lawsoncl

That suggests bad battery cables or battery connections. I'd also undo and clean the major ground connections by the dipstick.

Very Red XJ

Thanks, and indeed I'd suggest that you re-tighten those bolts in any case. Chrysler's wiring casement tens to crumble with age letting wires dangle. A short is quite possible - but you'll need good weather or a warm garage to find it

pineapple_tree

Well, considering that the wind chill alone is going to feel like in the single digits, i’m not too interested right now. But i’ll find some bolts to fit the threads for the bell housing, tighten those up, and look for the short after that. Because clearly I have something else going on as well

Very Red XJ

Indeed - stay warm. And don't forget open circuits like the ground for the battery - Good luck

pineapple_tree

Okay. So I got the transmission completely tight to the engine, and it seems that my sputtering problem is partly fixed. My tach is now dead on, and my gear shifts are smoother since I was missing 4 bolts. Shame on me for forgetting to tighten them.

Anyway, i’m noticing a trend for the sputtering. It wants to happen when the engine is between 100 and 210 degrees, right around a quarter of the way to operating temp. This makes me think that either the ECT sensor on the thermostat housing is telling the computer something else than what the intake air temp sensor is reporting, and thus making the computer freak out and not set ignition timing and fuel timing correctly. I’m thinking about just replacing both to be sure of it, but even though I tested the sensors and they showed the right resistance to the temperature they were at, that doesn’t mean that at some point the sensors aren’t reading right.

Will update with more info soon.

And while i’m at it, is it true that re-locating the IAT sensor to the air box improves the responsiveness of the engine? I imagine so because the intake sits right above the exhaust, so it’s not really reading the actual air temperature

psf4x4

What’s the point of testing something just to negate the results?

why don’t you test the resistance at the temp range you suspect something is wrong.

trust the test and loose the “I’d feel more comfortable just replacing” mentality. (Not your quote but I feel appropriate)

or replace, test again, replace, test again and then wonder why the problem isn’t solved.

doublechaz

Since it improved when you moved the transmission from where ever it was to where it belongs tight against the back of the engine, I would look at the crank position sensor. There is some amount of physical alignment adjustment, and there is also cleaning all the crud from the sensor and teeth that are probably there from running it with the trans dismounted. At this point the other sensors that tested out good should be at the very last position on your list of things to do.

lawsoncl

If the resistance measured good, the sensor is probably fine. Look over the wiring to it and make sure the wire isn't damaged near the sensor. How old is the O2 sensor? I'm wondering if that's bad or the power to the heater part of it is bad, that might make is slow to warm up before the ECM tries to switch to closed loop mode. Although it should be cutting to open loop mode when floored.

pineapple_tree

Well, here’s what I can do. I can measure the resistance of both temp sensors and find a way to heat it evenly, and see if the resistance steadily rises, to make sure there isn’t any dead spots. I’ll try to measure the resistance of both at about 140-160, which is where it seems to sputter.

I also don’t have a problem with replacing both, because as far as I know, not a lot of care went into this Jeep. There’s no records of anything being done, so I just have to go off what I see, and when I see the ignition coil connector wires taped together because they’ve been cut, then I start to assume the person who last had this jeep was brain dead

Very Red XJ

Glad that you tightened the bellhousing to the engine and saw an improvement! Often there is more than one problem, and apparently your jeep has fallen into that category. All of your sensers affect your PMI in dictating timing, and air/fuel mixture at a measured temp and throttle position. Any one of them could through off the mapping at the wide range between 100 to 210 degrees. For me it was a dangling wire from O2 sensor along with the fuse it blew, and dirty injectors. Testing will tell you where to spend your money wisely

The pins are for the wires

Testing restance in cleaned injectors

lawsoncl

The temp sensors just don't fail that way. They're usually broken and not reading at all, or way off across the board.

pineapple_tree

The injectors are next on my list. I’m nearly 100% sure they are the factory installed ones, and I’ll test them sooner or later.

I’ve also looked for codes stored and nothing is being stored, so that makes me think that whatever’s causing it, isn’t something that’s “monitored” by the PCM.

I should also note that my PCM had been replaced at some point, and it has a sticker on it that’s your typical “void warranty if removed”

And to the other guy about how the temp sensors work, that’s a good thing to know. I thought they scaled kind of like the TPS sensor, but it’s good to know that they usually fail all together or give some absurd reading

Very Red XJ

I dug a lot of muck out of my injectors, sprayed carb cleaner through them using a 9-volt battery and a pair of wires with alligator clips on each end that I bought at O'Reilly's. You should hear a "click" when you connect
Unfortunately, The PCM can only measure resistance and note a short or open circuit. A flat spot in the TPS, for example, is beyond the PCM's capability, but easily viewed on a VOM

pineapple_tree

I did some driving today to figure out exactly what causes it, and so far i’ve found that it will never do it when I first start it, and it’ll only sputter and buck between about 120f and 180f. Once it reaches 195 and the thermostat opens, it doesn’t do it until the next thermostat cycle.

Ive also found out that when it does happen, it happens right around 1.5k, and will continue until you let off the gas. If you don’t, it will continue to sputter and buck until it hits 3k, then it stops all the way. You also have to be laying on the throttle, and it only happens in 1st and 2nd. When I shift to third and lay on it, nothing else happens.

The best way I can describe this issue is that it feels like i’m tapping the throttle very rapidly, except i’m not.

While I was at work today, I also stumbled upon an article that was talking about distributor sync. Basically, the issue in the article was “random misfire under load”, and it described re-syncing the rotor to the proper position. It said to set cylinder one to TDC, open up the cap, and the rotor should be coming off of the first contact point. If it’s not, then adjust it to the proper position and test driving.

Now, this might be something worth looking at. I would describe this sputter as a misfire, and considering i’m narrowing it down to either fuel or spark, then it’s worth looking at.

I want to do some more testing, but considering it’s snowing and it’s really cold outside and I don’t have a garage, it’s hard to find time outside of work to start testing more things. I could clock out and use a bay, but it’s so slammed that I don’t have time, and by the time i’m off work, it’s dark and cold. And then when it’s the weekend, it’s snowing and even colder.

So, bear with me on this. I’ll figure this out eventually, but it’s still running and driving. For now

exasemech

I hate to bring this up for fear of setting things off in another direction but you started another thread about what you describe as a possible valve train "rattle". Ya know, if you have a collapsed lifter .........
You might want to pull the valve cover and try to figure out what if anything is going on with the valve train...could explain a lot....maybe