Lol I know right

 

Don't you have OBDI?

 

Yeah I do, but I was thinking I could hook up a scanner because there's a port on the harness beside the PCM. I searched online for a while last night and I can't seem to find anything compatible that's reasonably priced. I think most of the high end OBDII scanners are compatible with OBDI with the right adapter, but they're about $250+.

 

Also, I tried resetting the PCM and cranking up the Jeep after letting it sit all night (cold). I still have the issue immediately after cranking. So wouldn't that eliminate fuel trim settings and the O2 sensor? Also, yes my O2 sensor is brand new.

 

Does this look like it'll fit?

 

Yeah, I'd move those down on the list. Besides, I don't know if you could get fuel trim data from a low- to mid-priced OBDI unit. This one looks at these things called Adapt Fuel #1 and Adapt Factor#1, which sound like the precursors to fuel trims.

Despite not finding anything with smoke test, it does sound like it could be a vacuum leak. Running that bad it's definitely sucking in air (if it is, in fact, a leak) so why not try the propane trick?

 

Adapt Fuel #1 (mS)
The additive adaptive fuel is the on-time base pulse width adjustment that is calibrated at idle conditions. For engine packages with multiple banks, #1 represents bank 1 injectors. Displayed in milliseconds.

Adapt Factor #1 (%)
The Adaptive Factor is the long term adjustment percentage to the base pulse width at each adaptive cell. For engine packages with multiple banks, #1 represents bank 1 injectors.

 

Okay, so I did some more tests tonight. I was looking through my tools and I actually do have a gauge that will measure vacuum. At idle its pulling steady right between 14 and 15"Hg. At 1k rpm its steady at 16-17"Hg. I also checked it at 2k rpm and it's bouncing a little more between 17 and 19.5" Hg. I also did a throttle snap and release. Both of those seemed normal. I saved videos of all of these in my google drive folder if you want to see. I guess my biggest concern would be the inconsistency I can see at 2k rpm. This is my first time doing a vacuum test like this so I'm not exactly sure what to look for.

Next I pulled the valve cover off. All of the pushrods are spitting out plenty of oil and the rockers seem to be functioning properly to me. I also took a video of this and put it in the drive.

Next I tried the cylinder balance test but using the dashboard tach I couldn't see a difference in rpm from normal idle (reference) and any of the cylinders having their injector unplugged. I also took pictures of this and posted it in the drive but like I said I think this is kind of inconclusive. I'll have to find a more accurate way to measure rpm.

https://drive.google.com/drive/folde...nf?usp=sharing

Before I got the smoke tester I did try checking for vacuum leaks using carb cleaner but I couldn't find anything. Maybe I'll try the smoke test one more time to be sure.

 

Yes, that looks like it.

 

Wanna borrow it? You pay postage both ways (should be about 16 bucks total) and give me a massive security deposit. The unit is AutoXray EZLink. Here's a manual for their 6000 (looks very similar)

https://www.manualslib.com/manual/88...?page=4#manual

but I have the real manual in hard copy and may be able to find the pdf.

Looks like it can also measure injector pulse width (but we can do that with the Hantek!) and a pile of other stuff although I haven't had an OBD I for about 20 years so I don't know what data it can actually get.

But beats dropping 250 for a scanner you might actually use only once.

 

https://www.allstates.com/propak_instructions.htm

 

I appreciate the offer. Hopefully I won't need to do that. I've got a few more things in mind to check. Tonight I'm going to try the smoke test one more time for vacuum leaks and I'm also going to check the harmonic balancer. That's something I thought of today that I haven't checked.

 

SOLVED!!! Finally I figured it out! After testing everything I could possibly think of it was the two main bolts on the sides of the transmission that mount to the engine block. They were totally loose. I could screw them out with my fingers. Torqued them back down with some loctite and now the Jeep is running smooth as butter at any rpm. It was either throwing off the cps at 1k rpm or causing the engine/trans to resonate at that rpm. It's interesting because my cps reading with the scope at idle looked really good.

I really appreciate the help guys. I learned a ton of new stuff with all the great info!

 

Terrific!

Thanks for the follow-up! That info will absolutely help others in the future!

 

Engine to transmission bolts you say, eh? Verrrry IN teresting. (runs out to check mine)