After weeks of looking over other threads I'm taking the plunge in hopes to get some smarter brains in on this and hopefully it can hopefully help someone else. It's a 95 with the older ECU, this one is serial number 56028473, which seems to be the hardest one to find of course. The rough idle has gotten worse to the point it's un-driveable. Idles worse when cold and the IAC does the sucking thing to keep from stalling until it can't keep up it seems. Popping out the tail pipe and sometimes at intake. Smells like it's running very rich. Replaced crank sensor, cam sensor, IAC, TPS, MAP, checked plug wire routing and firing order at least a dozen times (new plugs and wires, albiet cheap wires - better ones are coming), have a Hughes plenum repair kit installed and did double check to make sure it's not leaking and don't see any oil in the intake when looking down through the tb, have taken out the 02 sensor in hopes the cat was clogged and made no difference, loosened distributor to move slightly one way or other for fuel sync (I don't have a scanner for this obd1 setup for a live scan to really dial in the sync) and that made no difference, just replaced the intake air temp sensor and throughout all sensor replacing I have reset the ECU. Can hear the fuel pump kick on and it's sitting at about 40psi. There has been one time through all the troubleshooting that it smoothed out and idled pretty well with just the slightest miss every now and then (after warm up), but that was short lived and after next restart went back to same even though I didn't change anything. No idea why it smoothed out other than the ECU finally caught on.

What I'm down to is, can it be the ECU is toast? How would I test that? I bought a $300 scanner that had a obd1 adapter and it told me no codes and that it couldn't live scan this particular vehicle - too old. Can a 95 be live scanned?
Also, I have a slow oil leak that's coming down the passenger side engine mount...I suspect it's from the head gasket, but can't pin point it. Could a leaking head cause all this??
Thanks in advance for any guidance/help!

 

OBDI will hand you live data, if you have a scanner that can talk to it just right.

How much slop in the timing chain? What brand sensors did you install? Plugs? These trucks REALLY dislike the rare-earth plugs.... standard copper plugs are a lot less problematic.

How many miles on the truck? Done a compression or leakdown test?

 

The timing chain and gears are new as well. Have not done a compression test and only did a leak down on the fuel system and it checked out fine.
Sensors are, sad to say, from parts stores (Autozone, Oreilly's depending on what's in stock). I always try to get from dealer to get Mopar if I can, but they never have the part, always discontinued.
Just turned 100k on the truck. I drive it on weekend only as of late and have taken it on the occasional road trip. The last one to New Mexico from Ft Worth. I got some tailpipe popping on that trip. Replaced wires and plugs with some crap I got at the local shop in Ruidoso and solved the popping (I think #7 wire was getting toasted by the header just from being close to it). Drove fine on the way back. But ever since that trip it's been a slow progression into what I'm dealing with now...I was really leaning towards a clogged cat but taking out the one and only 02 sensor doesn't change anything.

 

For the crank sensor, you REALLY need a mopar sensor there. If you can get the dodge part number, you can search on that, and find them on amazon, or ebay, or the like. These trucks just don't like aftermarket sensors in critical locations, and ya don't get any more critical than the crank sensor.

I never had any luck with aftermarket IAC either. Stalling it stops, unstable idle, etc. I put in an OLD IAC I pulled off another motor, reset everything, and most of those problems went away. (the engine did have 200K on it, so, I expected some issues. )

The rest are probably ok though. I have an aftermarket TPS on my current truck, and it seems to do the job ok.

But, it sounds to me like a leakdown test on the engine really is in order. It will not only tell you how bad the leakdown is, it will also tell you where it is going. These engines are famous for cracked heads, around the valve seats.... and if it gets bad enough, well, you get popping out the exhaust/intake...... if it has gotten worse over time, that's another indicator...... But, no point in fixing that if the rings are toast.

Do you have an air compressor available for use?

 

Awesome info! Thanks, man.
I'm searching out a mopar crank sensor (part 56027871) now.
I do have a compressor, guess I just need to get a compression gauge now.

 

You want leakdown gauges. Its two gauges on a manifold. Air goes in one side, out the other side to the cylinder. (cylinder at top dead center, both valves closed.) pressurize the cylinder.... the first gauge tells you what input pressure is. (and is regulated on the good ones, with a ****.) second gauge tells you what pressure the cylinder is holding. Do the math to get percent leakdown. I generally just run input pressure at 100 PSI, so I can just directly read the second gauge for leakdown %. According to theory, anything less than 25% leakdown is 'good'..... and all cylinders should be within about 5%. Some books say 10%..... I prefer to err on the side of caution.

The part I like best is, not only can you see just how much leakdown you have, you can also HEAR where it is going. It's awesome.

You can likely rent one from your local parts store. Probably not a tool you will use enough to justify owning one.

 

You're flying blind there, what scan tool do you have ? Pretty much all modern tools are marginal with pre-OBDII vehicles, finding something 10+ years old would be better.
Running rich, popping, bad idle makes me think O2 sensor or vacuum leak. Did you try to run with the O2 sensors disconnected ? Also disconnect the hoses at the intake (PCV, vacuum etc.) and plug the ports.
Given that things are getting worse while the engine is running I don't think it's a compression problem (yet...).

 

Try this! My pvc valve started to rattle at idle and had low/high idle because of it. Cap the plug on the intake and see if it makes any difference. Being it's 95 it has EGR valve, They have been known to stick open and cause problems.

 

Pretty sure I can rent one. Good call.
Man, I'm afraid of what the results will be of a leakdown test!
I'm willing to bet I'll finally figure out the slow oil leak, though!

I don't have a scan tool. The one I bought that wouldn't do live scan I returned since all it could do was read CEL.
I've taken off the EGR and did my best to clean it out (there was a little carbon build up, but not a ton) and it seems to be clear and working properly.
Going to try and track down a Mopar crank sensor today and rent the leakdown gauge set.
I have replaced the PVC with a factory one and have tried removing it while at idle and plugging the intake hose. It did increase rpm when I did that, and when I put pvc back it decreased rpm.

 

Ok, quick update...

So, before doing much more I went back to basics. I have the crap auto parts store crank sensor in there and since putting it in the thing hasn't run well and I convinced myself it was actually running worse. I also have put in the new cam sensor.
Decided to pull the crank sensor and put the old one back in and leave the cam sensor. Unhooked battery to reset ECU.
Started up and sounded smooth as butter. Just drove around block and seems perfect. Will take on longer test ride in a few.
So now I'm really confused. I know on these older 2nd gen's the cam sensor DOES have an impact on idle and the later ones only impact startup (do I have that right?) and if that's the case maybe it's the new cam sensor that smoothed things out?? I did do some rerouting on the plug wires to clean things up and minimize crossing. Not sure what all helped and not wanting to question it too much! lol
Fingers crossed the longer test drive goes well.
Appreciate all the great info thus far! This forum is a life saver!