To start off, I've got a 89 Cherokee Laredo, 4.0. I have noticed some symptoms the past few days. The most simple way to describe it is it feels like the TPS is bad. Shifting feels a bit off, some hesitation, just feels a bit sluggish. I also noticed I went from 13mpg to 11mpg my last tank. I replaced the TPS with a brand new Mopar unit, and adjusted it to spec as always via Cruiser's instructions. It felt okay at first, but then it came again within a few minutes. I noticed the symptoms are not ALWAYS there, sometimes it will feel okay, but then it will feel rough as I coast into a parking space. The hesitation is most noticeable when just barely on the throttle. When cruising around in a parking lot today, the hesitation was more noticeable than ever, and it felt like it was gonna die. It kept going, however I decided to pull over and take a look. Double checked the TPS adjustment. Checked injector connections; a couple of them actually have a bit of play, one of which I could just pull off pretty easily. Right now they are Ford 700 injectors, never liked them. I felt like I went backwards after ditching the stock injectors. I have a set of 746s en route. I figured I would look for a vaccum leak while I was inspecting everything. I found a danging tube, but can't find out where it could go. It attaches to a metal line directly behind the intake/throttle body toward the firewall and heads toward the rear axle. I found it dangling on the passenger side. With the engine running, I can't feel any vaccum on it. There was another metal line, and it is hard to tell but I believe it runs to the vaccum disconnect on the front axle. However, that line stays metal the entire time. The line I found runs from the rear end towards the front, up into the engine bay, attaches to a rubber hose, crosses behind the valve cover, and I found it there. I am not sure if this is related, or not. My vaccum canister appears to be hooked up correctly. I have one of the pill-shaped units, with a bunch of lines coming out, as opposed to the two-line simple style. It stores vaccum and I've got air coming out of the vents, so I assume it's working. On the way home from the parking lot it felt okay, but it just felt like something was holding it back.

 

Just in case, here are some quick pictures of the line I found. Just a normal looking vaccum line, but converts to a metal line.

 

I might be able to help you out some here and there. Of course Cruiser will be a big help. That shuddering, sometimes in the dark you can see if the (secondary) voltage from the coil is intermittently finding an easier way to get to ground than the plug- gap/wire. Sometimes you see it, or you might hear the snap. Right now I'm not sure where I have any metal vacuum lines on my two 89=90 Jeeps...rearward to the tank for e-vap I suppose.

 

Interesting.. Well the line definitely heads back to the tank. I found it dangling just by the e-vap canister. But, I didn't see anywhere it would go.

 

Have you been to my website and completed Tips 1,3,4, and 5 yet?

 

Hey there, Cruiser. I have done 1, 3, and 4. I will do tip 5 tomorrow, and report back.

 

I gather the Evap canister only gets vacuum from the intake tube to the throttle body via a venturi, can't be a real vacuum leak. That gentle suction can draw vapor from the tank through the canister to be fed to the engine. A very non invasive/harmless smog thing that's just putting "HC's", Hydrocarbons, (un-burnt fuel), into the engine.

 

Hey Cruiser, I just completed tip 5. All seems good. The resistance measured between the two probes on the multimeter read 1.3. The resistance between the negative post and the TPS was about 1.4, with no variation when wiggling the wiring harness. When driving to the gym and back today, it felt okay. No overly noticeable stumbling/hesitation like yesterday. I am on 3.55 gears with 33'' tires, so it's no sports car. However, the last few days I definitely feel like it has less power than usual. When merging on the freeway, just feels like it is missing some power. Doesn't want to get into 2nd gear like it normally does when I floor it. If it does, it just feels like there's less movement than usual. I noticed sometimes when I drop it into gear from park, it will feel like it wants to bog down for a couple seconds. The hesitation yesterday was concerning. Just barely on the throttle through a parking lot, it would just cut in and out, and I thought it was going to die.