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Discussion Starter · #1 · (Edited)
ETA: update below.



(87-90 2.5) I see a few old threads about "intake air temp sensor" and "air charge sensor" replacement. Are they the same thing? If so, how many are there? If they're not the same thing, which is which? Or what's whay in this photo? A tad cornfuzed.

 

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Discussion Starter · #3 ·
After posting this last night I saw them listed somewhere under both names together, so I guess they're the same thing. But most of the posts I've read seem to mention one, not two. (though that doesn't have to mean anything)

Don't know that I need them, just grasping at causes for my fouling rear two spark plugs)
 

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Discussion Starter · #5 · (Edited)
Black, dry. Not frequently, it's fouling them immediately. Put new plugs in, go for a drive, pull them and they're black. This only started after I changed the head gasket.

Seems to drive fine. Idles poorly, sometimes very. Uneven, a clear miss. Exhaust sounds odd. "Uneven" feel to it, one pulse is clearly a lot stronger than the rest. Shop that milled the head also "fixed" an issue with one valve not seating. I don't know now if that was #2 or #3, didn't catch the orientation on the bench. Plug 3 & 4 are fouling. Starting to wonder if they missed something else, there was more wrong than they found. Or they just screwed up (wouldn't be the first time). Compression test I did many weeks ago didn't show anything unusual.

I was looking for "cheap" possibilities to throw at it before I tear the head off again. I changed all the vac lines (which needed it anyway) MAP, O2, plugs several times, cap, rotor, wires even though they were all less than two years old. Changed them all hoping/wondering if the miss would go away and was unrelated to the fouling. Seems not.

But just two fouling on a TBI doesn't make sense to me as far as a sensor being the cause. How could it effect just half the intake manifold? I haven't come up with any intake leaks where it meets the head. Initially I was thinking a sensor or some sort as I THOUGHT it seemed to start and idle fine in open loop, then poorly once it switched to closed. But that doesn't seem to be the case now.


On my original question, is started me thinking... where is the engine water temp sensor? I know the one on the top of the head, but that's for the gauge on the dash. Where does the ECU get it from? Is that what the top one in the photo is? (I haven't pulled it, I guess I could and see if antifreeze comes out lol)
 

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Discussion Starter · #7 ·
That's just a photo stolen from the net, but it's the same. That fitting at the 9 o'clock in the photo is a coolant line.
 

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Discussion Starter · #8 · (Edited)
I came close to ordering a new head last night and this morning. I intended to do so when I got to work. But I thought, no, hold out and check one more thing, one more time.

Dry black shoot... probably meaning running rich. But how can two cylinders in a TBI setup be getting too much fuel? Would a cracked manifold cause that? Then I started to think, what if they're only getting too much fuel because it's adjusting to the other two getting too much air?
I'd already checked for intake leaks spraying everything with carb cleaner, brake cleaner, WD-40, never any change in how it ran. Tonight I used a propane torch. Turned the gas on and stuck it right where the front two intake runners meet the head. And when I did, the miss went away. I checked it a couple times and each time the miss went away and came back as soon as I took it away. M'erF'er! This puzzles me, as I was using a timing light to see if I could isolate the miss to one cylinder, and it was only on the rear two that I'd get the occasional missed beat.

I pulled the intake off tonight. I'll give it a going over. Maybe add some stick'em tween the gasket and it's adjoining parts. Here's hoping.

I need to get this solved because my clutch slave it dying. When I pull the tranny to fix that, I need to repair the center section of the frame that I stupidly forgot about and didn't do when I did the rear frame repairs spring before this one. Cant start that till I know the engine is okay. One catastrophe at a time.
 

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Discussion Starter · #13 ·
All back together yesterday. At the moment, all is right. Idles as it used to, maybe better. Runs good. Exhaust sounds "normal". Smells a whole lot better.

I can't really describe the exhaust sound driving, or more importantly decelerating or down shifting. But before, the sound it made, I can only describe it as the having the same sound a the tuned Subaru's do. It was embarrassing. :D That hollow "Putter-dutter-dutter-dutter-dutter" sound. (I guess only half the sound though, because only half the engine was doing it, but it was that exact same sound)
 
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