AnotherOldJeepGuy

Looks like I might need to replace this, so it would be helpful if you could note back if you were able to get to this without removing other things, or, what other things you had to remove to get to it!

@M.T.Hands posted back in 2024 that he fixed his regulators. I followed the post so I went back and looked at it, but I don't see any info on how in that post. I remember someone talking about swapping the spline end to end and getting the bad part moved to where it didn't count, but I don't remember where that information is. The first time mine started doing this I was able to clean in good in place and oil it up, and that fixed it for maybe a couple years, so that might work for you depending on the amount of wear. The last time mine started to act up the only thing I managed to do was to literally block the window from going all the way down, which was where the failure was. Not a great fix but a functional band-aid that kept me or a passenger from accidentally lowering it to a point I could not get it raised back up. Good luck and if you find a source of good replacements please post it!

I went back through reading about the EGR because I am still curious about the EGR movement not being consistent. Reading back through I realized I didn't answer this post questions. I don't know that anything smells any different, if so it's not obvious to me. I don't have anyone handy to rev for me, but I'll see if I can get my neighbor to do it when he gets home from work. I'm still curious why my EGR moves only sometime when I rev up, and when it does move is when I get the backfire and the delay to accel, and want to stall, when neither happen when it doesn't move.

I measure ~2060. It's been roughly 2 hours since I had the engine on for about 4 minutes, and the exhaust feels cool, so I'm assuming that is cool enough. I don't have a 10k scale choice, all I have is ohm, k-ohm, m-ohm, so I used k-ohm setting. I remeasured on auto-scale and got the same value. So for sure not open or 30k+, but perhaps low. I guess maybe I should watch temp with the REM and see if ECU is getting reasonable values before I replace this sensor, especially since I don't know how much stuff is in the way for replacing it. I started up with sensor disconnected just to see what it did, it ran just the same at start up as with it connected. I only let it run about a minute not knowing what damage I might do.

Wow, talk about redundancy! 3 Fluid Temp sensors! Overheating if it happens could for sure be a big deal so other than 3 failure opportunities, having 3 sounds fine with me!

Did soap test #1 at the donut. Didn't see any bubbles on first test. But I can only test a little at a time since I have to catch it on my phone. Got about 2 minutes max before it was hot enough to evap the soap. https://drive.google.com/file/d/1UWBtZNOYjkVmAVcxKzix_9CgiTkAnvvP/view?usp=sharing Wasn't a 100% test, I don't think I got soap all the way around so I'll try again, after it cools off. This is the CTS correct? Looks like a single wire so I measure between the connector and chassis?

Understood. Good to know. This one has been working from Feb 2025 though. But I wish I still had to old one to swap back in, since the issue back then didn't turn out to be the sensor, just to rule out it has not failed.

Vacuum plug back in place and hose tied off so it doesn't wander... Pulled Dist Cap, the rotor only wiggled back and forth a tiny bit, maybe 1-2 degrees each way, very small. Things looked pretty much the same shape as when installed in Jan. Not pristine, but pretty clean. Still no soap test, but I did give the manifold to exhaust donut the slight poke test. It's not in very good shape, I am pretty sure if I upped the poke pressure I could cause it to crumble. Maybe not 100% but for sure a notable amount. Perhaps it would be worth just replacing it to rule that out? I figure if I end up working on the exhaust manifold I'd be replacing that anyway. I'd thing the cost is minimal for a new gasket. Assuming the rusty bolts will let loose, I am wondering if the donut can be replaced without removing much else? The pipe wanders around from there to the CAT, and I don't see any anchors, and I see maybe an inch of space between the pipe and the frame, would that be enough slack? It's worth confessing that I have been reluctant to crawl around under the truck while leaving it running with no other human in the cab to cut the engine and hold the brakes. But I have stuck my head under a little to try and locate from where the loud comes from but difficult to pinpoint.

Gotcha, I was assuming I would need some kind of tool to check for "inadequate" spark.

AFAIK I don't have a Check Engine lamp, I've never seen one in over the last 36 years that I can recall (which in most cases would be a good thing ). I looked in my manual and it doesn't identify one existing at least not in the instrument cluster. The closest thing seems to be the Engine Maint light that apparently went on at 82,500 miles, that was way too long ago for me to remember it, but I assume it did. I replaced this sensor back in Feb 2025 when I had an idle issue. The issue turned out to be very dirty TB and IAC and was completely resolved after cleaning them and putting in a new TB gasket. Of course it could still be contributing, just not because of age. I'll give that a shot! Have not coordinated with my son on the soap cannon yet for the bubble test but hopefully can get that done pretty soon. I'm guessing I would need another tool I don't have to test this.... correct? Thanks for all the assistance so far!

Got the tool from Harbor Freight and measured the pressure at the fuel rail. FPR hose attached = 30PSI FPR hose not attached = 37PSI

Heading out to get the tools for checking the fuel pressure.....

The battery reset didn't change the outcome, still sluggish response to throttle and running very choppy. My son has a thing called a soap cannon he uses to was his car. I'm gonna see if he will bring in over and let me use it to suds up the exhaust real good and see if any bubbles show up. Think I'll need to do that first thing in the morning when it's as cool as it gonna get since the exhaust is gonna dry out pretty fast once the motor is running, but just maybe I'll see something useful.

I made the "plug" below. The bolt is in very tight to start then snugged further with 2 tie wraps. I don't know that this was a 100% plug but it should be very close to it. (I can redo it with come E6000 glue if it doesn't look like it is OK as is). With this one the vacuum port (but before reading your post about resetting by disconnecting the battery) I saw no change. Sluggish response to throttle, running choppy, and at least once when I got the RPMs up and let go I got a small backfire (similar to the one I posted a video of a page back). I'll go disconnected the battery and repeat the test.

Oh, didn't realize the test went farther than just seeing what happened just when plugging it. I'll come up with something to plug it other than my thumb and see what happens when I drive in a little. As far as cruise, I can't remember the last time that worked, but it is measured in years not weeks!

OK, I don't know if this counts as a V8 moment or not but here's what I observed. 1. Started with hose still connected and listened for a base for comparison 2. Pulled the hose off - RPM increased a bit, not a huge amount but noticeable. 3. Plugged the manifold port with my thumb, engine returned to about the same as with the hose connected. (I didn't really have anything that would qualify as a vacuum plug but thumb seemed to do the job) So the blocked port compared to the hose connected sounded the same. FWIW, as I reattached the hose, just before making contact, I could hear noticeable sucking sound so it is pulling a vacuum. I don't have anything to measure with, but it's there.

I will definitely give this a try tomorrow and post what happens. I got sidetracked today with appointment so I haven't gotten the vacuum tester yet either, but hopefully tomorrow. Haven't tried my soapy water test yet either so plenty of what-ifs on the list to do.

That's "a few" ! lol

How would running rich be noticed? What kind of performance issues might be noticed if the engine is running rich?

Finished with removing and inspecting plugs assignment . They all looked the same. I cleaned them all and put them back in (well new one for the one with broken top), no change in how the truck runs. Planning to get my hands on some kind of pressure measurement gear tomorrow.

If I don't find a loaner, would this from Harbor Freight work? https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html

Thanks @Gojira94, @Porquer. Since I broke a plug I'll go ahead and replace it, there's not a lot of choice on that one. For the others, a pic of one cleaned up is below. I'm thinking cleaning and reinstall is good enough at least for now, the plugs were all new in Jan. I'll be calling the local auto places today to see if a fuel pressure checker can be borrowed or rented so that data point can be added to the collection. As for the elusive yet suspected leak, perhaps the soapy water test (the one used to find a tire leak) might work at least at the donut gasket? Not sure access/visibility is really good enough for that test elsewhere, but maybe I can do it at the donut.

FWIW, Here's the parts catalog page for the 2.5. (Half the time I can't find what I am looking for in these, but might have gotten lucky this time ) Of course having a part number doesn't mean the part is actually available and you may still have to be creative like @eaglescout526!

Here are the OEM part numbers, maybe searching for the 87 ones.

I got mine at NAPA, although I have 1990. But you might check there.