road down to the river. Everything was running normal, albeit a bit loud, due to a rotted muffler. After bouncing a half-mile down the quasi-rough gravel road (average for gravel roads around these parts) the XJ acted like something broke and immediately lost all power, started running rough and stalled. It also got louder, as if the muffler had finally blown all the way out. I was able to re-fire it, but it idled rough and wanted to stall unless I kept my foot on the pedal feeding it fuel. Upon making it to the parking lot at the river and popping the hood, I found the vacuum elbow at the front of the fuel rail was totally disintegrated. Thinking this was my obvious culprit, I replaced it with one off a heater control to no avail. Long story shortened, we managed to limp it home, stalling at lights, running very rough and poorly, with no power all the way home (after some time *trying* to unwind at the water). The next day I finally called the muffler shop and made an appt.

What is new:
The shop I took it to crawled around on it and couldn't find anything. They didn't have an OBD1 scanner and neither do I for that matter. They went ahead and put a new muffler and catalytic convertor on it (nice and shiny to the tune of $660 ). I drove it home, stalling at lights, running very rough, and underpowered. A new 02 was on the way from Rock Auto, which I put in on Monday. I also replaced every piece of suspect vacuum line and elbows. No change. It has had a recent tune up, with new plugs, wires, cap and rotor and an oil change about 2 months before all of this started. Last year it got a new water pump and radiator. While working on it at the river when this all started, I noticed the oil pressure sender (below the distributor on the block) was broke, so that was replaced. I have also replaced the Coolant Temp Sensor at the water pump this week.

What I've checked/tested:
As this week has progressed I've attempted to do my due diligence and have gone through checking and testing everything I have read about that causes these issues. I smeared some JB Weld Extreme Heat over the cracks in the exhaust manifold, though this was after putting the new O2 in. I figured it wouldn't foul a new sensor immediately; my logic being that I ran with the whole exhaust totally wasted for so long and it did fine. I've cleaned the throttle body and IAC. I've used a multimeter to check the TPS and the IAT sensor. The MAP sensor was swapped with two different units I have, one coming from my running '92 305 Camaro (same GM MAP on both vehicles), with no change. The oil is fine, clean, still new looking, with no milkshake. Coolant is fine. The coil has hot spark, all the wires look good, but the middle 4 plugs are fouled with fuel. I assume this is from me putting my foot to the floor trying to start it and keep it running. I opened the box for the ECU, and though I didn't cut any gel out, I wiggled everything sticking up through the gel with the engine running. No change. The fuel rail burps gas if I push on the valve after shutting it off.

HELP!
So, to recap, it'll start right up when cold but idles rough for about 30 seconds and then it stalls. When I try to restart it, it will only crank unless I put my foot to the floor while cranking, then it will fire, chug, shutter, and run like ****, and then stall out again. If you keep your foot in it, it will run, albeit way under-powered, and blowing fuel out the tailpipe. Then you let off and it dies. I'm baffled. I don't want to start throwing parts at it (I already learned that lesson on the Camaro a few years ago, and have since learned how to use a multimeter). Certainly someone has dealt with this, can you point a guy in the right direction, or any direction for that matter? The Missouri Mug (humidity) has set in for the season and I'm getting hot! This 'Jeep Thing' is getting old.

 

UPDATE:
After more hours of research and the process of elimination, I put a Distributor Pickup Coil (Cam Position Sensor) it it today. The old one did have a wear spot in the insulation with bare wire showing through in one spot. This resolved the stalling and the hard starting, but the idle is still rough, fluctuating between probably 500 and 900-1000 RPM, per my ear meter. (This thing is totally stripped down with a big fuel gauge where a tach would be on most vehicles.) So it starts fine and idles, cold or hot, albeit rough. I took it for a ride down to the end of the road and back, and on flat ground with partial throttle, it cruised right along. The return trip, though, was up hill for the first half, and under load it seems to misfire, buck, and have no real power. It never stalled, just had no oomph.

After multiple code resets from checking other things (I finally researched the key cycling trick) I keep getting a Code 13, MAP unchanged. The vacuum line from the manifold to the MAP is fine, and in trying 3 different MAP sensors, nothing changed. If I pull the vacuum line it idles up, but still rough. Again, all vacuum lines have been checked and fixed if found suspect.

I am wondering if this could be a fuel pressure regulator going out? Thinking back to the first day I started having problems, the vacuum elbow on the FPR was totally disintegrated. Could I be on the right track?

 

And now, for the rest of the story.

Well, after more research, overly-methodical fuel injector inspection, and a new fuel pressure regulator, I pulled the valve cover. Broken valve spring on #1 intake valve. Explains the ticking I had been hearing...which I was initially hoping was the crack in the exhaust manifold. Nope. Then, as all optimism was beginning to slip away; maybe? a sticky lifter. Yeah, nope. More hours cruising 12 year old posts (due to my limited but burgeoning knowledge) pointed me yonder and I had to swallow my pride and pull that greasy, neglected valve cover. Once I did it was all but smacking me in the face. Visually evident.

Fixing the broken spring was extremely easy. YouTube can walk you thru it and the spring compressor I used came from Amazon for not much more than $15. RA had a pack of 4 Mellings springs for $12. Now I have backup.

So now it runs and drives like a [brand new] {reliable} dented-up old Jeep! All of this thanks to: a brand new exhaust! (cat, muffler, JB Welded exhaust manifold, and 02 for good measure) A new cam sensor! (which I do believe was also bad due to a raw wire) Various vacuum hoses and elbows along with a new valve cover gasket! The valve spring of course! And last but not least, and because they were $5 each on RA, some motor mounts!

I may just keep it after all..